We thank Paolo Dellabona and Giulia Casorati for scientific support and critical reading of the manuscript. We also thank the NIH Tetramer Core Facility for mouse CD1d tetramer. The study was funded by Fondazione Cariplo Grant 2018-0366 (to M.F.) and Italian Association for Cancer Research (AIRC) fellowship 2019-22604 (to G.D.).

Procedures described here were reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) (no. 1048) at the San Raffaele Scientific Institute.
NOTE: All the procedures must be performed under sterile conditions. All the reagents used are listed in the Table of Materials.
1. Spleen processing
<ol>
	<li>Euthanize iV&#945;14-J&#945;18 mice by inhalation of CO2 according to the institutional policy. 
	NOTE: iV&#945;14-J&#945;18 mice must be 8 weeks old or older. To avoid rejection of the cells from the in vivo transfer of the cells, consider that cells isolated from female mice can be adoptively transferred both in male and female recipients, whereas cells isolated from male mice can be transferred only in male recipients. For in vitro experiments, no gender bias must be considered. More mice can be pooled in order to obtain more cells.</li>
	<li>Dissect the mouse spleen and smash it through a 70 nm cell strainer to obtain a single-cell suspension in 10 mL of phosphate buffered saline (PBS) with 2% fetal bovine serum (FBS).</li>
	<li>Centrifuge at 300 x g for 5 min.</li>
	<li>Remove the supernatant by inversion and process with erythrocyte lysis buffer. Resuspend the cell pellet with 1 mL of sterile ACK (Ammonium-Chloride-Potassium) Lysing Buffer, incubate for 3 min at room temperature, and block with 5 mL of PBS with 2% FBS. Centrifuge at 300 x g for 5 min. 
	NOTE: ACK is commercially available; it consists of a solution of 0.15 M NH4Cl, 10 mM KHCO3, and 0.1 mM Na2EDTA (ethylenediaminetetraacetic acid) dissolved in bidistilled H2O, pH 7.2-7.4. If homemade, sterilize by filtration with a 0.22 &#181;m filter.</li>
	<li>Remove the supernatant by inversion. Resuspend the cell pellet in 3 mL of PBS with 2% FBS and remove fat residues by pipetting. If needed, pool the cells coming from different mice.</li>
	<li>Count the cells and keep 50 &#181;L for FACS analysis.</li>
</ol>
2. T cell enrichment
NOTE: For the enrichment steps, work fast, keep the cells cold and use solutions pre-cooled at 4 &#176;C overnight and then kept on ice
<ol>
	<li>Centrifuge at 300 x g for 5 min.</li>
	<li>Resuspend all the cells in the appropriate amount of PBS with 2% FBS (500 &#181;L for 107 cells) and Fc blocker (2.5 &#181;L x 107 cells); incubate for 15 min at room temperature (RT).</li>
	<li>Wash with 1-2 mL of MACS separation buffer (MB) per 107 total cells and centrifuge at 300 x g for 10 min. 
	NOTE: MACS buffer is commercially available. It consists of PBS pH 7.2, 0.5% bovine serum albumin (BSA), and 2 mM EDTA. If homemade, sterilize by filtration with a 0.22 &#181;m filter.</li>
	<li>Remove the supernatant by inversion and stain the cells with CD19-FITC and H2(IAb)-FITC (use 5 &#181;L x 107 cells in 100 &#181;L of MB). Mix well and incubate for 15 min in the dark at 4-8 &#176;C.</li>
	<li>Wash cells by adding 1&#8722;2 mL of MB per 107 cells and centrifuge at 300 x g for 10 min.</li>
	<li>Pipette off the supernatant completely and resuspend the cell pellet in 90 &#181;L of MB per 107 total cells. Add 10 &#181;L of Anti-FITC MicroBeads per 107 total cells. Mix well and incubate for 15 min in the dark at 4-8 &#176;C.</li>
	<li>Wash the cells by adding 1&#8722;2 mL of MB per 107 cells and centrifuge at 300 x g for 10 min.</li>
	<li>Pipette off the supernatant completely and resuspend up to 1.25 x 108 cell in 500 &#181;L of MB.</li>
	<li>Place a LD column in the magnetic field of the MACS separator to proceed to the depletion. To avoid clogging, apply a pre-separation filter on the LD column and rinse with 2 mL of MB.</li>
	<li>When the column reservoir is empty, apply the cell suspension onto the filter. Collect the unlabeled cells that pass through the column.</li>
	<li>Wash 3 times with 1 mL of MB, only when the column reservoir is empty. Collect the total effluent, which will be enriched in T cells, and count the cells. Always keep 50 &#181;L for FACS analysis.</li>
</ol>
3. iNKT cell enrichment
<ol>
	<li>Centrifuge at 300 x g for 5 min and remove the supernatant by inversion.</li>
	<li>Stain the cells with CD1d-tetramer-PE (mouse PBS57-CD1d-tetramer), according to the antibody titration in 50 &#181;L of MB per 106 cells. Mix well and incubate for 30 min in the dark on ice. 
	NOTE: The procedure can also be performed with APC-labelled mCD1d tetramers and anti-APC beads; adjusting the fluorochromes used in the following staining accordingly. In the present protocol we used mouse PBS-57-CD1d-tetramers provided by NIH. &#945;galactosylceramide (&#945;Gal-Cer) is the prototypical antigen recognized by iNKT cells; PBS-57 is an analogue of &#945;Gal-Cer with improved solubility9; the NIH Tetramer Facility provides PBS-57 ligand complexed to CD1d tetramers. However, other CD1d dimers/tetramers/dextramers are commercially available and can be loaded with a lipidic antigen as &#945;Gal-Cer. We envisage the possibility to adjust the protocol for their use.</li>
	<li>Wash the cells by adding 1&#8722;2 mL of MB per 107 cells and centrifuge at 300 x g for 10 min.</li>
	<li>Pipette off the supernatant completely and resuspend the cell pellet in 80 &#181;L of MB per 107 total cells. Add 20 &#181;L of Anti-PE MicroBeads per 107 total cells. Mix well and incubate for 15 min in the dark at 4-8 &#176;C.</li>
	<li>Wash cells by adding 1&#8722;2 mL of MB per 107 cells and centrifuge at 300 x g for 10 min.</li>
	<li>Pipette off the supernatant completely and resuspend up to 108 cells in 500 &#181;L of MB. Otherwise if cells exceed 108, adjust the volume accordingly.</li>
	<li>According to the cell count, place a LS (up to 108) or MS (up to 107) column in the magnetic field of the MACS separator. Rinse the column with MB (3 mL for LS, 500 &#181;L for MS).</li>
	<li>Apply the cell suspension onto the column.</li>
	<li>Collect unlabeled cells that pass through. Wash the column 3 times by adding the appropriate amount of MB (3 x 3 mL for LS column, 3 x 500 &#181;L for MS column) only when the column reservoir is empty. The total effluent is the negative fraction.</li>
	<li>Remove the column from the magnetic field and place it on a new collection tube.</li>
	<li>Pipette MB onto the column (5 mL for LS column or 1 mL for MS column); push the provided plunger into the column and flush out the positive fraction (enriched in iNKT cells).</li>
	<li>To further increase the iNKT cell recovery, centrifuge the negative fraction at 300 x g for 10 min and repeat steps 3.6-3.7 with a new LS or MS column. Pool the positive fractions and determine cell count. Keep 50 &#181;L of both positive and negative fractions for FACS analysis.</li>
	<li>Check the Purification steps by FACS analysis. Samples include: spleen ex-vivo, T cell enriched fraction, iNKT positive fraction and iNKT negative fraction. Stain the cells with: CD19-FITC, IAb-FITC, CD1d-tetramer-PE, TCR&#946;-APC and DAPI. 
	NOTE: The expected recovery from one iV&#945;14-J&#945;18 mouse is 2x106 iNKT cells .</li>
</ol>
4. iNKT cell activation and expansion
<ol>
	<li>Activate purified iNKT cells with mouse T activator anti-CD3/CD28 magnetic beads in a 1:1 ratio.
	<ol>
		<li>Centrifuge the iNKT cell positive fraction at 300 x g for 5 min.</li>
		<li>Meanwhile transfer the appropriate volume of anti-CD3/CD28 magnetic beads to a tube and add an equal volume of PBS, vortex for 5 seconds. Place the tube on a magnet for 1 minute and discard the supernatant.</li>
		<li>Remove the tube from the magnet and resuspend the washed magnetic beads in the proper volume of complete RPMI (RPMI 1640 medium, 10% heat-inactivated FCS, 1 mM sodium pyruvate, 1% Non-essential amino acids, 10 U/ml penicyllin and streptomycin, 50 &#956;M &#946;-Mercaptoethanol) to have 5 x 105 iNKT cells in 1 mL. Use this suspension to resuspend the centrifuged iNKT positive fraction.</li>
	</ol>
	</li>
	<li>Plate 1 mL of the cell suspension (5 x 105 iNKT cells) and anti-CD3/CD28 magnetic beads in a 48 well plate with 20 U/mL IL-2 and incubate at 37 &#176;C.</li>
	<li>After 5 days, add 10 ng/mL IL-7.</li>
	<li>Split the cells 1:2 when they reach 80-90% confluence, always add 20U/mL IL-2 and 10 ng/mL IL-7. In these conditions, iNKT cells can be expanded for up to 15 days.</li>
</ol>

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<li>Cortesi, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Bimodal+CD40%2FFas-Dependent+Crosstalk+between+iNKT+Cells+and+Tumor-Associated+Macrophages+Impairs+Prostate+Cancer+Progression%5BTitle%5D)+AND+%22Cell+Reports%22%5BJournal%5D)">Bimodal CD40/Fas-Dependent Crosstalk between iNKT Cells and Tumor-Associated Macrophages Impairs Prostate Cancer Progression.</a> Cell Reports. 22 (11), 3006-3020 (2018).</li>
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<li>Crowe, N. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Differential+antitumor+immunity+mediated+by+NKT+cell+subsets+in+vivo%5BTitle%5D)+AND+%22Journal+of+Experimental+Medicine%22%5BJournal%5D)">Differential antitumor immunity mediated by NKT cell subsets in vivo.</a> Journal of Experimental Medicine. 202 (9), 1279-1288 (2005).</li>
<li>de Lalla, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Production+of+profibrotic+cytokines+by+invariant+NKT+cells+characterizes+cirrhosis+progression+in+chronic+viral+hepatitis%5BTitle%5D)+AND+%22Journal+of+Immunology%22%5BJournal%5D)">Production of profibrotic cytokines by invariant NKT cells characterizes cirrhosis progression in chronic viral hepatitis.</a> Journal of Immunology. 173 (2), 1417-1425 (2004).</li>
<li>Tian, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((CD62L%2B+NKT+cells+have+prolonged+persistence+and+antitumor+activity+in+vivo%5BTitle%5D)+AND+%22Journal+of+Clinical+Investigation%22%5BJournal%5D)">CD62L+ NKT cells have prolonged persistence and antitumor activity in vivo.</a> Journal of Clinical Investigation. 126 (6), 2341-2355 (2016).</li>
<li>Gaya, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Initiation+of+Antiviral+B+Cell+Immunity+Relies+on+Innate+Signals+from+Spatially+Positioned+NKT+Cells%5BTitle%5D)+AND+%22Cell%22%5BJournal%5D)">Initiation of Antiviral B Cell Immunity Relies on Innate Signals from Spatially Positioned NKT Cells.</a> Cell. 172 (3), 517-533 (2018).</li>
<li>Rotolo, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Enhanced+Anti-lymphoma+Activity+of+CAR19-iNKT+Cells+Underpinned+by+Dual+CD19+and+CD1d+Targeting%5BTitle%5D)+AND+%22Cancer+Cell%22%5BJournal%5D)">Enhanced Anti-lymphoma Activity of CAR19-iNKT Cells Underpinned by Dual CD19 and CD1d Targeting.</a> Cancer Cell. 34 (4), 596-610 (2018).</li>
<li>Schneidawind, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Third-party+CD4%2B+invariant+natural+killer+T+cells+protect+from+murine+GVHD+lethality%5BTitle%5D)+AND+%22Blood%22%5BJournal%5D)">Third-party CD4+ invariant natural killer T cells protect from murine GVHD lethality.</a> Blood. 125 (22), 3491-3500 (2015).</li>
<li>Schneidawind, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((CD4%2B+invariant+natural+killer+T+cells+protect+from+murine+GVHD+lethality+through+expansion+of+donor+CD4%2BCD25%2BFoxP3%2B+regulatory+T+cells%5BTitle%5D)+AND+%22Blood%22%5BJournal%5D)">CD4+ invariant natural killer T cells protect from murine GVHD lethality through expansion of donor CD4+CD25+FoxP3+ regulatory T cells.</a> Blood. 124 (22), 3320-3328 (2014).</li>
<li>Schneidawind, D., Pierini, A., Negrin, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Regulatory+T+cells+and+natural+killer+T+cells+for+modulation+of+GVHD+following+allogeneic+hematopoietic+cell+transplantation%5BTitle%5D)+AND+%22Blood%22%5BJournal%5D)">Regulatory T cells and natural killer T cells for modulation of GVHD following allogeneic hematopoietic cell transplantation.</a> Blood. 122 (18), 3116-3121 (2013).</li>
<li>Leveson-Gower, D. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Low+doses+of+natural+killer+T+cells+provide+protection+from+acute+graft-versus-host+disease+via+an+IL-4-dependent+mechanism%5BTitle%5D)+AND+%22Blood%22%5BJournal%5D)">Low doses of natural killer T cells provide protection from acute graft-versus-host disease via an IL-4-dependent mechanism.</a> Blood. 117 (11), 3220-3229 (2011).</li>
<li>Coman, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Human+CD4-+invariant+NKT+lymphocytes+regulate+graft+versus+host+disease%5BTitle%5D)+AND+%22Oncoimmunology%22%5BJournal%5D)">Human CD4- invariant NKT lymphocytes regulate graft versus host disease.</a> Oncoimmunology. 7 (11), 1470735(2018).</li>
<li>Xu, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((NKT+Cells+Coexpressing+a+GD2-Specific+Chimeric+Antigen+Receptor+and+IL15+Show+Enhanced+In+vivo+Persistence+and+Antitumor+Activity+against+Neuroblastoma%5BTitle%5D)+AND+%22Clinical+Cancer+Research%22%5BJournal%5D)">NKT Cells Coexpressing a GD2-Specific Chimeric Antigen Receptor and IL15 Show Enhanced In vivo Persistence and Antitumor Activity against Neuroblastoma.</a> Clinical Cancer Research. 25 (23), 7126-7138 (2019).</li>
<li>Heczey, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Anti-GD2+CAR-NKT+cells+in+patients+with+relapsed+or+refractory+neuroblastoma%3A+an+interim+analysis%5BTitle%5D)+AND+%22Nature+Medicine%22%5BJournal%5D)">Anti-GD2 CAR-NKT cells in patients with relapsed or refractory neuroblastoma: an interim analysis.</a> Nature Medicine. 26 (11), 1686-1690 (2020).</li>
<li>Exley, M. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Adoptive+Transfer+of+Invariant+NKT+Cells+as+Immunotherapy+for+Advanced+Melanoma%3A+A+Phase+I+Clinical+Trial%5BTitle%5D)+AND+%22Clinical+Cancer+Research%22%5BJournal%5D)">Adoptive Transfer of Invariant NKT Cells as Immunotherapy for Advanced Melanoma: A Phase I Clinical Trial.</a> Clinical Cancer Research. 23 (14), 3510-3519 (2017).</li>
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</ol>

The authors have nothing to disclose.

Here we show a reproducible and feasible protocol to obtain millions of ready-to-use iNKT cells. Due to the paucity of these cells in vivo, a method to expand them was highly needed. The protocol we propose requires neither a particular instrumentation nor a high number of mice. We exploited iV&#945;14-J&#945;18 transgenic mice on purpose to reduce the number of mice needed for the procedure.
Another successful protocol for iNKT cell expansion from iV&#945;14-J&#945;18 transgenic mice is avail...

Invariant Natural killer T cells (iNKT cells) are innate-like T lymphocytes that express a semi-invariant &#945;&#946; T cell receptor (TCR), formed in mice by an invariant V&#945;14-J&#945;18 chain paired with a limited set of diverse V&#946; chains1, which is specific for lipid antigens presented by the MHC class I-related molecule CD1d2. iNKT cells undergo an agonist selection program resulting in the acquisition of an activated/innate effector phenotype already in the thymus, which occurs through several maturation stages3,4, producing a CD4+ and a CD4- subset. Through this program, iNKT cells acquire distinct T helper (TH) effector phenotypes, namely TH1 (iNKT1), TH2 (iNKT2) and TH17 (iNKT17), identifiable by the expression of the transcription factors T-bet, GATA3, PLZF, and ROR&#947;t, respectively5. iNKT cells recognize a range of microbial lipids but are also self-reactive against endogenous lipids that are upregulated in the context of pathological situations of cell stress and tissue damage, such as cancer and autoimmunity2. Upon activation, iNKT cells modulate the functions of other innate and adaptive immune effector cells via direct contact and cytokine production2.
The investigations of iNKT cells have been facilitated by mouse models, including CD1d-deficient or J&#945;18-deficient mice, and by the production of antigen-loaded CD1d tetramers plus the generation of monoclonal antibodies (mAbs) specific for the human semi-invariant TCR. However, the generation of primary mouse iNKT cell line has proved difficult. To better characterize the antitumor functions of iNKT cells and to utilize them for adoptive cell therapy, we set up a protocol to purify and expand splenic iNKT cells of iV&#945;14-J&#945;18 transgenic mice (iV&#945;14Tg)6, in which iNKT cells are 30 times more frequent than in wild type mice.
Expanded iNKT cells can be exploited for in vitro assays, and in vivo upon transfer back into mice. In this setting, for example, we have shown their potent anti-tumor effects7. Moreover, in vitro expanded iNKT cells are amenable to functional modification via gene transfer or editing prior to their injection in vivo8, allowing insightful functional analysis of molecular pathways, as well as paving the way for advanced cell therapies.

<table><tbody><tr><td>Ammonium-Chloride-Potassium (ACK) solution</td><td>in house</td><td></td><td>0.15M NH4Cl, 10mM KHCO3, 0.1mM EDTA, pH 7.2-7.4</td></tr><tr><td>anti-FITC Microbeads</td><td>Miltenyi Biotec</td><td>130-048-701</td><td></td></tr><tr><td>anti-PE Microbeads</td><td>Miltenyi Biotec</td><td>130-048-801</td><td></td></tr><tr><td>Brefeldin A</td><td>Sigma</td><td>B6542</td><td></td></tr><tr><td>CD19 -FITC</td><td>Biolegend</td><td>115506</td><td>clone 6D5</td></tr><tr><td>CD1d-tetramer -PE</td><td>NIH tetramer core facility</td><td></td><td>mouse PBS57-Cd1d-tetramers</td></tr><tr><td>CD4 -PeCy7</td><td>Biolegend</td><td>100528</td><td>clone RM4-5</td></tr><tr><td>Fc blocker</td><td>BD Bioscience</td><td>553142</td><td></td></tr><tr><td>Fetal Bovine Serum (FBS)</td><td>Euroclone</td><td>ECS0186L</td><td>heat-inactivated and filtered .22 before use</td></tr><tr><td>FOXP3 Transcription factor staining buffer</td><td>eBioscience</td><td>00-5523-00</td><td></td></tr><tr><td>H2 (IAb) -FITC</td><td>Biolegend</td><td>114406</td><td>clone AF6-120.1</td></tr><tr><td>hrIL-2</td><td>Chiron Corp</td><td></td><td></td></tr><tr><td>Ionomycin</td><td>Sigma</td><td>I0634</td><td></td></tr><tr><td>LD Columns</td><td>Miltenyi Biotec</td><td>130-042-901</td><td></td></tr><tr><td>LS Columns</td><td>Miltenyi Biotec</td><td>130-042-401</td><td></td></tr><tr><td>MACS buffer (MB)</td><td>in house</td><td></td><td>0.5% Bovine Serum Albumin (BSA; Sigma-Aldrich) and 2Mm EDTA</td></tr><tr><td>MS Columns</td><td>Miltenyi Biotec</td><td>130-042-201</td><td></td></tr><tr><td>Non-essential amino acids</td><td>Gibco</td><td>11140-035</td><td></td></tr><tr><td>Penicillin and streptomycin (Pen-Strep)</td><td>Lonza</td><td>15140-122</td><td></td></tr><tr><td>PermWash</td><td>BD Bioscience</td><td>51-2091KZ</td><td></td></tr><tr><td>PFA</td><td>Sigma</td><td>P6148</td><td></td></tr><tr><td>Phosphate buffered saline (PBS)</td><td>EuroClone</td><td>ECB4004L</td><td></td></tr><tr><td>PMA</td><td>Sigma</td><td>P1585</td><td></td></tr><tr><td>Pre-Separation Filters (30 &amp;micro;m)</td><td>Miltenyi Biotec</td><td>130-041-407</td><td></td></tr><tr><td>Recombinat Mouse IL-7</td><td>R&amp;amp;D System</td><td>407-ML-025</td><td></td></tr><tr><td>RPMI 1640 with glutamax</td><td>Gibco</td><td>61870-010</td><td></td></tr><tr><td>sodium pyruvate</td><td>Gibco</td><td>11360-039</td><td></td></tr><tr><td>TCR&amp;beta; -APC</td><td>Biolegend</td><td>109212</td><td>clone H57-597</td></tr><tr><td>&amp;alpha;CD3CD28 mouse T activator Dynabeads</td><td>Gibco</td><td>11452D</td><td></td></tr><tr><td>&amp;beta;-mercaptoethanol</td><td>Gibco</td><td>31350010</td><td></td></tr></tbody></table>

purification and expansion of mouse invariant natural killer t cells for in vitro and in vivo studies

Invariant Natural Killer T (iNKT) cells are innate-like T Lymphocytes expressing a conserved semi-invariant T cell receptor (TCR) specific for self or microbial lipid antigens presented by the non-polymorphic MHC class I-related molecule CD1d. Preclinical and clinical studies support a role for iNKT cells in cancer, autoimmunity and infectious diseases. iNKT cells are very conserved throughout species and their investigation has been facilitated by mouse models, including CD1d-deficient or iNKT-deficient mice, and the possibility to unequivocally detect them in mice and men with CD1d tetramers or mAbs specific for the semi-invariant TCR. However, iNKT cells are rare and they need to be expanded to reach manageable numbers for any study. Because the generation of primary mouse iNKT cell line in vitro has proven difficult, we have set up a robust protocol to purify and expand splenic iNKT cells from the iV&#945;14-J&#945;18 transgenic mice (iV&#945;14Tg), in which iNKT cells are 30 times more frequent. We show here that primary splenic iV&#945;14Tg iNKT cells can be enriched through an immunomagnetic separation process, yielding about 95-98% pure iNKT cells. The purified iNKT cells are stimulated by anti-CD3/CD28 beads plus IL-2 and IL-7, resulting in 30-fold expansion by day +14 of the culture with 85-99% purity. The expanded iNKT cells can be easily genetically manipulated, providing an invaluable tool to dissect mechanisms of activation and function in vitro and, more importantly, also upon adoptive transfer in vivo.

The protocol described in this manuscript enables to enrich iNKT cells from the spleen of iVa14-Ja18 transgenic mice through an immunomagnetic separation process summarized in Figure 1A. Total spleen T cells are first negatively selected by depleting B cells and monocytes, followed by iNKT cell positive immunomagnetic sorting with PBS-57 lipid antigen loaded CD1d tetramers, that enable to specifically stain only iNKT cells. This protocol yields about 2 x 106 of 95-98% pure iNKT ce...

Watch this Scientific Journal Video about Purification and Expansion of Mouse Invariant Natural Killer T Cells for in vitro and in vivo Studies at JoVE.com

Purification and Expansion of Mouse Invariant Natural Killer T Cells for in vitro and in vivo Studies

We describe a rapid and robust protocol to enrich invariant natural killer T (iNKT) cells from mouse spleen and expand them in vitro to suitable numbers for in vitro and in vivo studies.

Invariant Natural Killer T (iNKT) cells are innate-like T Lymphocytes expressing a conserved semi-invariant T cell receptor (TCR) specific for self or ...

purification-expansion-mouse-invariant-natural-killer-t-cells-for

Research

JoVE Journal

Immunology and Infection

4.1K Views.  IRCCS San Raffaele Scientific Institute. We describe a rapid and robust protocol to enrich invariant natural killer T (iNKT) cells from mouse spleen and expand them in vitro to suitable numbers for in vitro and in vivo studies.

Video: Purification and Expansion of Mouse Invariant Natural Killer T Cells for in vitro and in vivo Studies

Expansion, Purification, and Functional Assessment of Human Peripheral Blood NK Cells 

Natural killer (NK) cells play an important role in immune surveillance against a variety of infectious microorganisms and tumors. Limited availability of NK cells and ability to expand in vitro has restricted development of NK cell immunotherapy. Here we describe a method to efficiently expand vast quantities of functional NK cells ex vivo using K562 cells expressing membrane-bound IL21, as an artificial antigen-presenting cell (aAPC).
NK cell adoptive therapies to date have utilized a cell product obtained by steady-state leukapheresis of the donor followed by depletion of T cells or positive selection of NK cells. The product is usually activated in IL-2 overnight and then administered the following day 1. Because of the low frequency of NK cells in peripheral blood, relatively small numbers of NK cells have been delivered in clinical trials.
The inability to propagate NK cells in vitro has been the limiting factor for generating sufficient cell numbers for optimal clinical outcome. Some expansion of NK cells (5-10 fold over 1-2 weeks) has be achieved through high-dose IL-2 alone 2. Activation of autologous T cells can mediate NK cell expansion, presumably also through release of local cytokine 3. Support with mesenchymal stroma or artificial antigen presenting cells (aAPCs) can support the expansion of NK cells from both peripheral blood and cord blood 4. Combined NKp46 and CD2 activation by antibody-coated beads is currently marketed for NK cell expansion (Miltenyi Biotec, Auburn CA), resulting in approximately 100-fold expansion in 21 days.
Clinical trials using aAPC-expanded or -activated NK cells are underway, one using leukemic cell line CTV-1 to prime and activate NK cells5 without significant expansion. A second trial utilizes EBV-LCL for NK cell expansion, achieving a mean 490-fold expansion in 21 days6. The third utilizes a K562-based aAPC transduced with 4-1BBL (CD137L) and membrane-bound IL-15 (mIL-15)7, which achieved a mean NK expansion 277-fold in 21 days. Although, the NK cells expanded using K562-41BBL-mIL15 aAPC are highly cytotoxic in vitro and in vivo compared to unexpanded NK cells, and participate in ADCC, their proliferation is limited by senescence attributed to telomere shortening8. More recently a 350-fold expansion of NK cells was reported using K562 expressing MICA, 4-1BBL and IL159.
Our method of NK cell expansion described herein produces rapid proliferation of NK cells without senescence achieving a median 21,000-fold expansion in 21 days.

Expansion, Purification, and Functional Assessment of Human Peripheral Blood NK Cells

Here we describe a method to efficiently expand and purify large numbers of human NK cells and assess their function.

Natural killer (NK) cells play an important role in immune surveillance against a variety of infectious microorganisms and tumors. Limited availability of ...

Isolation of CD4+ T cells from Mouse Lymph Nodes Using Miltenyi MACS Purification

Isolation of cells from the primary source is a necessary step in many more complex protocols. Miltenyi offers kits to isolate cells from several organisms including humans, non-human primates, rat and, as we describe here, mice. Magnetic bead-based cell separation allows for either positive selection (or cell depletion) as well as negative selection. Here, we demonstrate negative selection of untouched or na ve CD4+ helper T cells. Using this standard protocol we typically purify cells that are &#8805; 96% pure CD4+/CD3+. This protocol is used in conjunction with the protocol Dissection and 2-Photon Imaging of Peripheral Lymph Nodes in Mice published in issue 7 of JoVE, for purification of T cells and other cell types to adoptively transfer for imaging purposes. Although we did not demonstrate FACS analysis in this protocol video, it is highly recommended to check the overall purity of isolated cells using the appropriate antibodies via FACS. In addition, we demonstrate the non-sterile method of T cell isolation. If sterile cells are needed for your particular end-user application, be sure to do all of the demonstrated procedures in the tissue culture hood under standard sterile conditions. Thank you for watching and good luck with your own experiments!

Isolation of lymphocytes using the Miltenyi MACs kit is a reliable way to purify cells from whole lymphoid tissue homogenates. Cells purified using the Miltenyi system are typically &#8805; 96% pure. Here, we demonstrate the steps taken to isolate CD4+ T cells, one of the many kits offered by Miltenyi.

Isolation of cells from the primary source is a necessary step in many more complex protocols. Miltenyi offers kits to isolate cells from several ...

Biology

Mouse Na&#239;ve CD4+ T Cell Isolation and In vitro Differentiation into T Cell Subsets

Antigen inexperienced (na&#239;ve) CD4+ T cells undergo expansion and differentiation to effector subsets at the time of T cell receptor (TCR) recognition of cognate antigen presented on MHC class II. The cytokine signals present in the environment at the time of TCR activation are a major factor in determining the effector fate of a na&#239;ve CD4+ T cell. Although the cytokine environment during na&#239;ve T cell activation may be complex and involve both redundant and opposing signals in vivo, the addition of various cytokine combinations during naive CD4+ T cell activation in vitro can readily promote the establishment of effector T helper lineages with hallmark cytokine and transcription factor expression. Such differentiation experiments are commonly used as a first step for the evaluation of targets believed to promote or inhibit the development of certain CD4+ T helper subsets. The addition of mediators, such as signaling agonists, antagonists, or other cytokines, during the differentiation process can also be used to study the influence of a particular target on T cell differentiation. Here, we describe a basic protocol for the isolation of na&#239;ve T cells from mouse and the subsequent steps necessary for polarizing na&#239;ve cells to various T helper effector lineages in vitro.

Mouse Na&#239;ve CD4+ T Cell Isolation and In vitro Differentiation into T Cell Subsets

Na&#239;ve CD4+ T cells polarize to various subsets depending on the environment at the time of activation. The differentiation of na&#239;ve CD4+ T cells to various effector subsets can be achieved in vitro through the addition of T cell receptor stimuli and specific cytokine signals.

Antigen inexperienced (na&#239;ve) CD4+ T cells undergo expansion and differentiation to effector subsets at the time of T cell receptor (TCR) recognition ...

An Optimized Method for Isolating and Expanding Invariant Natural Killer T Cells from Mouse Spleen

The ability to rapidly secrete cytokines upon stimulation is a functional characteristic of the invariant natural killer T (iNKT) cell lineage. iNKT cells are therefore characterized as an innate T cell population capable of activating and steering adaptive immune responses. The development of improved techniques for the culture and expansion of murine iNKT cells facilitates the study of iNKT cell biology in in vitro and in vivo model systems. Here we describe an optimized procedure for the isolation and expansion of murine splenic iNKT cells.
Spleens from C57Bl/6 mice are removed, dissected and strained and the resulting cellular suspension is layered over density gradient media. Following centrifugation, splenic mononuclear cells (MNCs) are collected and CD5-positive (CD5+) lymphocytes are enriched for using magnetic beads. iNKT cells within the CD5+ fraction are subsequently stained with &#945;GalCer-loaded CD1d tetramer and purified by fluorescence activated cell sorting (FACS). FACS sorted iNKT cells are then initially cultured in vitro using a combination of recombinant murine cytokines and plate-bound T cell receptor (TCR) stimuli before being expanded in the presence of murine recombinant IL-7. Using this technique, approximately 108 iNKT cells can be generated within 18-20 days of culture, after which they can be used for functional assays in vitro, or for in vivo transfer experiments in mice.

Here we present an adapted protocol that can be used to generate a large number of murine invariant natural killer T cells from mouse spleen. The protocol outlines an approach by which splenic iNKT cells can be enriched for, isolated and expanded in vitro using a limited number of animals and reagents.

The ability to rapidly secrete cytokines upon stimulation is a functional characteristic of the invariant natural killer T (iNKT) cell lineage. iNKT cells ...

An Efficient and High Yield Method for Isolation of Mouse Dendritic Cell Subsets

Dendritic cells (DCs) are professional antigen-presenting cells primarily responsible for acquiring, processing and presenting antigens on antigen presenting molecules to initiate T-cell-mediated immunity. Dendritic cells can be separated into several phenotypically and functionally heterogeneous subsets. Three important subsets of splenic dendritic cells are plasmacytoid, CD8&#945;Pos and CD8&#945;Neg cells. The plasmacytoid DCs are natural producers of type I interferon and are important for anti-viral T cell immunity. The CD8&#945;Neg DC subset is specialized for MHC class II antigen presentation and is centrally involved in priming CD4 T cells. The CD8&#945;Pos DCs are primarily responsible for cross-presentation of exogenous antigens and CD8 T cell priming. The CD8&#945;Pos DCs have been demonstrated to be most efficient at the presentation of glycolipid antigens by CD1d molecules to a specialized T cell population known as invariant natural killer T (iNKT) cells. Administration of Flt-3 ligand increases the frequency of migration of dendritic cell progenitors from bone marrow, ultimately resulting in expansion of dendritic cells in peripheral lymphoid organs in murine models. We have adapted this model to purify large numbers of functional dendritic cells for use in cell transfer experiments to compare in vivo proficiency of different DC subsets.

Distinct dendritic cell subsets exist as rare populations in lymphoid organs, and therefore are challenging to isolate in sufficient numbers and purity for immunological experiments. Here we describe a high efficiency, high yield method for isolation of all of the currently known major subsets of mouse splenic dendritic cells.

Dendritic cells (DCs) are professional antigen-presenting cells primarily responsible for acquiring, processing and presenting antigens on antigen ...

Isolation and Activation of Murine Lymphocytes

B and T cells, with their extremely diverse antigen-receptor repertoires, have the ability to mount specific immune responses against almost any invading pathogen1,2. Understandably, such intricate abilities are controlled by a large number of molecules involved in various cellular processes to ensure timely and spatially regulated immune responses3. Here, we describe experimental procedures that allow rapid isolation of highly purified murine lymphocytes using magnetic cell sorting technology. The resulting purified lymphocytes can then be subjected to various in vitro or in vivo functional assays, such as the determination of lymphocyte signaling capacity upon stimulation by immunoblotting4 and the investigation of proliferative abilities by 3H-thymidine incorporation or carboxyfluorescein diacetate succinimidyl ester (CFSE) labeling5-7. In addition to comparing the functional capacities of control and genetically modified lymphocytes, we can also determine the T cell stimulatory capacity of antigen-presenting cells (APCs) in vivo, as shown in our representative results using transplanted CFSE-labeled OT-I T cells.

Lymphocytes are the major players in adaptive immune responses. Here, we present a lymphocyte purification protocol to determine the physiological functions of the desired molecules in lymphocyte activation in vitro and in vivo. The described experimental procedures are suitable for comparing functional capacities between control and genetically modified lymphocytes.

B and T cells, with their extremely diverse antigen-receptor repertoires, have the ability to mount specific immune responses against almost any invading ...

An In Vivo Mouse Model to Measure Na&#239;ve CD4 T Cell Activation, Proliferation and Th1 Differentiation Induced by Bone Marrow-derived Dendritic Cells

Quantification of na&#239;ve CD4 T cell activation, proliferation, and differentiation to T helper 1 (Th1) cells is a useful way to assess the role played by T cells in an immune response. This protocol describes the in vitro differentiation of bone marrow (BM) progenitors to obtain granulocyte macrophage colony-stimulating factor (GM-CSF) derived-dendritic cells (DCs). The protocol also describes the adoptive transfer of ovalbumin peptide (OVAp)-loaded GM-CSF-derived DCs and na&#239;ve CD4 T cells from OTII transgenic mice in order to analyze the in vivo activation, proliferation, and Th1 differentiation of the transferred CD4 T cells. This protocol circumvents the limitation of purely in vivo methods imposed by the inability to specifically manipulate or select the studied cell population. Moreover, this protocol allows studies in an in vivo environment, thus avoiding alterations to functional factors that may occur in vitro and including the influence of cell types and other factors only found in intact organs. The protocol is a useful tool for generating changes in DCs and T cells that modify adaptive immune responses, potentially providing important results to understand the origin or development of numerous immune associated diseases.

Here, we present a protocol for the in vivo determination of na&#239;ve CD4 T cell (T cell) activation, proliferation, and Th1 differentiation induced by GM-CSF bone marrow (BM)-derived dendritic cells (DCs). In addition, this protocol describes BM and T-cell isolation, DC generation, and DC and T-cell adoptive transfer.

Quantification of na&#239;ve CD4 T cell activation, proliferation, and differentiation to T helper 1 (Th1) cells is a useful way to assess the role played ...

Tailoring In Vivo Cytotoxicity Assays to Study Immunodominance in Tumor-specific CD8+ T Cell Responses

Carboxyfluorescein succinimidyl ester (CFSE)-based in vivo cytotoxicity assays enable sensitive and accurate quantitation of CD8+ cytolytic T lymphocyte (CTL) responses elicited against tumor- and pathogen-derived peptides. They offer several advantages over traditional killing assays. First, they permit the monitoring of CTL-mediated cytotoxicity within architecturally intact secondary lymphoid organs, typically in the spleen. Second, they allow for mechanistic studies during the priming, effector and recall phases of CTL responses. Third, they provide useful platforms for vaccine/drug efficacy testing in a truly in vivo setting. Here, we provide an optimized protocol for the examination of concomitant CTL responses against more than one peptide epitope of a model tumor antigen (Ag), namely, simian virus 40 (SV40)-encoded large T Ag (T Ag). Like most other clinically relevant tumor proteins, T Ag harbors many potentially immunogenic peptides. However, only four such peptides induce detectable CTL responses in C57BL/6 mice. These responses are consistently arranged in a hierarchical order based on their magnitude, which forms the basis for TCD8 &#8220;immunodominance&#8221; in this powerful system. Accordingly, the bulk of the T Ag-specific TCD8 response is focused against a single immunodominant epitope while the other three epitopes are recognized and responded to only weakly. Immunodominance compromises the breadth of antitumor TCD8 responses and is, as such, considered by many as an impediment to successful vaccination against cancer. Therefore, it is important to understand the cellular and molecular factors and mechanisms that dictate or shape TCD8 immunodominance. The protocol we describe here is tailored to the investigation of this phenomenon in the T Ag immunization model, but can be readily modified and extended to similar studies in other tumor models. We provide examples of how the impact of experimental immunotherapeutic interventions can be measured using in vivo cytotoxicity assays.

Tailoring In Vivo Cytotoxicity Assays to Study Immunodominance in Tumor-specific CD8+ T Cell Responses

We describe here a flow cytometry-based in vivo killing assay that enables examination of immunodominance in cytotoxic T lymphocyte (CTL) responses to a model tumor antigen. We provide examples of how this elegant assay may be employed for mechanistic studies and for drug efficacy testing.

Carboxyfluorescein succinimidyl ester (CFSE)-based in vivo cytotoxicity assays enable sensitive and accurate quantitation of CD8+ cytolytic T lymphocyte ...

Isolation of Uterine Innate Lymphoid Cells for Analysis by Flow Cytometry

Described here is a simple method to isolate and phenotype mouse group 1 uterine innate lymphoid cells (g1 uILCs) from individual pregnant uterus by flow cytometry. The protocol describes how to set up time mating to obtain multiple synchronous dams, the mechanical and enzymatic digestion of the pregnant uterus, the staining of single-cell suspensions, and a FACS strategy to phenotype and discriminate g1 uILCs. Although this method inevitably loses the spatial information of cellular distribution within the tissue, the protocol has been successfully applied to determine uILC heterogeneity, their response to maternal and foetal factors affecting pregnancy, their gene expression profile, and their functions.

This is a method to isolate uterine lymphoid cells from both pregnant and non-pregnant mice. This method can be used for multiple downstream applications such as FACS phenotyping, cell sorting, functional assays, RNA-seq, and proteomics. The protocol here demonstrates how to phenotype group 1 uterine innate lymphoid cells by flow cytometry.

Described here is a simple method to isolate and phenotype mouse group 1 uterine innate lymphoid cells (g1 uILCs) from individual pregnant uterus by flow ...

Natural Killer Cell Isolation from Liver Tissue for Selective Expansion

Begin by identifying and sectioning the viable tissue areas using sterile surgical equipment to obtain lymphocytes. Then, place the sectioned tissues in 30 milliliters of HBSS without calcium or magnesium, and keep the tissue on ice until ready for isolation.
Working inside a biosafety cabinet, mince the tissue into less than 0.5-centimeter cubes with sterile razor blades and forceps. Place the minced tissue pieces &#8212; not more than 4 grams &#8212; in the tissue dissociator tubes, and add 10 milliliters of collagenase IV to the tissue pieces.
To mince the tissue thoroughly, treat the tissue dissociator tubes into a tissue dissociator at 37 degrees Celsius. After removing the tubes from the tissue dissociator, triturate the minced tissue through a 40-micron nylon cell strainer using the back end of a 5-milliliter syringe. Discard the large, undigested fragments.
Spin down the collected eluent at 400 g for 5 minutes at room temperature, and aspirate the supernatant before resuspending the cell pellets in 30% polyvinylpyrrolidone-coated silica to remove the fat cells. Spin down the cells as described, before resuspending the cell pellet in 9 milliliters of R-10 media.
To separate lymphocytes from red blood cells and polymorphonuclear cells, carefully layer the cell suspension over 4 milliliters of Ficoll or lymphocyte separation media. Separate the layers by centrifuging at 400 g for 23 minutes at room temperature with the acceleration and brakes off. Then, carefully decant the upper medium layer and harvest the interphase containing tissue-infiltrating lymphocytes.
Rinse the cells with 10 milliliters of media and proceed for analysis of primary Natural Killer, or NK, cells expansion protocol.

Purification and Expansion of Mouse Invariant Natural Killer T Cells for in vitro and in vivo Studies

Summary

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