The present study was supported financially by the Swedish Research Council, EXODIAB, the Swedish Diabetes Foundation, the Swedish Child Diabetes Fund, SEB Diabetesfonden and O.E. och Edla Johanssons vetenskapliga stiftelse. Authors would also like to thanks Per-Ola Carlsson and Stellan Sandler for their supports and discussions.

The local animal ethics committee at Uppsala University approved the animal experiments.
1. Harvesting Organs from Animals
<ol>
	<li>Sacrifice the mice by cervical dislocation.</li>
	<li>Place thymic glands and spleens in 20 mL scintillation vials or 15 mL conical tubes filled with 5 mL of Hanks&#180; balanced salt solution (HBSS). Place PDLNs in 1.5 mL micro tubes filled with 1 mL of RPMI 1640. Use the whole thymus and spleen, and all the PDLNs. 
	NOTE: Organs should be kept on ice throughout the procedure and the investigator should try to be fast while preparing single cell suspensions, especially when handling thymic tissue since thymic immune cells can be quickly degraded at high temperatures.</li>
</ol>
2. Single Cell Isolation from Thymus and Spleen
<ol>
	<li>Thoroughly squeeze the thymus and spleen with a pair of tweezers to release the immune cells. Discard the remaining thymic and splenic capsule.</li>
	<li>Transfer the cell suspension to a 15 mL conical tube and centrifuge at 433 x g for 5 min at 4 &#176;C to form a pellet. Discard the supernatant.</li>
	<li>To lyse the red blood cells, resuspend the cell suspension in 5 mL of 0.2 M NH4Cl and incubate at room temperature for 10 min. Invert the tubes upside down gently every 2 min. Add 5 mL of HBSS at the end of the incubation to stop the lysis.</li>
	<li>Centrifuge the tubes at 433 x g for 5 min at 4 &#176;C. Discard the supernatant.</li>
	<li>Resuspend the cell pellet in approximately 5 mL of HBSS. Fill the tubes with HBSS.</li>
	<li>Centrifuge the tubes at 433 x g for 5 min at 4 &#176;C. Discard the supernatant.</li>
	<li>Resuspend the cell pellet in approximately 5 mL of HBSS. Fill the tubes with HBSS.</li>
	<li>Centrifuge the tubes at 433 x g for 5 min at 4 &#176;C. Discard the supernatant.</li>
	<li>Resuspend the cell pellet in in 5 mL of HBSS for thymus and 10 mL for spleen.</li>
	<li>Transfer 1 mL of the thymic cell suspension and 500 &#181;L of the splenic cell suspension to 5 mL round bottom tubes with cell strainer caps. Apply the cell suspension to the cell strainer caps. 
	NOTE: A 35 &#181;m nylon mesh is incorporated into the cap. Approximately 5-10 million cells were collected in each tube.</li>
</ol>
3. Single Cell Isolation from PDLN
<ol>
	<li>Place a sterile 250 &#181;m metal mesh over a 15 mL conical tube in a rack. Rinse the mesh with 1 mL of RPMI.</li>
	<li>Transfer the lymph nodes to the metal mesh and grind them through the mesh using a pair of tweezers. Apply 1 mL of RPMI on the metal mesh to flush the cells into the tube. Repeat 3 more times and remove the mesh.</li>
	<li>Centrifuge the tubes at 433 x g for 5 min at 4 &#176;C. Discard the supernatant.</li>
	<li>Resuspend the cell pellet in approximately 5 mL of RPMI. Fill the tubes with RPMI.</li>
	<li>Centrifuge the tubes at 433 x g for 5 min at 4 &#176;C. Discard the supernatant.</li>
	<li>Resuspend the cell pellet in approximately 5 mL of RPMI. Fill the tubes with RPMI.</li>
	<li>Centrifuge the tubes at 433 x g for 5 min at 4 &#176;C. Discard the supernatant.</li>
	<li>Resuspend the cell pellet in 2 mL of RPMI. Transfer 2 mL of the cell suspension to 5 mL round bottom tubes with cell strainer caps. Apply the cell suspension to the cell strainer caps.</li>
</ol>
4. Flow Cytometry
<ol>
	<li>Centrifuge the cell suspensions from thymus, PDLN and spleen at 433 x g for 5 min at 4 &#176;C. Discard the supernatant.</li>
	<li>Stain the cells with the following surface antibodies in 100 &#181;L of flow cytometry staining buffer (FACS buffer): 0.75 &#181;g/100 &#181;L FITC-conjugated CD4 antibody, 0.60 &#181;g/100 &#181;L APC-H7-conjugated CD8 antibody, 0.30 &#181;g/100 &#181;L PE-conjugated CD25 antibody, 5 &#181;L (1: 20) APC-conjugated Nrp1 antibody. Incubate the tubes on ice for 40 min.</li>
	<li>Add 200 &#181;L of FACS buffer to each tube. Centrifuge the tubes at 433 x g for 5 min at 4 &#176;C. Discard the supernatant. Repeat one more time.</li>
	<li>Fix and permeabilize the cells by resuspending the cell pellet in 500 &#181;L of Permeabilization Fixation Buffer (PFB). 
	NOTE: PFB is prepared by mixing 1 part of Fixation/Permeabilization Concentrate with 3 parts of Fixation/Permeabilization Diluent.</li>
	<li>Keep the tubes in the fridge at 4 &#176;C overnight. 
	NOTE: A 1 h incubation also works.</li>
	<li>Centrifuge the tubes at 433 x g for 5 min at 4 &#176;C. Discard the supernatant.</li>
	<li>Resuspend the cell pellet in 500 &#181;L of Permeabilization Washing Buffer (PWB). Centrifuge the tubes at 433 x g for 5 min at 4 &#176;C. Discard the supernatant. 
	NOTE: PWB is prepared by diluting Permeabilization Buffer (10x) to 1:10 in distilled water.</li>
	<li>Stain the cells with the following intracellular antibodies in 100 &#181;L of PWB: 0.30 &#181;g/100 &#181;L PE-Cy7-conjugated Foxp3 antibody, 4 &#181;L (1: 25) PacificBlue-conjugated Helios antibody. Incubate the tubes on ice for 1 h.</li>
	<li>Add 500 &#181;L of PWB to each tube. Centrifuge the tubes at 433 x g for 5 min at 4 &#176;C. Discard the supernatant.</li>
	<li>Resuspend the cell pellet in 500 &#181;L of PWB. Centrifuge the tubes at 433 x g for 5 min at 4 &#176;C. Discard the supernatant.</li>
	<li>Resuspend the cell pellet in 300 &#181;L of FACS buffer.</li>
	<li>Analyze the cells on a flow cytometer.</li>
	<li>Gate the single cells based on Side Scatter-Area, Height and Width, and Forward Scatter-Area, Height and Width. Run one million events for analysis.</li>
	<li>Export the FCS files of experiments and analyze them using a flow cytometry analyzer software.</li>
</ol>

<ol>
	<li>Fontenot, J. D., Gavin, M. A., Rudensky, A. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Foxp3+programs+the+development+and+function+of+CD4+CD25++regulatory+T+cells.">Foxp3 programs the development and function of CD4+CD25+ regulatory T cells.</a> Nature Immunology. 4 (4), 330-336 (2003).</li><li>Khattri, R., Cox, T., Yasayko, S. A., Ramsdell, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+essential+role+for+Scurfin+in+CD4+CD25++T+regulatory+cells.">An essential role for Scurfin in CD4+CD25+ T regulatory cells.</a> Nature Immunology. 4 (4), 337-342 (2003).</li><li>Hori, S., Nomura, T., Sakaguchi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+regulatory+T+cell+development+by+the+transcription+factor+Foxp3.">Control of regulatory T cell development by the transcription factor Foxp3.</a> Science. 299 (5609), 1057-1061 (2003).</li><li>Sakaguchi, S., Sakaguchi, N., Asano, M., Itoh, M., Toda, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunologic+self-tolerance+maintained+by+activated+T+cells+expressing+IL-2+receptor+alpha-chains+(CD25).+Breakdown+of+a+single+mechanism+of+self-tolerance+causes+various+autoimmune+diseases.">Immunologic self-tolerance maintained by activated T cells expressing IL-2 receptor alpha-chains (CD25). Breakdown of a single mechanism of self-tolerance causes various autoimmune diseases.</a> The Journal of Immunology. 155 (3), 1151-1164 (1995).</li><li>Vignali, D. A., Collison, L. W., Workman, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+regulatory+T+cells+work.">How regulatory T cells work.</a> Nature Review Immunology. 8 (7), 523-532 (2008).</li><li>Thornton, A. 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=Expression+of+Helios,+an+Ikaros+transcription+factor+family+member,+differentiates+thymic-derived+from+peripherally+induced+Foxp3++T+regulatory+cells.">Expression of Helios, an Ikaros transcription factor family member, differentiates thymic-derived from peripherally induced Foxp3+ T regulatory cells.</a> The Journal of Immunology. 184 (7), 3433-3441 (2010).</li><li>Weiss, J. 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=Neuropilin+1+is+expressed+on+thymus-derived+natural+regulatory+T+cells,+but+not+mucosa-generated+induced+Foxp3++T+reg+cells.">Neuropilin 1 is expressed on thymus-derived natural regulatory T cells, but not mucosa-generated induced Foxp3+ T reg cells.</a> Journal of Experimental Medicine. 209 (10), 1723-1742 (2012).</li><li>Yadav, 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=Neuropilin-1+distinguishes+natural+and+inducible+regulatory+T+cells+among+regulatory+T+cell+subsets+in+vivo.">Neuropilin-1 distinguishes natural and inducible regulatory T cells among regulatory T cell subsets in vivo.</a> Journal of Experimental Medicine. 209 (10), S1711-S1719 (2012).</li><li>Singh, K., Hjort, M., Thorvaldson, L., Sandler, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concomitant+analysis+of+Helios+and+Neuropilin-1+as+a+marker+to+detect+thymic+derived+regulatory+T+cells+in+naive+mice.">Concomitant analysis of Helios and Neuropilin-1 as a marker to detect thymic derived regulatory T cells in naive mice.</a> Scientific Reports. 5, 7767 (2015).</li><li>Jungblut, M., Oeltze, K., Zehnter, I., Hasselmann, D., Bosio, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+single-cell+suspensions+from+mouse+spleen+with+the+gentleMACS+Dissociator.">Preparation of single-cell suspensions from mouse spleen with the gentleMACS Dissociator.</a> Journal of Visualized Experiments. (22), (2008).</li><li>Jungblut, M., Oeltze, K., Zehnter, I., Hasselmann, D., Bosio, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standardized+preparation+of+single-cell+suspensions+from+mouse+lung+tissue+using+the+gentleMACS+Dissociator.">Standardized preparation of single-cell suspensions from mouse lung tissue using the gentleMACS Dissociator.</a> Journal of Visualized Experiments. (29), (2009).</li><li>Singh, K., 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=Interleukin-35+administration+counteracts+established+murine+type+1+diabetes--possible+involvement+of+regulatory+T+cells.">Interleukin-35 administration counteracts established murine type 1 diabetes--possible involvement of regulatory T cells.</a> Scientific Reports. 5, 12633 (2015).</li><li>Digre, 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=Overexpression+of+heparanase+enhances+T+lymphocyte+activities+and+intensifies+the+inflammatory+response+in+a+model+of+murine+rheumatoid+arthritis.">Overexpression of heparanase enhances T lymphocyte activities and intensifies the inflammatory response in a model of murine rheumatoid arthritis.</a> Scientific Reports. 7, 46229 (2017).</li><li>Li, X., 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=Pro-tumoral+immune+cell+alterations+in+wild+type+and+Shb-deficient+mice+in+response+to+4T1+breast+carcinomas.">Pro-tumoral immune cell alterations in wild type and Shb-deficient mice in response to 4T1 breast carcinomas.</a> Oncotarget. 9 (27), 18720-18733 (2018).</li></ol>

The authors have nothing to disclose.

In this study, we isolated single cells from thymic glands, PDLNs and spleens of NOD mice, and investigated the expression of Helios and Nrp1 in CD4+CD8-CD25+Foxp3+ Treg cells using flow cytometry. In the present study, NOD mice were used, which is a murine model of type 1 diabetes. In a previous study, we have used the wild type mouse strains CD-1 and C57BL/6 mice to investigate whether Helios or Nrp1 is a better marker for distinguishing tTreg cells from pTreg cells. In that ...

Regulatory T (Treg) cells are critical for the homeostasis of immune system. Treg cells are defined by the expression of surface antigens CD4 and CD25, and the transcription factor forkhead box P3 (Foxp3)1,2,3. Sakaguchi et al. first showed that CD25 is constitutively expressed on T suppressor cells in mice4, which provided a pioneering observation for the identification of human Treg cells. Treg cells play a central role in immune tolerance by exerting a suppressive ability via a variety of mechanisms, including cytolysis through the secretion of granzymes to induce apoptosis, cytokine consumption and inhibition through the expression of cytotoxic T-lymphocyte antigen 45. Additionally, they can secrete inhibitory cytokines such as transforming growth factor beta (TGF-&#946;), interleukin-10 (IL-10) and IL-355. Treg cells can naturally be derived from the thymus, in which case they are designated thymic derived Treg (tTreg) cells, or they can be induced in the peripheral organs in that case are called peripherally induced Treg (pTreg) cells.
Helios, a member of the Ikaros transcription factor family, was reported to be a marker for distinguishing between tTreg cells and pTreg cells6. Later, two other groups reported that Neuropilin 1 (Nrp1), a semaphorin III receptor, could serve as a surface marker for tTreg cells under certain conditions7,8. Nevertheless, Singh et al. have shown that Helios is a better marker in this context in na&#239;ve mice9.
The subsets of Treg cells play a pivotal role in the maintenance of the homeostasis of the immune system and in the protection against autoimmunity and infection. Therefore, it is important to determine the numbers and proportions of these populations in both lymphoid and non-lymphoid tissues. To achieve this, one has to prepare single cell suspensions from these organs. A number of protocols have been described or used in previous studies. Mainly, automatic dissociators have been used in previously published reports10,11. Using automatic dissociators is convenient and time saving, but it is an expensive procedure. Therefore, we have used a manual method to prepare single cell suspensions from murine thymic glands, pancreatic draining lymph nodes (PDLNs) and spleens from normoglycemic non-obese diabetic (NOD) mice, and isolated single cells from these organs. This method has been used in our previous studies and we found that the manual method for preparing single cell suspension is as efficient as automatic dissociator method9,12,13,14. Furthermore, we used flow cytometry to determine the proportions of CD4+CD8-CD25+Foxp3+ Treg cells and the subsets of Treg cells tTreg and pTreg cells. The tTreg and pTreg cells were distinguished using Helios and Nrp1 as markers for tTreg cell. Thus, our results indicate that the manual method for preparing the single cells does work efficiently and the prepared single cell suspensions can be further used for studies using flow cytometry.

<table>
	<tbody>
		<tr>
			<td>NOD mice</td>
			<td></td>
			<td></td>
			<td>In-house breading</td>
		</tr>
		<tr>
			<td>HBSS</td>
			<td>Statens veterin&#228;rmedicinska anstalt</td>
			<td>991750</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI-1640</td>
			<td>Sigma-Aldrich</td>
			<td>R0883-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>NH4Cl</td>
			<td>EMD Millipore</td>
			<td>1011450500</td>
			<td></td>
		</tr>
		<tr>
			<td>eBioscience Foxp3 / Transcription Factor Staining Buffer Set</td>
			<td>ThermoFisher</td>
			<td>00-5523-00</td>
			<td>Contains Fixation/Permeabilization Concentrate , Fixation/Permeabilization Diluent and Permeabilization Buffer (10X)</td>
		</tr>
		<tr>
			<td>eBioscience Flow Cytometry Staining Buffer</td>
			<td>ThermoFisher</td>
			<td>00-4222-26</td>
			<td></td>
		</tr>
		<tr>
			<td>CD4 Monoclonal Antibody (RM4-5), FITC, eBioscience</td>
			<td>ThermoFisher</td>
			<td>11-0042-85</td>
			<td></td>
		</tr>
		<tr>
			<td>CD25 Monoclonal Antibody (PC61.5), PE, eBioscience</td>
			<td>ThermoFisher</td>
			<td>12-0251-83</td>
			<td></td>
		</tr>
		<tr>
			<td>BD Pharmingen&#160;APC-H7 Rat anti-Mouse CD8a</td>
			<td>BD Biosciences</td>
			<td>560182</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse Neuropilin-1 APC-conjugated Antibody</td>
			<td>R&#38;D Systems</td>
			<td>FAB5994A</td>
			<td></td>
		</tr>
		<tr>
			<td>FOXP3 Monoclonal Antibody (FJK-16s), PE-Cyanine7, eBioscience</td>
			<td>ThermoFisher</td>
			<td>25-5773-82</td>
			<td></td>
		</tr>
		<tr>
			<td>Pacific Blue anti-mouse/human Helios Antibody</td>
			<td>BioLegend</td>
			<td>137220</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon 5 mL Round Bottom Polystyrene Test Tube, with Cell Strainer Snap Cap</td>
			<td>CORNING</td>
			<td>352235</td>
			<td>A 35 &#181;m nylon mesh is incorporated into the dual-position snap cap</td>
		</tr>
		<tr>
			<td>Tube 15ml, 120x17mm, PP</td>
			<td>Sarstedt</td>
			<td>62.554.002</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro tube 1.5ml</td>
			<td>Sarstedt</td>
			<td>72.690.001</td>
			<td></td>
		</tr>
		<tr>
			<td>disposable scintillation vials</td>
			<td>WHEATON</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Flow cytometry</td>
			<td>BD</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Flow cytometry analysis software</td>
			<td>Inivai Technologies</td>
			<td>Flowlogic</td>
			<td></td>
		</tr>
	</tbody>
</table>

determination of regulatory t cell subsets in murine thymus, pancreatic draining lymph node and spleen using flow cytometry

Our immune system consists of a number and variety of immune cells including regulatory T cells (Treg) cells. Treg cells can be divided into two subsets, thymic derived Treg (tTreg) cells and peripherally induced Treg (pTreg) cells. They are present in different organs of our body and can be distinguished by specific markers, such as Helios and Neuropilin 1. It has been reported that tTreg cells are functionally more suppressive than pTreg cells. Therefore, it is important to determine the proportion of both tTreg and pTreg cells when investigating heterogeneous cell populations. Herein, we collected thymic glands, pancreatic draining lymph nodes and spleens from normoglycemic non-obese diabetic mice to distinguish tTreg cells from pTreg cells using flow cytometry. We manually prepared single cell suspensions from these organs. Fluorochrome conjugated surface CD4, CD8, CD25, and Neuropilin 1 antibodies were used to stain the cells. They were kept in the fridge overnight. On the next day, the cells were stained with fluorochrome conjugated intracellular Foxp3 and Helios antibodies. These markers were used to characterize the two subsets of Treg cells. This protocol demonstrates a simple but practical way to prepare single cells from murine thymus, pancreatic draining lymph node and spleen and use them for subsequent flow cytometric analysis.

To investigate the expression of Nrp1 and Helios on tTreg and pTreg cells, we prepared single cells from thymic glands, PDLNs and spleens of normoglycemic NOD mice and stained them with the Treg cell markers CD4, CD25, Foxp3, Helios and Nrp1 for flow cytometric analysis. The results were analyzed as shown in the representative gating strategies (Figure 1). We found that the proportion of Helios+ cells among CD4+CD8-CD25+<...

Watch this Scientific Journal Video about Determination of Regulatory T Cell Subsets in Murine Thymus, Pancreatic Draining Lymph Node and Spleen Using Flow Cytometry at JoVE.com

Determination of Regulatory T Cell Subsets in Murine Thymus, Pancreatic Draining Lymph Node and Spleen Using Flow Cytometry

Herein, we present a protocol to prepare single cells from murine thymus, pancreatic draining lymph node and spleen to further study these cells using flow cytometry. In addition, this protocol was used for determining the subsets of regulatory T cells using flow cytometry.

Our immune system consists of a number and variety of immune cells including regulatory T cells (Treg) cells. Treg cells can be divided into two subsets, ...

determination-regulatory-t-cell-subsets-murine-thymus-pancreatic

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JoVE Journal

Immunology and Infection

11.2K Views.  Uppsala University. Herein, we present a protocol to prepare single cells from murine thymus, pancreatic draining lymph node and spleen to further study these cells using flow cytometry. In addition, this protocol was used for determining the subsets of regulatory T cells using flow cytometry.

Video: Determination of Regulatory T Cell Subsets in Murine Thymus, Pancreatic Draining Lymph Node and Spleen Using Flow Cytometry

Non-surgical Intratracheal Instillation of Mice with Analysis of Lungs and Lung Draining Lymph Nodes by Flow Cytometry

Phagocytic cells such as alveolar macrophages and lung dendritic cells (LDCs) continuously sample antigens from the alveolar spaces in the 
lungs. LDCs, in particular, are known to migrate to the lung draining lymph nodes (LDLNs) where they present inhaled antigens to T cells initiating an 
appropriate immune response to a variety of immunogens1,2. To model interactions between the lungs and airborne antigens in mice, antigens can be 
administered intranasally1,3,4, intratracheally5 or as aerosols6. Delivery by each route involves distinct technical skills and limitations that need to be 
considered before designing an experiment. For example, intranasal and aerosolized exposure delivers antigens to both the lungs and the upper respiratory 
tract. Hence antigens can access the nasal associated lymphoid tissue (NALT)7, potentially complicating interpretation of the results. In addition, swallowing, 
sneezing and the breathing rate of the mouse may also lead to inconsistencies in the doses delivered. Although the involvement of the upper respiratory tract may 
be preferred for some studies, it can complicate experiments focusing on events specifically initiated in the lungs. In this setting, the intratracheal (i.t) 
route is preferable as it delivers test materials directly into the lungs and bypasses the NALT. Many i.t injection protocols involve either blind intubation of the 
trachea through the oral cavity or surgical exposure of the trachea to access the lungs. Herein, we describe a simple, consistent, non-surgical method for i.t 
instillation. The opening of the trachea is visualized using a laryngoscope and a bent gavage needle is then inserted directly into the trachea to deliver the 
innoculum. We also describe procedures for harvesting and processing of LDLNs and lungs for analysis of antigen trafficking by flow cytometry.

We illustrate non-surgical delivery of test materials into the lungs of anesthetized mice via the trachea. This method permits lung exposure to bacterial and viral pathogens, cytokines, antibodies, beads, chemicals, or dyes. We further describe harvesting and processing of lungs and lung draining lymph nodes (LDLNs) for flow cytometry.

Phagocytic cells such as alveolar macrophages and lung dendritic cells (LDCs) continuously sample antigens from the alveolar spaces in the 
lungs. LDCs, ...

Flow Cytometry Analysis of Immune Cells Within Murine Aortas

Atherosclerosis is a chronic inflammatory process of medium and large size vessels that is characterized by the formation of plaques consisting of foam cells, immune cells, vascular endothelial and smooth muscle cells, platelets, extracellular matrix, and a lipid-rich core with extensive necrosis and fibrosis of surrounding tissues.1 The innate and adaptive arms of the immune response are involved in the initiation, development and persistence of atherosclerosis.2, 3 There is a significant body of evidence that different subsets of the immune cells, such as macrophages, dendritic cells, T and B lymphocytes, are present within the aortas of healthy and atherosclerosis-prone mice4. Additionally, immune cells are found in the surrounding aortic adventitia which suggests an important role of this tissue in atherogenesis.2
For some time, the quantitative detection of different types of immune cells, their activation status, and the cellular composition within the aortic wall was limited by RT-PCR and immunohistochemical methods for the study of atherosclerosis. Few attempts were made to perform flow cytometry using human aortas, and a number of problems, such as a high autofluorescence, have been reported5,6. Human atherosclerotic plaques were digested with collagenase 1, and free cells were collected and stained for CD14+/CD11c+ to highlight macrophage-derived foam cells. In this study, a "mock" channel was used to avoid false-positive staining.6 Necrotic materials accumulating during the digestion process give rise in a large amount of debris that generates a high autofluorescence in aortic samples. To resolve this problem, a panel of negative and positive controls has been proposed, but only double staining could be applied in these samples. We have developed a new flow cytometry-based method7 to analyze the immune cell composition and characterize the activation, proliferation, differentiation of immune cells in healthy and atherosclerosis-prone aorta. This method allows the investigation of the immune cell composition of the aortic wall and opens possibilities to use a broad spectrum of immunological methods for investigations of immune aspects of this disease.

This paper presents a flow cytometry-based method to investigate the immune composition of aortas. The paper also illustrates an additional technique that allows examining surrounding adventitia and vessel wall separately. This method opens possibilities to perform phenotypical analyses of aortic leukocytes and apply several immunological assays for atherosclerosis studies.

Atherosclerosis is a chronic inflammatory process of medium and large size vessels that is characterized by the formation of plaques consisting of foam ...

Ex vivo Imaging of T Cells in Murine Lymph Node Slices with Widefield and Confocal Microscopes

Na&iuml;ve T cells continuously traffic to secondary lymphoid organs, including peripheral lymph nodes, to detect rare expressed antigens. The migration of T cells into lymph nodes is a complex process which involves both cellular and chemical factors including chemokines. Recently, the use of two-photon microscopy has permitted to track T cells in intact lymph nodes and to derive some quantitative information on their behavior and their interactions with other cells. While there are obvious advantages to an in vivo system, this approach requires a complex and expensive instrumentation and provides limited access to the tissue. To analyze the behavior of T cells within murine lymph nodes, we have developed a slice assay 
1, originally set up by neurobiologists and transposed recently to murine thymus 2. In this technique, fluorescently labeled T cells are plated on top of an acutely prepared lymph node slice. In this video-article, the localization and migration of T cells into the tissue are analyzed in real-time with a widefield and a confocal microscope. The technique which complements in vivo two-photon microscopy offers an effective approach to image T cells in their natural environment and to elucidate mechanisms underlying T cell migration.

Ex vivo Imaging of T Cells in Murine Lymph Node Slices with Widefield and Confocal Microscopes

This protocol describes a method to image fluorescent T cells introduced into lymph node slices. The technique permits real-time analyses of T cell migration with traditional widefield fluorescence or confocal microscopes.

Na&iuml;ve T cells continuously traffic to secondary lymphoid organs, including peripheral lymph nodes, to detect rare expressed antigens. The migration ...

Murine Superficial Lymph Node Surgery

In the field of immunology, to understand the progression of an immune response against a vaccine, an infection or a tumour, the response is often followed over time. Similarly, the study of lymphocyte homeostasis requires time course experiments. Performing these studies within the same mouse is ideal to reduce the experimental variability as well as the number of mice used. Blood withdrawal allows performance of time course experiments, but it only gives information about circulating lymphocytes and provides a limited number of cells1-4. Since lymphocytes circulating through the body and residing in the lymph nodes have different properties, it is important to examine both locations. The sequential removal of lymph nodes by surgery provides a unique opportunity to follow an immune response or immune cell expansion in the same mouse over time. Furthermore, this technique yields between 1-2x106 cells per lymph node which is sufficient to perform phenotypic characterization and/or functional assays. Sequential lymph node surgery or lymphadenectomy has been successfully used by us and others5-11. Here, we describe how the brachial and inguinal lymph nodes can be removed by making a small incision in the skin of an anesthetised mouse. Since the surgery is superficial and done rapidly, the mouse recovers very quickly, heals well and does not experience excessive pain. Every second day, it is possible to harvest one or two lymph nodes allowing for time course experiments. This technique is thus suitable to study the characteristics of lymph node-residing lymphocytes over time. This approach is suitable to various experimental designs and we believe that many laboratories would benefit from performing sequential lymph node surgeries.

To follow the progression of an immune response over time within the same mouse, lymph nodes can be sequentially removed by surgery. Here, we describe how this technique can be performed.

In the field of immunology, to understand the progression of an immune response against a vaccine, an infection or a tumour, the response is often ...

Intravital Imaging of the Mouse Popliteal Lymph Node

Lymph nodes (LNs) are secondary lymphoid organs, which are strategically located throughout the body to allow for trapping and presentation of foreign antigens from peripheral tissues to prime the adaptive immune response. Juxtaposed between innate and adaptive immune responses, the LN is an ideal site to study immune cell interactions1,2. Lymphocytes (T cells, B cells and NK cells), dendritic cells (DCs), and macrophages comprise the bulk of bone marrow-derived cellular elements of the LN. These cells are strategically positioned in the LN to allow efficient surveillance of self antigens and potential foreign antigens3-5. The process by which lymphocytes successfully encounter cognate antigens is a subject of intense investigation in recent years, and involves an integration of molecular contacts including antigen receptors, adhesion molecules, chemokines, and stromal structures such as the fibro-reticular network2,6-12. 
Prior to the development of high-resolution real-time fluorescent in vivo imaging, investigators relied on static imaging, which only offers answers regarding morphology, position, and architecture. While these questions are fundamental in our understanding of immune cell behavior, the limitations intrinsic with this technique does not permit analysis to decipher lymphocyte trafficking and environmental clues that affect dynamic cell behavior. Recently, the development of intravital two-photon laser scanning microscopy (2P-LSM) has allowed investigators to view the dynamic movements and interactions of individual cells within live LNs in situ12-16. In particular, we and others have applied this technique to image cellular behavior and interactions within the popliteal LN, where its compact, dense nature offers the advantage of multiplex data acquisition over a large tissue area with diverse tissue sub-structures11,17-18. It is important to note that this technique offers added benefits over explanted tissue imaging techniques, which require disruption of blood, lymph flow, and ultimately the cellular dynamics of the system. Additionally, explanted tissues have a very limited window of time in which the tissue remains viable for imaging after explant. With proper hydration and monitoring of the animal's environmental conditions, the imaging time can be significantly extended with this intravital technique. Here, we present a detailed method of preparing mouse popliteal LN for the purpose of performing intravital imaging.

Recent advances in 2-photon microscopy have enabled real-time in situ imaging of live tissues in animal models, thereby enhancing our ability to investigate cellular behavior in both physiologic and pathologic conditions. Here, we outline the preparations required to perform intravital imaging of the mouse popliteal lymph node.

Lymph nodes (LNs) are secondary lymphoid organs, which are strategically located throughout the body to allow for trapping and presentation of foreign ...

Generation of Lymph Node-fat Pad Chimeras for the Study of Lymph Node Stromal Cell Origin

The stroma is a key component of the lymph node structure and function. However, little is known about its origin, exact cellular composition and the mechanisms governing its formation. Lymph nodes are always encapsulated in adipose tissue and we recently demonstrated the importance of this relation for the formation of lymph node stroma. Adipocyte precursor cells migrate into the lymph node during its development and upon engagement of the Lymphotoxin-b receptor switch off adipogenesis and differentiate into lymphoid stromal cells (B&#233;n&#233;zech&#160;et al.14). Based on the lymphoid stroma potential of adipose tissue, we present a method using a lymph node/fat pad chimera that allows the lineage tracing of lymph node stromal cell precursors. We show how to isolate newborn lymph nodes and EYFP+ embryonic adipose tissue and make a LN/ EYFP+ fat pad chimera. After transfer under the kidney capsule of a host mouse, the lymph node incorporates local adipose tissue precursor cells and finishes its formation. Progeny analysis of EYFP+ fat pad cells in the resulting lymph nodes can be performed by flow-cytometric analysis of enzymatically digested lymph nodes or by immunofluorescence analysis of lymph nodes cryosections. By using fat pads from different knockout mouse models, this method will provide an efficient way of analyzing the origin of the different lymph node stromal cell populations.

Generation of lymph node/fat pad chimeras for the study of lymph node stromal cell origin is described. The method involves the isolation of lymph nodes from newborn mice and embryonic fat pads, the generation of chimeric lymph node-fat pads, and their transfer under the kidney capsule of a host mouse.

The stroma is a key component of the lymph node structure and function. However, little is known about its origin, exact cellular composition and the ...

Isolation of Murine Lymph Node Stromal Cells

Secondary lymphoid organs including lymph nodes are composed of stromal cells that provide a structural environment for homeostasis, activation and differentiation of lymphocytes. Various stromal cell subsets have been identified by the expression of the adhesion molecule CD31 and glycoprotein podoplanin (gp38), T zone reticular cells or fibroblastic reticular cells, lymphatic endothelial cells, blood endothelial cells and FRC-like pericytes within the double negative cell population. For all populations different functions are described including, separation and lining of different compartments, attraction of and interaction with different cell types, filtration of the draining fluidics and contraction of the lymphatic vessels. In the last years, different groups have described an additional role of stromal cells in orchestrating and regulating cytotoxic T cell responses potentially dangerous for the host. 
Lymph nodes are complex structures with many different cell types and therefore require a appropriate procedure for isolation of the desired cell populations. Currently, protocols for the isolation of lymph node stromal cells rely on enzymatic digestion with varying incubation times; however, stromal cells and their surface molecules are sensitive to these enzymes, which results in loss of surface marker expression and cell death. Here a short enzymatic digestion protocol combined with automated mechanical disruption to obtain viable single cells suspension of lymph node stromal cells maintaining their surface molecule expression is proposed.

Isolation of lymph node stromal cells is a multistep procedure including enzymatic digestion and mechanical disaggregation to obtain fibroblastic reticular cells, lymphatic and blood endothelial cells. In the described procedure, a short digestion is combined with automated mechanical disaggregation to minimize surface marker degradation of viable lymph node stromal cells.

Secondary lymphoid organs including lymph nodes are composed of stromal cells that provide a structural environment for homeostasis, activation and ...

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 ...

Intracellular Staining and Flow Cytometry to Identify Lymphocyte Subsets within Murine Aorta, Kidney and Lymph Nodes in a Model of Hypertension

It is now well known that T lymphocytes play a critical role in the development of several cardiovascular diseases1,2,3,4,5. For example, studies from our group have shown that hypertension is associated with an excessive accumulation of T cells in the vessels and kidney during the development of experimental hypertension6. Once in these tissues, T cells produce several cytokines that affect both vascular and renal function leading to vasoconstriction and sodium and water retention1,2. To fully understand how T cells cause cardiovascular and renal diseases, it is important to be able to identify and quantify the specific T cell subsets present in these tissues. T cell subsets are defined by a combination of surface markers, the cytokines they secrete, and the transcription factors they express. The complexity of the T cell population makes flow cytometry and intracellular staining an invaluable technique to dissect the phenotypes of the lymphocytes present in tissues. Here, we provide a detailed protocol to identify the surface and intracellular markers (cytokines and transcription factors) in T cells isolated from murine kidney, aorta and aortic draining lymph nodes in a model of angiotensin II induced hypertension. The following steps are described in detail: isolation of the tissues, generation of the single cell suspensions, ex vivo stimulation, fixation, permeabilization and staining. In addition, several fundamental principles of flow cytometric analyses including choosing the proper controls and appropriate gating strategies are discussed.

This article provides detailed methodology to identify and quantify functional T lymphocyte subsets present within murine kidney, aorta and lymph nodes by intracellular staining and flow cytometry. The model of angiotensin II induced hypertension was chosen to explain, step-by-step, the procedures and fundamental principles of flow cytometry and intracellular staining.

It is now well known that T lymphocytes play a critical role in the development of several cardiovascular diseases1,2,3,4,5. For example, studies from our ...

Measurement of T Cell Alloreactivity Using Imaging Flow Cytometry

The measurement of immunological reactivity to donor antigens in transplant recipients is likely to be crucial for the successful reduction or withdrawal of immunosuppression. The mixed leukocyte reaction (MLR), limiting dilution assays, and trans-vivo delayed-type hypersensitivity (DTH) assay have all been applied to this question, but these methods have limited predictive ability and/or significant practical limitations that reduce their usefulness. Imaging flow cytometry is a technique that combines the multiparametric quantitative powers of flow cytometry with the imaging capabilities of fluorescent microscopy. We recently made use of an imaging flow cytometry approach to define the proportion of recipient T cells capable of forming mature immune synapses with donor antigen-presenting cells (APCs). Using a well-characterized mouse heart transplant model, we have shown that the frequency of in vitro immune synapses among T-APC membrane contact events strongly predicted allograft outcome in rejection, tolerance, and a situation where transplant survival depends on induced regulatory T cells. The frequency of T-APC contacts increased with T cells from mice during acute rejection and decreased with T cells from mice rendered unresponsive to alloantigen. The addition of regulatory T cells to the in vitro system reduced prolonged T-APC contacts. Critically, this effect was also seen with human polyclonally expanded, naturally occurring regulatory T cells, which are known to control the rejection of human tissues in humanized mouse models. Further development of this approach may allow for a deeper characterization of the alloreactive T-cell compartment in transplant recipients. In the future, further development and evaluation of this method using human cells may form the basis for assays used to select patients for immunosuppression minimization, and it can be used to measure the impact of tolerogenic therapies in the clinic.

This paper describes a method for measuring alloreactivity in a mixed population of T cells using imaging flow cytometry.

The measurement of immunological reactivity to donor antigens in transplant recipients is likely to be crucial for the successful reduction or withdrawal ...