This work was supported by National Institutes of Health/National Institute of Neurological Disorders &#38; Stroke (NIH/NINDS) grants R01-NS074387, R01-NS057711 and R21-NS091555 to M.G.C.; NIH/NINDS grants R01-NS061107, R01-NS076991, R01-NS082311 and R21-NS084275 to P.R.L.; grants from Leah&#8217;s Happy Hearts, University of Michigan Comprehensive Cancer Center awarded to M.G.C. and P.R.L; the Department of Neurosurgery, University of Michigan School of Medicine; the Michigan Institute for Clinical and Health Research, supported by NIH grant 2UL1-TR000433; the University of Michigan Cancer Biology Training Grant supported by NIH/NCI (National Cancer Institute) grant T32-CA009676; the University of Michigan Training in Clinical and Basic Neuroscience supported by NIH/NINDS grant T32-NS007222; and the University of Michigan Medical Scientist Training Program supported by NIH/NIGMS (National Institute of General Medicine Sciences) grant T32-GM007863. The authors are thankful for the academic leadership and support received from Dr. Karin Muraszko and the Department of Neurosurgery; to M. Dahlgren, D. Tomford, and S. Napolitan for superb administrative support; to M. Dzaman for outstanding technical assistance; and to Phil F. Jenkins for generous support toward the purchase of a Zeiss 3D Scanning Electron Microscope. We also acknowledge the Kuchroo laboratory at Harvard Medical School from which a modified version of the density centrifugation media-mediated strategy for isolation of brain mononuclear cells was drawn.

<ol>
	<li>Bleeker, F. E., Molenaar, R. J., Leenstra, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+the+molecular+understanding+of+glioblastoma.">Recent advances in the molecular understanding of glioblastoma.</a> J Neurooncol. 108, 11-27 (2012).</li><li>Stupp, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Radiotherapy+plus+concomitant+and+adjuvant+temozolomide+for+glioblastoma.">Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma.</a> N Engl J Med. 352, 987-996 (2005).</li><li>Ostrom, Q. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CBTRUS+statistical+report:+primary+brain+and+central+nervous+system+tumors+diagnosed+in+the+United+States+in+2007-2011.">CBTRUS statistical report: primary brain and central nervous system tumors diagnosed in the United States in 2007-2011.</a> Neuro Oncol. 16, iv1-63 (2014).</li><li>Louveau, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+and+functional+features+of+central+nervous+system+lymphatic+vessels.">Structural and functional features of central nervous system lymphatic vessels.</a> Nature. 523, 337-341 (2015).</li><li>Kennedy, B. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumor-associated+macrophages+in+glioma:+friend+or+foe?.">Tumor-associated macrophages in glioma: friend or foe?.</a> J Oncol.. 2013, 486912 (2013).</li><li>Markovic, D. S., Glass, R., Synowitz, M., Rooijen, N., Kettenmann, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia+stimulate+the+invasiveness+of+glioma+cells+by+increasing+the+activity+of+metalloprotease-2.">Microglia stimulate the invasiveness of glioma cells by increasing the activity of metalloprotease-2.</a> J Neuropathol Exp Neurol. 64, 754-762 (2005).</li><li>Zhai, H., Heppner, F. L., Tsirka, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia/macrophages+promote+glioma+progression.">Microglia/macrophages promote glioma progression.</a> Glia. 59, 472-485 (2011).</li><li>Kmiecik, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elevated+CD3++and+CD8++tumor-infiltrating+immune+cells+correlate+with+prolonged+survival+in+glioblastoma+patients+despite+integrated+immunosuppressive+mechanisms+in+the+tumor+microenvironment+and+at+the+systemic+level.">Elevated CD3+ and CD8+ tumor-infiltrating immune cells correlate with prolonged survival in glioblastoma patients despite integrated immunosuppressive mechanisms in the tumor microenvironment and at the systemic level.</a> J Neuroimmunol. 264, 71-83 (2013).</li><li>Yang, I., Han, S. J., Sughrue, M. E., Tihan, T., Parsa, A. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immune+cell+infiltrate+differences+in+pilocytic+astrocytoma+and+glioblastoma:+evidence+of+distinct+immunological+microenvironments+that+reflect+tumor+biology.">Immune cell infiltrate differences in pilocytic astrocytoma and glioblastoma: evidence of distinct immunological microenvironments that reflect tumor biology.</a> J Neurosurg. 115, 505-511 (2011).</li><li>Wagner, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglial/macrophage+expression+of+interleukin+10+in+human+glioblastomas.">Microglial/macrophage expression of interleukin 10 in human glioblastomas.</a> Int J Cancer. 82, 12-16 (1999).</li><li>El Andaloussi, A., Lesniak, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+increase+in+CD4+CD25+FOXP3++regulatory+T+cells+in+tumor-infiltrating+lymphocytes+of+human+glioblastoma+multiforme.">An increase in CD4+CD25+FOXP3+ regulatory T cells in tumor-infiltrating lymphocytes of human glioblastoma multiforme.</a> Neuro Oncol. 8, 234-243 (2006).</li><li>Kostianovsky, A. M., Maier, L. M., Anderson, R. C., Bruce, J. N., Anderson, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Astrocytic+regulation+of+human+monocytic/microglial+activation.">Astrocytic regulation of human monocytic/microglial activation.</a> J Immunol. 181, 5425-5432 (2008).</li><li>Curtin, J. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HMGB1+mediates+endogenous+TLR2+activation+and+brain+tumor+regression.">HMGB1 mediates endogenous TLR2 activation and brain tumor regression.</a> PLoS Med. 6, e10 (2009).</li><li>Curtin, J. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fms-like+tyrosine+kinase+3+ligand+recruits+plasmacytoid+dendritic+cells+to+the+brain.">Fms-like tyrosine kinase 3 ligand recruits plasmacytoid dendritic cells to the brain.</a> J Immunol. 176, 3566-3577 (2006).</li><li>Mineharu, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+the+brain+tumor+microenvironment+enhances+the+efficacy+of+dendritic+cell+vaccination:+implications+for+clinical+trial+design.">Engineering the brain tumor microenvironment enhances the efficacy of dendritic cell vaccination: implications for clinical trial design.</a> Clin Cancer Res. 17, 4705-4718 (2011).</li><li>Larocque, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exogenous+fms-like+tyrosine+kinase+3+ligand+overrides+brain+immune+privilege+and+facilitates+recognition+of+a+neo-antigen+without+causing+autoimmune+neuropathology.">Exogenous fms-like tyrosine kinase 3 ligand overrides brain immune privilege and facilitates recognition of a neo-antigen without causing autoimmune neuropathology.</a> Proc Natl Acad Sci U S A. 107, 14443-14448 (2010).</li><li>Curtin, J. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Treg+depletion+inhibits+efficacy+of+cancer+immunotherapy:+implications+for+clinical+trials.">Treg depletion inhibits efficacy of cancer immunotherapy: implications for clinical trials.</a> PLoS One. 3, e1983 (2008).</li><li>Ali, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combined+immunostimulation+and+conditional+cytotoxic+gene+therapy+provide+long-term+survival+in+a+large+glioma+model.">Combined immunostimulation and conditional cytotoxic gene therapy provide long-term survival in a large glioma model.</a> Cancer Res. 65, 7194-7204 (2005).</li><li>Dewey, R. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+brain+inflammation+and+persistent+herpes+simplex+virus+1+thymidine+kinase+expression+in+survivors+of+syngeneic+glioma+treated+by+adenovirus-mediated+gene+therapy:+implications+for+clinical+trials.">Chronic brain inflammation and persistent herpes simplex virus 1 thymidine kinase expression in survivors of syngeneic glioma treated by adenovirus-mediated gene therapy: implications for clinical trials.</a> Nat Med. 5, 1256-1263 (1999).</li><li>Baker, G. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Natural+killer+cells+eradicate+galectin-1-deficient+glioma+in+the+absence+of+adaptive+immunity.">Natural killer cells eradicate galectin-1-deficient glioma in the absence of adaptive immunity.</a> Cancer Res. 74, 5079-5090 (2014).</li><li>Baker, G. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+glioma+formation:+iterative+perivascular+glioma+growth+and+invasion+leads+to+tumor+progression,+VEGF-independent+vascularization,+and+resistance+to+antiangiogenic+therapy.">Mechanisms of glioma formation: iterative perivascular glioma growth and invasion leads to tumor progression, VEGF-independent vascularization, and resistance to antiangiogenic therapy.</a> Neoplasia. 16, 543-561 (2014).</li><li>Ormerod, M. G., Novo, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Flow cytometry : a basic introduction. , (2008).</li><li>Stirling, D. P., Yong, V. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamics+of+the+inflammatory+response+after+murine+spinal+cord+injury+revealed+by+flow+cytometry.">Dynamics of the inflammatory response after murine spinal cord injury revealed by flow cytometry.</a> J Neurosci Res. 86, 1944-1958 (2008).</li><li>Hirai, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+prevalence+and+phenotype+of+activated+microglia/macrophages+within+the+spinal+cord+of+the+hyperostotic+mouse+(twy/twy)+changes+in+response+to+chronic+progressive+spinal+cord+compression:+implications+for+human+cervical+compressive+myelopathy.">The prevalence and phenotype of activated microglia/macrophages within the spinal cord of the hyperostotic mouse (twy/twy) changes in response to chronic progressive spinal cord compression: implications for human cervical compressive myelopathy.</a> PLoS One. 8, e64528 (2013).</li><li>Fleming, T. J., Fleming, M. L., Malek, T. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+expression+of+Ly-6G+on+myeloid+lineage+cells+in+mouse+bone+marrow.+RB6-8C5+mAb+to+granulocyte-differentiation+antigen+(Gr-1)+detects+members+of+the+Ly-6+family.">Selective expression of Ly-6G on myeloid lineage cells in mouse bone marrow. RB6-8C5 mAb to granulocyte-differentiation antigen (Gr-1) detects members of the Ly-6 family.</a> J Immunol. 151, 2399-2408 (1993).</li><li>Wiesner, S. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=De+novo+induction+of+genetically+engineered+brain+tumors+in+mice+using+plasmid+DNA.">De novo induction of genetically engineered brain tumors in mice using plasmid DNA.</a> Cancer Res. 69, 431-439 (2009).</li><li>Holland, E. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combined+activation+of+Ras+and+Akt+in+neural+progenitors+induces+glioblastoma+formation+in+mice.">Combined activation of Ras and Akt in neural progenitors induces glioblastoma formation in mice.</a> Nat Genet. 25, 55-57 (2000).</li><li>Lynes, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lentiviral-induced+high-grade+gliomas+in+rats:+the+effects+of+PDGFB,+HRAS-G12V,+AKT,+and+IDH1-R132H.">Lentiviral-induced high-grade gliomas in rats: the effects of PDGFB, HRAS-G12V, AKT, and IDH1-R132H.</a> Neurotherapeutics. 11, 623-635 (2014).</li><li>de Vries, N. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+and+robust+transgenic+high-grade+glioma+mouse+models+for+therapy+intervention+studies.">Rapid and robust transgenic high-grade glioma mouse models for therapy intervention studies.</a> Clin Cancer Res. 16, 3431-3441 (2010).</li><li>Uhrbom, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ink4a-Arf+loss+cooperates+with+KRas+activation+in+astrocytes+and+neural+progenitors+to+generate+glioblastomas+of+various+morphologies+depending+on+activated+Akt.">Ink4a-Arf loss cooperates with KRas activation in astrocytes and neural progenitors to generate glioblastomas of various morphologies depending on activated Akt.</a> Cancer Res. 62, 5551-5558 (2002).</li><li>Marumoto, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+novel+mouse+glioma+model+using+lentiviral+vectors.">Development of a novel mouse glioma model using lentiviral vectors.</a> Nat Med. 15, 110-116 (2009).</li><li>Assanah, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glial+progenitors+in+adult+white+matter+are+driven+to+form+malignant+gliomas+by+platelet-derived+growth+factor-expressing+retroviruses.">Glial progenitors in adult white matter are driven to form malignant gliomas by platelet-derived growth factor-expressing retroviruses.</a> J Neurosci. 26, 6781-6790 (2006).</li></ol>

The authors have nothing to disclose.

This protocol describes a robust and reproducible method for the isolation and flow cytometric analysis of PBMCs that have infiltrated the early mouse brain tumor microenvironment. Glioma cell suspensions are generated at a concentration specified by the experimentalist that are stereotactically engrafted into the striatum of the mouse brain. Mice are then euthanized at predetermined time points specified by the experimental design and their brains are harvested and processed to isolate glioma-infiltrating PBMCs which are immunolabeled with combinations of fluorochrome-conjugated primary antibodies; immunolabeled cells are then quantified by flow cytometry. Although the demonstration presented here focuses on early time points, glioma-infiltrating PBMCs can be assessed at any time point post-tumor engraftment up until mouse moribundity. The method is highly modular as any number of different antibody combinations may be used to examine immune cells of interest including T cells, B cells, NK cells, monocytes, and macrophages. Note that the protocol has been optimized for use with female C57BL/6J mice 8-10 weeks of age. Mice outside of this age range may have altered percentages of circulating PBMCs, which may lead to cell counts at equivalent time points that are not representative of the data presented here. Characterization experiments may also be required if alternative tumor models are used or if mice other than those on the B6 background are used due to the fact that strains can differ in their PBMC profiles (Jaxpheno6; Mouse Phenome Database; the Jackson Laboratory). Gender and environmental conditions can also be sources of disparity among PBMC frequencies and percentages.
This method has been demonstrated using a combination of four cell surface antibodies that enable the detection of Gr-1+/CD11b+ myeloid cells and NK1.1+ NK cells, cell types implicated in the rejection of gal-1-deficient glioma. The inclusion of intracellular GzmB antibodies further enables the detection of cytotoxic potential in the NK cell subset. Representative results are provided for immune cell infiltration into early GL26-Cit gliomas in syngeneic C57BL/6J mice that either express normal levels of gal-1 or which have reduced levels due to shRNA-mediated gene knockdown. The demonstration exhibits the sensitivity and reproducibility of the technique by showing that glioma-infiltrating PBMCs can be reproducibly isolated and quantified as soon as 24 hr post-tumor engraftment. Aside from revealing a population of tumor-infiltrating Gr-1high/CD11b+ myeloid cells, the demonstration also reveals a population of Gr-1int./CD11b+ cells whose identity is currently undefined; additional experiments are necessary to further decipher the character of this cell population. We also note that we do not observe a readily distinguishable population of CD45int/Gr-1-/CD11bhigh/NK1.1-&#160;cells consistent with microglia as previously described by others23,24. A simple explanation for this result is that the specific isolation protocol used here precludes their accumulation at the 37/70 density centrifugation media interface. It is also important to point out that the cells collected from the 37/70 density centrifugation interface do not appear to include the glioma cells themselves. This is evident by the fact that GL26-Cit glioma cells, which appear between 100-200K on SSC-A and 100K of FSC-A using equivalent PMT voltages to those used in this demonstration (data not shown) are absent from the FSC-A vs. SSC-A plots (refer to Figure 5A; Step 1).
Anti-Gr-1 antibodies recognize both the Ly6G and Ly6C cell surface proteins that are specific to polymorphonuclear and mononuclear myeloid cells, respectively25. The use of anti-Gr-1 antibodies thus precludes distinction between these two cell populations. Preliminary results in our lab are now beginning to shed light on a more accurate description of the early Gr-1+/CD11b+ cells that infiltrate the gal-1-deficient glioma microenvironment. Experiments incorporating anti-Ly6G (clone: 1A8) and anti-Ly6C (clone: AL-21) antibodies together with anti-CCR2 antibodies now indicate that the Gr-1high/CD11b+ cells infiltrating the early gal-1-deficient tumor microenvironment are consistent with Ly6Chigh/CCR2high inflammatory monocytes, although further experiments are required to confirm this result (data not shown).
Due to cell loses that may occur during the repeat centrifugation and resuspension steps involved in isolating glioma-infiltrating PBMCs, it is likely that observed cell counts are in fact lower that what are actually present in the intact brain. However, differences between experimental groups should hold if equivalent volumes of the 37/70 density centrifugation media interface are extracted and if the entire volume of each sample is analyzed by the flow cytometer. Failure to adhere to these steps will result in unfair comparisons between samples and will preclude unbiased analysis. The inability to quantify the exact number of PBMCs entering the brain tumor microenvironment is not a limitation specific to this protocol. Alternative methods such as immunohistological cell counting strategies are also subject to error due to extrapolations of total cell numbers based on stereological counts and the requirement of equivalent image thresholding on tissue section micrographs, which may differ in their level of background staining, potentially leading to false-negative or false-positive signals. Nevertheless, a comparison of time course analysis between different analytical methods should reveal time-dependent immune-influx curves with similar overall shape. An additional drawback to immunohistochemical methods is the inability of certain antibodies validated for flow cytometry to bind to the equivalent antigenic epitope in the context of formalin-fixed brain tissue sections.
There are a few key steps in this protocol that may serve as limitations for those unfamiliar with its methodology. One such step is the harvesting of the brain from the cranium without damaging it. We suggest practicing the technique several times prior to running proper experiments. However, since the brain will eventually be triturated, minor damage to the superficial layers of the brain are likely inconsequential to the accurate quantification of glioma-infiltrating PBMCs. A second step that inexperienced investigators may initially find difficult is the pouring of the density centrifugation media gradient. The experimentalists&#8217; ability to form a clean interface while overlying the 2 ml of 37% density centrifugation media on top of the 70% layer is crucial to reproducible isolation of PBMCs. Although this step may initially prove challenging, it vastly enriches for PBMCs and dramatically decreases the period of time otherwise required for sample analysis if whole brain tissue where to be analyzed flow cytometrically. PBMC enrichment also reduces the total number of events captured by the flow cytometer, thus reducing .fcs file sizes and helping to resolve rare brain-infiltrating immune cell populations. For best results in establishing a clean density centrifugation interface we recommend pouring the 37% density centrifugation media using a P-1000 micropipette with smooth plunger action. Angle the 15 ml centrifuge tube approximately 20-30&#176; above the bench top. Rest the tip of the micropipette on the side of the tube 3-5 ml markings above the surface of the 70% density centrifugation media layer. Pour steadily and slowly so to minimize overt outward momentum of the 37% density centrifugation media as it extrudes from the micropipette tip in order to avoid disturbing the underlying 70% density centrifugation media. Lastly, the fact that the brain tissue architecture is necessarily destroyed in the process of isolating glioma-infiltrating PBMCs means that additional mice will be required to obtain time point matched histological data.
Newer glioma models generated through the injection of oncogenic plasmid DNA into the normal rodent brain have been developed in recent years26-32. These &#8220;endogenous&#8221; tumor models circumvent potential artifacts caused by stereotactically engrafting ex vivo cancer cells and more closely mimic the histological hallmarks of clinical glioma. The method described herein is well suited to the study of immune infiltration events that characterize these more clinically relevant model systems. Studies on immune influx in neonatal mice may also be performed using this method although the density of neonatal mouse brain is less than that of adults, which may require an optimization of the enzymatic digestion step in order to prevent over digestion of the brain tissue. Additional applications of the technique include investigations on alternative classes of inflammatory brain disease aside from malignant tumors such as experimental allergic encephalomyelitis (EAE) and immune responses to viral infection.

Gliomas are a class of neuroepithelial brain cancers arising from transformed glia within the central nervous system (CNS). Of all the gliomas, World Health Organization (WHO) grade IV glioma, or glioblastoma (GBM), is the most common and lethal1. GBM is highly refractory to the current standard-of-care which consists of tumor resection to the extent possible followed by radiation plus concomitant and adjuvant chemotherapy with temozolomide2. These deadly cancers carry a dismal prognosis of only 15-18 months of survival from the time of initial diagnosis with only 5% of patients surviving the disease after 5 years3.
The presence of the blood brain barrier (BBB), lack of professional antigen presenting cells (APCs), and the previously unidentified existence of bona fide lymphatic structures within the brain4 have led to the notion of GBM as immune privileged. However, numerous studies now show that these brain cancers indeed engender the recruitment of peripheral immune cells that are predominantly myeloid in origin which include monocytes, macrophages, and myeloid-derived suppressor cells (MDSCs)5. GBM also influences the activity of brain-resident microglia to become pro-tumorigenic6,7. Lymphoid cells such as CD8+ T cells8 and CD56+&#160;natural killer&#160;cells9 are also present within the tumor microenvironment, but in much fewer numbers, a fact thought to be due to immunosuppressive function instigated by glioma-derived factors on tumor associated macrophages (TAMs)10. CD4+ T cells are also present in GBM, but much of this population also expresses CD25 and FoxP3, makers of immunosuppressive T regulatory (Treg) cells11. The overall immunosuppressive state of GBM culminates in the promotion of immunologic escape and tumor progression12.
A better understanding of the mechanisms of GBM immunosuppression is critical to the development of effective immunotherapeutic strategies designed to stimulate the immune system against the tumor. Over the last 15 years our lab has worked to overcome the mechanisms of brain tumor immunosuppresson in order to develop efficacious new anti-GBM immunotherapeutics13-19. The culmination of this work has now led to a clinical trial designed to evaluate a combined cytotoxic and immune-stimulatory therapeutic for patients with newly diagnosed GBM (ClinicalTrials.gov Identifier: NCT01811992).
Our most recent work shows that mouse GL26 and rat CNS-1 GBM cells block anti-tumor NK cell immune surveillance by producing large amounts of the &#946;-galactoside-binding lectin galectin-1 (gal-1)20. This was demonstrated by suppressing the expression of gal-1 in glioma cells using shRNA-mediated gene knockdown. In vitro experiments showed that gal-1-deficient glioma cells proliferated normally in culture, yet underwent rapid rejection soon after intracranial engraftment into syngeneic C57BL/6J or RAG1-/- mice, thus establishing the independence of T- or B- cells on this form of tumor rejection. NK cell immunodepletion with anti-asialo GM1 anti-serum or monoclonal NK1.1 antibodies led to the complete restoration of intracranial gal-1-deficient glioma growth, establishing the role of NK cells in gal-1-deficient glioma rejection. We now show that immunodepletion of Gr-1+/CD11b+ myeloid cells is sufficient to prevent gal-1-deficient glioma rejection despite the presence of NK cells, thus revealing a indispensible auxiliary role for myeloid cells in the aiding of NK-mediated gal-1-deficient tumor lysis (unpublished data). This unexpected result has led us to develop a comprehensive protocol for the isolation and analysis of peripheral blood mononuclear cells (PBMCs) that infiltrate the brain tumor microenvironment soon after intracranial engraftment so that we may better characterize the immune infiltration events that predicate gal-1-deficient glioma rejection.
The method is demonstrated here by using mouse GL26 glioma cells that constitutively express mCitrine fluorescent protein, called GL26-Cit, which permit direct tumor cell visualization by fluorescence microscopy21. These cells are stereotactically engrafted into the brain of syngeneic C57BL/6J mice and are allowed to grow for 24, 48, or 72 hr prior to mouse euthanasia. Glioma-infiltrating PBMCs are then isolated and immunolabeled using anti -CD45, -Gr-1, -CD11b and -NK1.1 cell surface antibodies together with intracellular immunolabeling for granzyme B (GzmB). This specific combination of antibodies allows for the identification of tumor-infiltrating Gr-1+/CD11b+ myeloid cells and NK1.1+, NK cells, cell types we&#160;have been implicated in gal-1-deficient tumor rejection. The immune infiltration profile of gal-1-deficient GL26-Cit glioma, referred to here as GL26-Cit-gal1i, is then compared to that of gliomas expressing normal levels of gal-1 called GL26-Cit-NT that contain a non-targeting control shRNA hairpin. The protocol begins with a description on how to culture GL26-Cit glioma cells in vitro, which is followed by an explanation on how to orthotopically engraft these cells into the striatum of syngeneic C57BL/6J mice. It then proceeds to enumerate the steps involved in the isolation and immunolabeling of glioma-infiltrating PBMCs for flow cytometric analysis. The protocol concludes with an explanation of standard data analysis and graphical representation.
The demonstration reveals that both Gr-1+/CD11b+ myeloid cells and NK1.1+ NK cells preferentially accumulate within the gal-1-deficient brain tumor microenvironment within 48 hr of tumor implantation, a result which helps explain why these tumors rapidly undergo complete tumor lysis approximately 1 week post-tumor engraftment20. The method is easily adaptable to a number of different in vivo experimental designs in which temporal data on immune infiltration into the brain is required. A single experimentalist can perform the protocol from brain harvesting to flow cytometric analysis of glioma-infiltrating PBMCs in about 4-6 hr depending on the number of samples to be analyzed. The method may also be combined with experiments aimed to characterize the profile of circulating PBMCs in tumor bearing mice for comparison with those that infiltrate the brain so to identify immunosuppression phenotypes specifically induced by the tumor microenvironment. Application of this and similar methods should facilitate a better understanding of the factors involved in the trafficking of peripheral immune cells into the brain tumor microenvironment.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Dulbecco&#8217;s Modification of Eagles Medium</td>
			<td>Gibco</td>
			<td>12430-054</td>
			<td>with 4.5g/L D-glucose, L-glutamine, 25mM HEPES and phenol red&#160;</td>
		</tr>
		<tr>
			<td>Dulbecco&#8217;s Phosphate-buffered Saline&#160;</td>
			<td>Gibco</td>
			<td>14190-144&#160;</td>
			<td>without calcium chloride or Magnesium chloride</td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>Omega Scientific Inc.</td>
			<td>FB-11</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin Streptomycin&#160;</td>
			<td>Gibco</td>
			<td>15140-122</td>
			<td>10,000U/ml Penicillin; 10,000&#956;g/ml Streptomycin&#160;</td>
		</tr>
		<tr>
			<td>L-glutamine</td>
			<td>Gibco</td>
			<td>25030-081</td>
			<td>200mM</td>
		</tr>
		<tr>
			<td>G418 sulfate&#160;</td>
			<td>Omega Scientific Inc.</td>
			<td>GN-04</td>
			<td></td>
		</tr>
		<tr>
			<td>Puromycin dihydrochloride&#160;&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>P8833</td>
			<td>from Streptomyces alboniger</td>
		</tr>
		<tr>
			<td>HyClone HyQTase non-mammalian trypsin alternative&#160;</td>
			<td>Thermo Scientific</td>
			<td>SV30030.01</td>
			<td>in DPBS with EDTA&#160;</td>
		</tr>
		<tr>
			<td>Phase contrast hemocytometer</td>
			<td>Sigma-Aldrich</td>
			<td>Z359629</td>
			<td>0.1mm deep</td>
		</tr>
		<tr>
			<td>Trypan blue stain</td>
			<td>Gibco</td>
			<td>15250-061</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile 0.9% NaCl injection, USP</td>
			<td>Hospira</td>
			<td>NDC: 0409-4888</td>
			<td>10ml vials</td>
		</tr>
		<tr>
			<td>0.6ml conical polypropylenemi microtubes</td>
			<td>Genesee Scientific</td>
			<td>22-272</td>
			<td></td>
		</tr>
		<tr>
			<td>Atipamezole hydrochloride injection</td>
			<td>Orion Pharma</td>
			<td>NDC: 52483-6298</td>
			<td>5mg/ml solution</td>
		</tr>
		<tr>
			<td>Ketamine hydrochloride injection</td>
			<td>Fort Dodge</td>
			<td>NDC: 0409-2051</td>
			<td>100mg/ml solution</td>
		</tr>
		<tr>
			<td>Dexmedetomidine hydrochloride injection</td>
			<td>Zoetis</td>
			<td>NDC: 54771-2805</td>
			<td>0.5mg/ml solution</td>
		</tr>
		<tr>
			<td>Xylazine hydrochloride injection</td>
			<td>Lloyd</td>
			<td>NDC: 61311-481</td>
			<td>100mg/ml solution</td>
		</tr>
		<tr>
			<td>Carprofen injection</td>
			<td>Pfizer</td>
			<td>NDC: 61106-8501</td>
			<td>50mg/ml solution</td>
		</tr>
		<tr>
			<td>Buprenorphine hydrochloride injection</td>
			<td>Reckitt Benckiser</td>
			<td>NDC: 12496-0757</td>
			<td>0.3mg/ml ampuls</td>
		</tr>
		<tr>
			<td>1ml tuberculin syringes&#160;</td>
			<td>Covidien</td>
			<td>8881501400</td>
			<td></td>
		</tr>
		<tr>
			<td>26G x &#189; (0.45mm x 13mm) syringe needles&#160;</td>
			<td>BD</td>
			<td>305111</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical clippers</td>
			<td>3M</td>
			<td>9661</td>
			<td></td>
		</tr>
		<tr>
			<td>Providone-iodine solution</td>
			<td>Aplicare</td>
			<td>82-217</td>
			<td>NDC: 52380-1905</td>
		</tr>
		<tr>
			<td>Sterile petrolatum ophthalmic ointment&#160;</td>
			<td>Dechra</td>
			<td>NDC: 17033-211</td>
			<td></td>
		</tr>
		<tr>
			<td>70% isopropyl alcohol prep pads</td>
			<td>Kendall</td>
			<td>6818</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile gauze</td>
			<td>Covidien</td>
			<td>8044</td>
			<td>non-woven, 4&#34; x 4&#34;, 4-ply&#160;</td>
		</tr>
		<tr>
			<td>1.7ml conical polypropylene microtubes</td>
			<td>Genesee Scientific</td>
			<td>22-281</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse stereotactic frame</td>
			<td>Stoelting</td>
			<td>51730</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical lamp</td>
			<td>Philips Burton</td>
			<td>CS316W</td>
			<td>Coolspot II Variable Spotlight</td>
		</tr>
		<tr>
			<td>Curved dissecting forceps</td>
			<td>Ted Pella Inc.</td>
			<td>5431</td>
			<td></td>
		</tr>
		<tr>
			<td>Colibri retractors&#160;</td>
			<td>FST</td>
			<td>17000-03</td>
			<td></td>
		</tr>
		<tr>
			<td>Cordless precision power drill</td>
			<td>Dremel&#160;</td>
			<td>1100-01</td>
			<td>Stylus model; 7.2-Volt Lithium-Ion with Docking Station</td>
		</tr>
		<tr>
			<td>Engraving Cutter</td>
			<td>Dremel</td>
			<td>105</td>
			<td>1/32&#34; or 0.8 mm bit diameter</td>
		</tr>
		<tr>
			<td>Microliter syringe</td>
			<td>Hamilton</td>
			<td>75</td>
			<td>Hamilton Microliter&#174; Syringes 700 series; 5&#956;l volume</td>
		</tr>
		<tr>
			<td>Microliter syringe needles</td>
			<td>Hamilton</td>
			<td>7762-06</td>
			<td>33G, small hub RN NDL, 1.5 in, point style 3, 6/PK</td>
		</tr>
		<tr>
			<td>Ethilon 3-0 black monofilament nylon sutures&#160;</td>
			<td>Ethicon</td>
			<td>1663</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic stir bar</td>
			<td>VWR</td>
			<td>74950-296</td>
			<td>7.9mm diameter x 50mm length (5/16&#34; diameter x 2&#34; length)</td>
		</tr>
		<tr>
			<td>1L glass screw-cap storage bottle</td>
			<td>Corning</td>
			<td>1395</td>
			<td>Type 1, Class A borosilicate glass</td>
		</tr>
		<tr>
			<td>Heparin sodium&#160;</td>
			<td>Sagent</td>
			<td>NDC: 25021-400</td>
			<td>1,000U/ml solution</td>
		</tr>
		<tr>
			<td>Peristaltic pump</td>
			<td>Cole Parmer Instruments Group</td>
			<td>77200-60</td>
			<td>Master Flex Easy Load II console drive</td>
		</tr>
		<tr>
			<td>compressed carbogen (95% O2 / 5% CO2)</td>
			<td>available from local vendor</td>
			<td>N/A</td>
			<td>A-type, large cylinder&#160;</td>
		</tr>
		<tr>
			<td>20G x 1 &#189;&#34; aluminum hub blunt needles</td>
			<td>Kendall</td>
			<td>8881202363</td>
			<td>0.9mm x 38.1mm</td>
		</tr>
		<tr>
			<td>Polyurethane ice bucket</td>
			<td>Fisherbrand</td>
			<td>02-591-45</td>
			<td>Capacity: 0.152 oz. (4.5L)</td>
		</tr>
		<tr>
			<td>Collagenase (Type I-S)</td>
			<td>Sigma Aldrich</td>
			<td>C1639</td>
			<td>from Clostridium histolyticum&#160;</td>
		</tr>
		<tr>
			<td>Deoxyribonuclease I</td>
			<td>Worthington Biochemical Corp.</td>
			<td>LS002007</td>
			<td>&#62;2,000 Kunitz units per mg dry weight</td>
		</tr>
		<tr>
			<td>Antistatic polystyrene hexagonal weighing dishes</td>
			<td>Ted Pella Inc.</td>
			<td>20157-3</td>
			<td>top I.D. 115mm, base I.D. 85mm, 203ml volume&#160;</td>
		</tr>
		<tr>
			<td>Stainless steel single edged razor blades&#160;</td>
			<td>Garvey</td>
			<td>40475</td>
			<td></td>
		</tr>
		<tr>
			<td>Bone rongeurs</td>
			<td>FST</td>
			<td>16001-15</td>
			<td></td>
		</tr>
		<tr>
			<td>Hemostat</td>
			<td>FST</td>
			<td>13014-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Large dissection scissors</td>
			<td>Ted Pella Inc.</td>
			<td>1316</td>
			<td></td>
		</tr>
		<tr>
			<td>Small dissection scissors</td>
			<td>FST</td>
			<td>14094-11</td>
			<td></td>
		</tr>
		<tr>
			<td>Blunt end forceps</td>
			<td>Ted Pella Inc.</td>
			<td>13250</td>
			<td></td>
		</tr>
		<tr>
			<td>7ml glass Dounce tissue grinder</td>
			<td>Kontes</td>
			<td>KT885300-0007</td>
			<td></td>
		</tr>
		<tr>
			<td>Percoll Density Centrifugation Media&#160;</td>
			<td>GE Healthcare</td>
			<td>GE17-0891-01</td>
			<td></td>
		</tr>
		<tr>
			<td>10 mL serological pipettes</td>
			<td>Genesee Scientific</td>
			<td>12-104</td>
			<td>single use; sterile</td>
		</tr>
		<tr>
			<td>70&#956;m sterile nylon mesh cell strainers&#160;</td>
			<td>Fisherbrand</td>
			<td>22363548</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor 700-conjugated rat anti-mouse CD45 (clone: 30-F11)</td>
			<td>Biolegend</td>
			<td>103128</td>
			<td></td>
		</tr>
		<tr>
			<td>APC-conjugated mouse anti-mouse NK1.1 (clone: PK136)</td>
			<td>eBiosciences&#160;</td>
			<td>17-5941-82</td>
			<td></td>
		</tr>
		<tr>
			<td>PE-conjugated rat anti-mouse Gr-1 (clone:RB6-8C5)</td>
			<td>BD Pharmigen</td>
			<td>553128</td>
			<td></td>
		</tr>
		<tr>
			<td>PerCP/Cy5.5-conjugated rat anti-mouse CD11b (clone: M1/70)&#160;</td>
			<td>Biolegend</td>
			<td>101228</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor 700-conjugated rat IgG2b, &#954; (clone: RTK4530) isotype control&#160;</td>
			<td>Biolegend</td>
			<td>400628</td>
			<td></td>
		</tr>
		<tr>
			<td>APC-conjugated mouse IgG2a, &#954; (clone: eBM2a) isotype control&#160;</td>
			<td>eBioscience</td>
			<td>17-4724</td>
			<td></td>
		</tr>
		<tr>
			<td>PE-conjugated rat IgG2b, &#954; (clone: eB149/10H5) isotype control&#160;</td>
			<td>eBioscience</td>
			<td>12-4031-82</td>
			<td></td>
		</tr>
		<tr>
			<td>PerCP/Cy5.5-conjugated rat IgG2b, &#954; (clone: RTK4530) isotype control</td>
			<td>Biolegend</td>
			<td>400632</td>
			<td></td>
		</tr>
		<tr>
			<td>Pacific Blue-conjugated mouse anti-mouse granzyme B (Clone: GB11)&#160;</td>
			<td>Biolegend</td>
			<td>515403</td>
			<td></td>
		</tr>
		<tr>
			<td>Pacific Blue-conjugated mouse IgG1, &#954; (Clone: MOPC-21) isotype control&#160;</td>
			<td>Biolegend</td>
			<td>400151</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytofix/Cytoperm</td>
			<td>BD</td>
			<td>554714</td>
			<td></td>
		</tr>
		<tr>
			<td>15ml polypropylene centrifuge tubes</td>
			<td>Genesee Scientific</td>
			<td>21-103</td>
			<td>conical bottom&#160;</td>
		</tr>
		<tr>
			<td>50ml polypropylene centrifuge tubes</td>
			<td>Genesee Scientific</td>
			<td>21-108</td>
			<td>conical bottom</td>
		</tr>
		<tr>
			<td>12x75mm round-bottom polypropylene FACS tubes&#160;</td>
			<td>Fisherbrand</td>
			<td>14-956-1B</td>
			<td></td>
		</tr>
		<tr>
			<td>FACSAria Special Order Research Product flow cytometer/cell sorter</td>
			<td>BD&#160;</td>
			<td>650033</td>
			<td></td>
		</tr>
		<tr>
			<td>Class II Biological Safety Cabinet</td>
			<td>The Baker Company</td>
			<td>SG603</td>
			<td>model: SterilGARD III Advance</td>
		</tr>
	</tbody>
</table>

isolation and flow cytometric analysis of glioma-infiltrating peripheral blood mononuclear cells

Our laboratory has recently demonstrated that natural killer (NK) cells are capable of eradicating orthotopically implanted mouse GL26 and rat CNS-1 malignant gliomas soon after intracranial engraftment if the cancer cells are rendered deficient in their expression of the &#946;-galactoside-binding lectin galectin-1 (gal-1). More recent work now shows that a population of Gr-1+/CD11b+ myeloid cells is critical to this effect. To better understand the mechanisms by which NK and myeloid cells cooperate to confer gal-1-deficient tumor rejection we have developed a comprehensive protocol for the isolation and analysis of glioma-infiltrating peripheral blood mononuclear cells (PBMC). The method is demonstrated here by comparing PBMC infiltration into the tumor microenvironment of gal-1-expressing GL26 gliomas with those rendered gal-1-deficient via shRNA knockdown. The protocol begins with a description of&#160;how to culture and prepare GL26 cells for inoculation into the syngeneic C57BL/6J mouse brain. It then explains the steps involved in the isolation and flow cytometric analysis of glioma-infiltrating PBMCs from the early brain tumor microenvironment. The method is adaptable to a number of in vivo experimental designs in which temporal data on immune infiltration into the brain is required. The method is sensitive and highly reproducible, as glioma-infiltrating PBMCs can be isolated from intracranial tumors as soon as 24 hr post-tumor engraftment with similar cell counts observed from time point matched tumors throughout independent experiments. A single experimentalist can perform the method from brain harvesting to flow cytometric analysis of glioma-infiltrating PBMCs in roughly 4-6 hr depending on the number of samples to be analyzed. Alternative glioma models and/or cell-specific detection antibodies may also be used at the experimentalists&#8217; discretion to assess the infiltration of several other immune cell types of interest without the need for alterations to the overall procedure.

The following gating strategy is used for a typical experiment: FSC-A vs. SSC-A &#8594; SSC-H vs. SSC-W &#8594; FSC-H vs. FSC-W &#8594; CD45 vs. count &#8594; Gr-1 vs. CD11b &#8594; NK1.1 vs. count. Gates placed on Gr-1+/CD11b+ myeloid cells and NK1.1+ NK cells are then stratified based on GzmB expression (Figure 5A). Backgating those cells identified as NK1.1+ NK cells and Gr-1+/CD11b+ myeloid cells in our experiments onto FSC-A vs. SSC-A confirms the smaller lymphoid size of NK cells and the relatively large size of myeloid cells (Figure 5B). Raw data files (i.e., fcs files) are analyzed by commercially available flow cytometric data analysis software such as Flowjo.
A total of 18 C57BL/6J mice were used to demonstrate this method. Nine (9) were engrafted with GL26-Cit-NT and 9 were engrafted with GL26-Cit-gal1i on the same day using equivalent number of cells (3x104). Three mice from each group were euthanized at 24, 48, and 72 hr post-tumor engraftment. The data show that engraftment of GL26-Cit-gal1i glioma cells into the brain of syngeneic C57BL/6J mice rapidly induces the recruitment of CD45+ PBMCs (Figure 6A). Based on the specific antibody cocktail used in the demonstration it can further be shown that Gr-1+/CD11b+ myeloid cells and NK1.1+ NK cells specifically enter the gal-1-deficient tumor microenvironment within 48 hr of tumor engraftment (Figure 6B and 6C); however the total number of glioma-infiltrating myeloid cells far outweighs that of NK cells.
<img alt="Figure 1" src="/files/ftp_upload/53676/53676fig1.jpg" /> 
Figure 1: Preparation of GL26-Cit Cells for Intracranial Engraftment. (A) Representative 10X bright-field and epifluorescence micrographs of GL26-Cit-NT (left images) and GL26-Cit-gal1i (right images) cells grown in culture. (B) Western blot of GL26-Cit-NT (left lane) and GL26-Cit-gal1i (right lane) whole cell lysate. Gamma tubulin (&#947;-tub.) is shown as a loading control. (C) GL26-Cit cell pellet from an approximately 50% confluent T75 tissue culture flask after centrifugation at 550 x g (max RCF) for 5 min&#160;at 4 &#176;C. (D) Bright-field view of a hemocytometer containing GL26-Cit cells (white dots) diluted 1:1 with Trypan Blue to assess cell number and viability. Cells should be &#62;90% viable to ensure reproducible tumor growth. The average of the cell counts from the squares labeled 1 through 5 should be taken to increase the accuracy of cell count estimation. (E) GL26-Cit cells resuspended at 3 x 104 cells/&#956;l&#160;in un-supplemented DMEM for intracranial implantation. <a href="https://www.jove.com/files/ftp_upload/53676/53676fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/53676/53676fig2.jpg" /> 
Figure 2: Stereotactic Engraftment of Glioma Cells into the Striatum of C57BL/6J Mice. (A) Surgical suite layout showing the required surgical instruments and reagents. (B) Close up view of a C57BL/6J mouse harnessed in a stereotactic frame with proper needle placement at +0.5 mm AP, +2.5 mm ML, and -3.0 mm DV relative to bregma. (C) Dorsal view of the mouse skull showing the position of bregma and the target site for tumor cell engraftment. <a href="https://www.jove.com/files/ftp_upload/53676/53676fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" src="/files/ftp_upload/53676/53676fig3.jpg" /> 
Figure 3: Mouse Transcardial Perfusion. (A) Required reagents for dissection, trituration, and enzymatic digestion of mouse brain tissue. (B) Layout of the instruments and reagents required for mouse transcardial perfusion with oxygenated and heparinized Tyrodes&#8217;s solution shown in a laminar flow hood dedicated to terminal mouse surgical procedures. (C) Schematic representation of the heart demonstrating proper instruments and placements required for transcardial perfusion. <a href="https://www.jove.com/files/ftp_upload/53676/53676fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" src="/files/ftp_upload/53676/53676fig4.jpg" /> 
Figure 4: Isolation of Glioma-infiltrating PBMCs. (A) Strategy for the dissection of mouse brain tissue containing early stage orthotopic glioma implants. The top panel demonstrates the sagittal bisection of the ipsilateral hemisphere away from the contralateral hemisphere. The bottom panel demonstrates the two additional coronal cuts necessary to isolate the target tissue containing the tumor implant (highlighted in purple). (B) Single cell brain tissue pellet (white arrow) after enzymatic digestion, filtration through a 70 &#956;m nylon mesh and centrifugation. (C) Properly poured density centrifugation media gradient prior to centrifugation. The white arrow indicates the clean interface formed between the two density centrifugation media layers. (D) Density centrifugation media gradient after centrifugation demonstrating the lipid layer that forms at the top of the 37% density centrifugation media layer white arrow) and the PBMC band (outlined by the dashed black lines) at the interface between the two layers. <a href="https://www.jove.com/files/ftp_upload/53676/53676fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" src="/files/ftp_upload/53676/53676fig5.jpg" /> 
Figure 5: Flow Cytometric Gating Strategy Used to Identify Glioma-infiltrating Gr-1+/CD11b+ Myeloid Cells and NK Cells. (A) Step 1: Total immunolabeled cells isolated from the PBMC band of a density centrifugation media gradient are gated on to exclude cellular debris (FSC-A less than ~50 K). Steps 2 and 3: Doublet discrimination gating to filter out cellular aggregates. Step 4: CD45 gate to identify glioma-infiltrating immune cells. Isotype control is shown as the grey silhouette. Step 5: CD45+ cells stratified based on Gr-1 and CD11b. Isotype control for both Gr-1 and CD11b is overlaid on the plot and enclosed by the gold circle. The red circle indicates Gr-1+/CD11b+ myeloid cells. Step 5&#8217;: Gr-1+/CD11b+ myeloid cells stratified based on GzmB expression. As predicated, these cells do not label with anti-GzmB antibodies over isotype control (grey silhouette). Step 6: Gr-1low cells outlined by the black rectangle in Step 5 stratified based on NK1.1 expression. Isotype control is shown as the grey silhouette. Step 6&#8217;: NK1.1high cells stratified based on GzmB expression. These cells indeed label with anti-GzmB antibodies above isotype control (grey silhouette). (B) Backgating of Gr-1+/CD11b+ myeloid cells onto FSC-A vs. SSC-A demonstrating that NK cells have a smaller lymphoid size as compared to the larger sized Gr-1+/CD11b+ myeloid cells. <a href="https://www.jove.com/files/ftp_upload/53676/53676fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" src="/files/ftp_upload/53676/53676fig6.jpg" /> 
Figure 6: Comparison of PBMC Infiltration into the GL26-Cit-NT vs. GL26-Cit-gal1i Tumor Microenvironment over the First Three Days of Intracranial Tumor Growth. (A) Total CD45+ immune cells. (B) CD45+/Gr-1+/CD11b+ myeloid cells. (C) CD45+/NK1.1+ NK cells. Data points from PBMCs isolated from GL26-Cit-gal1i gliomas are connected by smooth lines, whiles those isolated from GL26-Cit-NT gliomas are connected by dashed lines. Glioma-infiltrating PBMCs from three mice were analyzed per tumor type at each time point. Numbers associated with each data point on the GL26-Cit-gal1i curves represent the fold-induction of that particular PBMC type over GL26-Cit-NT at the specified hour post-tumor implantation (HPI). Data represent the mean number of immune cells counted &#177; the standard error of the mean (SEM). Statistical analysis was performed by 2-way analysis of variance. <a href="https://www.jove.com/files/ftp_upload/53676/53676fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Isolation and Flow Cytometric Analysis of Glioma-infiltrating Peripheral Blood Mononuclear Cells at JoVE.com

Isolation and Flow Cytometric Analysis of Glioma-infiltrating Peripheral Blood Mononuclear Cells

Presented here is a straightforward method for the isolation and flow cytometric analysis of glioma-infiltrating peripheral blood mononuclear cells that yields time-dependent quantitative data on the number and activation status of immune cells entering the early brain tumor microenvironment.

Our laboratory has recently demonstrated that natural killer (NK) cells are capable of eradicating orthotopically implanted mouse GL26 and rat CNS-1 ...

isolation-flow-cytometric-analysis-glioma-infiltrating-peripheral

Nanyang Technological University

Research

JoVE Journal

Immunology and Infection

15.7K Views.  University of Michigan. Presented here is a straightforward method for the isolation and flow cytometric analysis of glioma-infiltrating peripheral blood mononuclear cells that yields time-dependent quantitative data on the number and activation status of immune cells entering the early brain tumor microenvironment.

Video: Isolation and Flow Cytometric Analysis of Glioma-infiltrating Peripheral Blood Mononuclear Cells

Isolation of Mouse Peritoneal Cavity Cells

The peritoneal cavity is a membrane-bound and fluid-filled abdominal cavity of mammals, which contains the liver, spleen, most of the gastro-intestinal tract and other viscera. It harbors a number of immune cells including macrophages, B cells and T cells. The presence of a high number of na&iuml;ve macrophages in the peritoneal cavity makes it a preferred site for the collection of na&iuml;ve tissue resident macrophages (1). The peritoneal cavity is also important to the study of B cells because of the presence of a unique peritoneal cavity-resident B cell subset known as B1 cells in addition to conventional B2 cells. B1 cells are subdivided into B1a and B1b cells, which can be distinguished by the surface expression of CD11b and CD5. B1 cells are an important source of natural IgM providing early protection from a variety of pathogens (2-4). These cells are autoreactive in nature (5), but how they are controlled to prevent autoimmunity is still not understood completely. On the contrary, CD5+ B1a cells possess some regulatory properties by virtue of their IL-10 producing capacity (6). Therefore, peritoneal cavity B1 cells are an interesting cell population to study because of their diverse function and many unaddressed questions associated with their development and regulation. The isolation of peritoneal cavity resident immune cells is tricky because of the lack of a defined structure inside the peritoneal cavity. Our protocol will describe a procedure for obtaining viable immune cells from the peritoneal cavity of mice, which then can be used for phenotypic analysis by flow cytometry and for different biochemical and immunological assays.

The peritoneal cavity in mammals contains different immune cell populations crucial for innate immune responses. An efficient isolation method is required for biochemical and functional analyses of these cells. Here we provide a comprehensive method for the isolation of peritoneal cavity cells in the mouse.

The peritoneal cavity is a membrane-bound and fluid-filled abdominal cavity of mammals, which contains the liver, spleen, most of the gastro-intestinal ...

Induction of Alloantigen-specific Anergy in Human Peripheral Blood Mononuclear Cells by Alloantigen Stimulation with Co-stimulatory Signal Blockade

Allogeneic hematopoietic stem cell transplantation (AHSCT) offers the best chance of cure for many patients with congenital and acquired hematologic diseases. Unfortunately, transplantation of alloreactive donor T cells which recognize and damage healthy patient tissues can result in Graft-versus-Host Disease (GvHD)1. One challenge to successful AHSCT is the prevention of GvHD without associated impairment of the beneficial effects of donor T cells, particularly immune reconstitution and prevention of relapse. GvHD can be prevented by non-specific depletion of donor T cells from stem cell grafts or by administration of pharmacological immunosuppression. Unfortunately these approaches increase infection and disease relapse2-4. An alternative strategy is to selectively deplete alloreactive donor T cells after allostimulation by recipient antigen presenting cells (APC) before transplant. Early clinical trials of these allodepletion strategies improved immune reconstitution after HLA-mismatched HSCT without excess GvHD5, 6. However, some allodepletion techniques require specialized recipient APC production6, 7and some approaches may have off-target effects including depletion of donor pathogen-specific T cells8and CD4 T regulatory cells9.One alternative approach is the inactivation of alloreactive donor T cells via induction of alloantigen-specific hyporesponsiveness. This is achieved by stimulating donor cells with recipient APC while providing blockade of CD28-mediated co-stimulation signals10.This "alloanergization" approach reduces alloreactivity by 1-2 logs while preserving pathogen- and tumor-associated antigen T cell responses in vitro11. The strategy has been successfully employed in 2 completed and 1 ongoing clinical pilot studies in which alloanergized donor T cells were infused during or after HLA-mismatched HSCT resulting in rapid immune reconstitution, few infections and less severe acute and chronic GvHD than historical control recipients of unmanipulated HLA-mismatched transplantation12. Here we describe our current protocol for the generation of peripheral blood mononuclear cells (PBMC) which have been alloanergized to HLA-mismatched unrelated stimulator PBMC. Alloanergization is achieved by allostimulation in the presence of monoclonal antibodies to the ligands B7.1 and B7.1 to block CD28-mediated costimulation. This technique does not require the production of specialized stimulator APC and is simple to perform, requiring only a single and relatively brief ex vivo incubation step. As such, the approach can be easily standardized for clinical use to generate donor T cells with reduced alloreactivity but retaining pathogen-specific immunity for adoptive transfer in the setting of AHSCT to improve immune reconstitution without excessive GvHD.

This paper describes a simple technique to induce alloantigen-specific anergy in human peripheral blood mononuclear cells. The technique can be applied clinically to generate non-alloreactive donor cells. Infusion of these cells could improve immune reconstitution and reduce toxicity after allogeneic hematopoietic stem cell transplantation.

Allogeneic hematopoietic stem cell transplantation (AHSCT) offers the best chance of cure for many patients with congenital and acquired hematologic ...

Flow Cytometric Isolation of Primary Murine Type II Alveolar Epithelial Cells for Functional and Molecular Studies

Throughout the last years, the contribution of alveolar type II epithelial cells (AECII) to various aspects of immune regulation in the lung has been increasingly recognized. AECII have been shown to participate in cytokine production in inflamed airways and to even act as antigen-presenting cells in both infection and T-cell mediated autoimmunity 1-8. Therefore, they are especially interesting also in clinical contexts such as airway hyper-reactivity to foreign and self-antigens as well as infections that directly or indirectly target AECII. However, our understanding of the detailed immunologic functions served by alveolar type II epithelial cells in the healthy lung as well as in inflammation remains fragmentary. Many studies regarding AECII function are performed using mouse or human alveolar epithelial cell lines 9-12. Working with cell lines certainly offers a range of benefits, such as the availability of large numbers of cells for extensive analyses. However, we believe the use of primary murine AECII allows a better understanding of the role of this cell type in complex processes like infection or autoimmune inflammation. Primary murine AECII can be isolated directly from animals suffering from such respiratory conditions, meaning they have been subject to all additional extrinsic factors playing a role in the analyzed setting. As an example, viable AECII can be isolated from mice intranasally infected with influenza A virus, which primarily targets these cells for replication 13. Importantly, through ex vivo infection of AECII isolated from healthy mice, studies of the cellular responses mounted upon infection can be further extended.
Our protocol for the isolation of primary murine AECII is based on enzymatic digestion of the mouse lung followed by labeling of the resulting cell suspension with antibodies specific for CD11c, CD11b, F4/80, CD19, CD45 and CD16/CD32. Granular AECII are then identified as the unlabeled and sideward scatter high (SSChigh) cell population and are separated by fluorescence activated cell sorting 3.
In comparison to alternative methods of isolating primary epithelial cells from mouse lungs, our protocol for flow cytometric isolation of AECII by negative selection yields untouched, highly viable and pure AECII in relatively short time. Additionally, and in contrast to conventional methods of isolation by panning and depletion of lymphocytes via binding of antibody-coupled magnetic beads 14, 15, flow cytometric cell-sorting allows discrimination by means of cell size and granularity. Given that instrumentation for flow cytometric cell sorting is available, the described procedure can be applied at relatively low costs. Next to standard antibodies and enzymes for lung disintegration, no additional reagents such as magnetic beads are required. The isolated cells are suitable for a wide range of functional and molecular studies, which include in vitro culture and T-cell stimulation assays as well as transcriptome, proteome or secretome analyses 3, 4.

We describe the rapid isolation of primary murine type II alveolar epithelial cells (AECII) by flow cytometric negative selection. These AECII show high viability and purity and are suitable for a wide range of functional and molecular studies regarding their role in respiratory conditions such as autoimmune or infectious diseases.

Throughout  the last years, the contribution of alveolar type II epithelial cells (AECII)  to various aspects of immune regulation in the lung has been ...

Detecting Glycogen in Peripheral Blood Mononuclear Cells with Periodic Acid Schiff Staining

Periodic acid Schiff (PAS) staining is an immunohistochemical technique used on muscle biopsies and as a diagnostic tool for blood samples. Polysaccharides such as glycogen, glycoproteins, and glycolipids stain bright magenta making it easy to enumerate positive and negative cells within the tissue. In muscle cells PAS staining is used to determine the glycogen content in different types of muscle cells, while in blood cell samples PAS staining has been explored as a diagnostic tool for a variety of conditions. Blood contains a proportion of white blood cells that belong to the immune system. The notion that cells of the immune system possess glycogen and use it as an energy source has not been widely explored. Here, we describe an adapted version of the PAS staining protocol that can be applied on peripheral blood mononuclear immune cells from human venous blood. Small cells with PAS-positive granules and larger cells with diffuse PAS staining were observed. Treatment of samples with amylase abrogates these patterns confirming the specificity of the stain. An alternate technique based on enzymatic digestion confirmed the presence and amount of glycogen in the samples. This protocol is useful for hematologists or immunologists studying polysaccharide content in blood-derived lymphocytes.

Periodic acid Schiff staining is a technique that visualizes the polysaccharide content of tissues. This article demonstrates periodic acid Schiff staining protocol adapted for use on peripheral blood mononuclear cells purified from human venous blood. Such samples are enriched for lymphocytes and other white blood cells of the immune system.

Periodic acid Schiff (PAS) staining is an immunohistochemical technique used on muscle biopsies and as a diagnostic tool for blood samples. ...

Isolation and Flow Cytometric Analysis of Immune Cells from the Ischemic Mouse Brain

Ischemic stroke initiates a robust inflammatory response that starts in the intravascular compartment and involves rapid activation of brain resident cells. A key mechanism of this inflammatory response is the migration of circulating immune cells to the ischemic brain facilitated by chemokine release and increased endothelial adhesion molecule expression. Brain-invading leukocytes are well-known contributing to early-stage secondary ischemic injury, but their significance for the termination of inflammation and later brain repair has only recently been noticed.
Here, a simple protocol for the efficient isolation of immune cells from the ischemic mouse brain is provided. After transcardial perfusion, brain hemispheres are dissected and mechanically dissociated. Enzymatic digestion with Liberase&#160;is followed by density gradient (such as Percoll) centrifugation to remove myelin and cell debris. One major advantage of this protocol is the single-layer density gradient procedure which does not require time-consuming preparation of gradients and can be reliably performed. The approach yields highly reproducible cell counts per brain hemisphere and allows for measuring several flow cytometry panels in one biological replicate. Phenotypic characterization and quantification of brain-invading leukocytes after experimental stroke may contribute to a better understanding of their multifaceted roles in ischemic injury and repair.

Inflammation plays a central role in the pathogenesis of ischemic stroke. Increasing evidence suggests that it acts as a double-edged sword which exacerbates early brain injury, but also contributes to later repair. This protocol describes the isolation of immune cells from the ischemic brain and their subsequent flow cytometric phenotyping.

Ischemic stroke initiates a robust inflammatory response that starts in the intravascular compartment and involves rapid activation of brain resident ...

Isolation and Flow Cytometric Characterization of Murine Small Intestinal Lymphocytes

The intestines &#8212; which contain the largest number of immune cells of any organ in the body &#8212; are constantly exposed to foreign antigens, both microbial and dietary. Given an increasing understanding that these luminal antigens help shape the immune response and that education of immune cells within the intestine is critical for a number of systemic diseases, there has been increased interest in characterizing the intestinal immune system. However, many published protocols are arduous and time-consuming. We present here a simplified protocol for the isolation of lymphocytes from the small-intestinal lamina propria, intraepithelial layer, and Peyer&#39;s patches that is rapid, reproducible, and does not require laborious Percoll gradients. Although the protocol focuses on the small intestine, it is also suitable for analysis of the colon. Moreover, we highlight some aspects that may need additional optimization depending on the specific scientific question. This approach results in the isolation of large numbers of viable lymphocytes that can subsequently be used for flow cytometric analysis or alternate means of characterization.

There is growing interest in the quantitative characterization of intestinal lymphocytes owing to increasing recognition that these cells play a critical role in a variety of intestinal and systemic diseases. In this protocol, we describe how to isolate single cell populations from different small-intestinal compartments for subsequent flow cytometric characterization.

The intestines &#8212; which contain the largest number of immune cells of any organ in the body &#8212; are constantly exposed to foreign antigens, both ...

Flow Cytometric Analysis of Particle-bound Bet v 1 Allergen in PM10

Flow cytometry is a method widely used to quantify suspended solids such as cells or bacteria in a size range from 0.5 to several tens of micrometers in diameter. In addition to a characterization of forward and sideward scatter properties, it enables the use of fluorescent labeled markers like antibodies to detect respective structures. Using indirect antibody staining, flow cytometry is employed here to quantify birch pollen allergen (precisely Bet v 1)-loaded particles of 0.5 to 10 &#181;m in diameter in inhalable particulate matter (PM10, particle size &#8804;10 &#181;m in diameter). PM10 particles may act as carriers of adsorbed allergens possibly transporting them to the lower respiratory tract, where they could trigger allergic reactions.
So far the allergen content of PM10 has been studied by means of enzyme linked immunosorbent assays (ELISAs) and scanning electron microscopy. ELISA measures the dissolved and not the particle-bound allergen. Compared to scanning electron microscopy, which can visualize allergen-loaded particles, flow cytometry may additionally quantify them. As allergen content of ambient air can deviate from birch pollen count, allergic symptoms might perhaps correlate better with allergen exposure than with pollen count. In conjunction with clinical data, the presented method offers the opportunity to test in future experiments whether allergic reactions to birch pollen antigens are associated with the Bet v 1 allergen content of PM10 particles &#62;0.5 &#181;m.

Here, we present a protocol to quantify allergen-loaded particles by flow cytometry. Ambient particulate matter particles may act as carriers of adsorbed allergens. We show here that flow cytometry, a method widely used to characterize suspended solids &#62;0.5 &#181;m in diameter, can be used to measure these allergen-loaded particles.

Flow cytometry is a method widely used to quantify suspended solids such as cells or bacteria in a size range from 0.5 to several tens of micrometers in ...

Flow Cytometric Analysis of Natural Killer Cell Lytic Activity in Human Whole Blood

NK cell cytotoxicity is a widely used measure to determine the effect of outside intervention on NK cell function. However, the accuracy and reproducibility of this assay can be considered unstable, either because of user&#39;s errors or because of the sensitivity of NK cells to experimental manipulation. To eliminate these issues, a workflow that reduces them to a minimum was established and is presented here. To illustrate, we obtained blood samples, at various time points, from runners (n = 4) that were submitted to an intense bout of exercise. First, NK cells are simultaneously identified and isolated through CD56 tagging and magnetic-based sorting, directly from whole blood and from as little as one milliliter. The sorted NK cells are removed of any reagent or capping antibodies. They can be counted in order to establish an accurate NK cell count per milliliter of blood. Secondly, the sorted NK cells (effectors cells or E) can be mixed with 3,3&#39;-Diotadecyloxacarbocyanine Perchlorate (DiO) tagged K562 cells (target cells or T) at an assay-optimal 1:5 T:E ratio, and analyzed using an imaging flow-cytometer that allows for the visualization of each event and the elimination of any false positive or false negatives (such as doublets or effector cells). This workflow can be completed in about 4 h, and allows for very stable results even when working with human samples. When available, research teams can test several experimental interventions in human subjects, and compare measurements across several time points without compromising the data&#39;s integrity.

This work describes an advanced workflow for the accurate and fast determination of NK (Natural Killer) cell count and NK cell cytotoxicity in human blood samples.

NK cell cytotoxicity is a widely used measure to determine the effect of outside intervention on NK cell function. However, the accuracy and ...

Isolation and Flow Cytometric Analysis of Human Endocervical Gamma Delta T Cells

The female reproductive tract (FRT) mucosal immune system serves as the first line of defense. Better knowledge of the genital mucosa is therefore essential for understanding pathogenicity of different pathogens including HIV. Gamma delta (GD) T cells are the prototype of &#39;unconventional&#39; T cells and represent a relatively small subset of T cells defined by their expression of heterodimeric T-cell receptors (TCRs) composed of gamma and delta chains. This sets them apart from the classical and much better known CD4+ helper T cells and CD8+ cytotoxic T cells that are defined by alpha-beta TCRs. GD T cells often show tissue-specific localization and are enriched in epithelium. GD T cells orchestrate immune responses in inflammation, tumor surveillance, infectious disease, and autoimmunity.
Here, we present a method to reproducibly isolate and analyze human endocervical intraepithelial GD T lymphocytes. We have used endocervical cytobrush samples from women participating in the Women&#39;s Interagency HIV Infection Study (WIHS). Knowledge about GD T cells interactions during conditions in which there is an insult to the vaginal mucosal could be applied to any clinical study in which mucosal vulnerability is addressed, including the development of vaginal microbicides.In addition, knowledge about mucosal GD T cell responses has potential for application of GD T cell-based immune therapy in treating infectious diseases.

We describe here an isolation method to obtain human endocervical intraepithelial lymphocytes for the analysis of intraepithelial gamma delta T cells. This protocol can be extended for the purification of endocervical gamma delta T cells by magnetic beads or by cell sorting.

The female reproductive tract (FRT) mucosal immune system serves as the first line of defense. Better knowledge of the genital mucosa is therefore ...

Digestion of the Murine Liver for a Flow Cytometric Analysis of Lymphatic Endothelial Cells

Within the liver, lymphatic vessels are found within the portal triad, and their described function is to remove interstitial fluid from the liver to the lymph nodes where cellular debris and antigens can be surveyed. We are very interested in understanding how the lymphatic vasculature might be involved in inflammation and immune cell function within the liver. However, very little has been published establishing digestion protocols for the isolation of lymphatic endothelial cells (LECs) from the liver or specific markers that can be used to evaluate liver LECs on a per cell basis. Therefore, we optimized a method for the digestion and staining of the liver in order to evaluate the LEC population in the liver. We are confident that the method outlined here will be useful for the identification and isolation of LECs from the liver and will strengthen our understanding of how LECs respond to the liver microenvironment.

The goal of this protocol is to identify lymphatic endothelial cell populations within the liver using described markers. We utilize collagenase IV and DNase and a gentle mincing of tissue, combined with flow cytometry, to identify a distinct population of lymphatic endothelial cells.

Within the liver, lymphatic vessels are found within the portal triad, and their described function is to remove interstitial fluid from the liver to the ...