The authors would like to thank Lirui Du for constructing the pCAGAdDU vector and Oliver Gorka for provision of the fixation protocol.

1. Cloning of a Gene of Interest into an Entry Vector
<ol>
	<li>Clone the gene of interest into an entry vector. PCR amplification of the gene followed by blunt-end ligation into a topoisomerase-coupled vector (e.g. pENTR/D-TOPO) or restriction enzyme-mediated cloning may be used for this procedure.</li>
</ol>
2. Transferring the Gene of Interest into the pCAGAdDu Destination Vector
<ol>
	<li>Transfer the gene of interest from the entry vector into the destination vector by LR recombination (e.g. Gateway LR Clonase II Enzyme Mix). This will create the adenoviral expression vector (Figure 1).</li>
	<li>Linearize 10 &mu;g of the adenoviral expression vector in a PacI restriction digest, precipitate the DNA and resuspend it in water at a concentration of 3 &mu;g per 100 &mu;l. Linearization liberates the viral inverted repeats (ITR), which are required for replication and encapsidation of the viral DNA into virus particles.</li>
</ol>
3. Generation of the Primary Virus Lysate
<ol>
	<li>Seed 1 x 105 HEK293A cells in 2 ml cell culture media (DMEM, 10% FBS, 5% PenStrep) in one well of a 6-well plate and incubate the cells for 6 - 14 hr at 37 &deg;C in a 10% CO2 incubator to allow them to adhere. Cells should then be at approximately 50% confluency.</li>
	<li>Lipofection: Transfer 6 &mu;l of jetPEI reagent into 94 &mu;l of 50 &mu;M NaCl, vortex briefly. Add the mixed solution to 100 &mu;l linearized adenovirus vector while vortexing and incubate this transfection mix for 15 - 30 min at room temperature.</li>
</ol>
Perform all following steps under the appropriate biosafety conditions for adenovirus infection!
<ol start="3">
	<li>Dispense the solution dropwise on the HEK293A cell-containing well and incubate the cells at 37 &deg;C and 10% CO2. When using a fluorescence marker, evaluate the transfection efficiency visually after 12 - 36 hr using an inverted fluorescence microscope. Add 0.5 ml of fresh medium every 3 days.</li>
	<li>Check every 2 - 3 days with a light or fluorescence microscope for cytopathic effects (CPE), which are areas with enlarged and rounded cells that start to detach. This is indicative of efficient virus generation. Upon occurrence of broader zones of CPE (Figure 3), it will take 24 - 72 hr before all cells are infected.</li>
	<li>When all cells show signs of CPE, but before an overall detachment of cells occurs, detach the cells by gentle pipetting and transfer cells with supernatant (SN, 3 - 5 ml) to a 15 ml polystyrene tube.</li>
	<li>Freeze the cells in the SN on dry ice for 15 - 20 min and thaw them quickly at 37 &deg;C afterwards to rupture the cells. Repeat this freeze-and-thaw-cycle (F/TC) two more times. Keep the primary virus lysate on ice for usage within a day or freeze it at -80 &deg;C for long-term storage. Any additional F/TC will reduce the virus titer by 30 - 50%.</li>
</ol>
4. Virus Amplification
<ol>
	<li>Seed and grow HEK293A cells to 90% confluence on a 14 cm tissue culture dish.</li>
	<li>Infect the cells with half of the primary virus lysate (1.5 - 2.5 ml) and incubate the cells for at least 36 hr. Nearly all cells should be infected then, which can be determined by fluorescence microscopy. For the re-amplification of an already amplified (i.e. more concentrated) virus stock, infect HEK293A at a multiplicity of infection (MOI) of 50 (see 6.3).</li>
	<li>Cells should be harvested when all of them show CPE but before detachment. With efficient virus production this state is reached within 48 hr after infection. (If it takes up to one week, consider another round of amplification by increasing the amount of adenovirus stock used for the infection described in 4.2.)</li>
	<li>Detach the cells by gentle pipetting and transfer cells and SN to a 50 ml polystyrene tube. Spin cells down at 300 x g for 10 min at 4 &deg;C.</li>
	<li>Remove the SN and resuspend the pellet in a suitable volume of medium or SN (ca. 1 ml).</li>
	<li>Perform 3 F/TC to disrupt the cells and centrifuge at 800 x g for 15 min at 4 &deg;C. Take off the SN that contains the virus particles (i.e. the concentrated virus lysate), and aliquot the virus lysate to store it at -80 &deg;C.</li>
</ol>
5. Virus Titer Determination
<ol>
	<li>Seed 105 A549 cells per well into 5 wells of a 12-well plate in 1 ml medium and let cells adhere for 6 hr.</li>
	<li>Use 1 &mu;l of concentrated adenovirus (thawed on ice) to perform a serial dilution in medium (1:5,000, 1:10,000, 1:50,000, 1:100,000) and add 10 &mu;l per well. Leave one well uninfected to adjust the gating in flow cytometry.</li>
	<li>After 36 hr, take off the SN, wash with PBS and detach cells (e.g. by trypsinization). For biohazard precautions, it is recommended to fix cells in 100 &mu;l 4% paraformaldehyde in PBS for 10 min at room temperature and wash with PBS one time.</li>
	<li>Perform a FACS analysis of infection marker expression. Plot '&mu;l viral lysate applied' against the absolute number of infected cells (Figure 4). Determine the linear range of infection and calculate the titer per ml of undiluted virus from the standard curve over the linear range using x = 1,000 &mu;l.</li>
</ol>
6. T Cell Infection
<ol>
	<li>Isolate naive/resting CD4 T cells from DO11.10 tg; CAR&Delta;1 tg mice using MACS (Naive CD4+ T Cell Isolation Kit II) or FACS sorting (CD4+ CD25- CD62L+ CD44-).</li>
	<li>For small-scale experiments, pipette an appropriate volume of viral lysate to achieve an MOI of 50 into one well of a 96-well round bottom plate.</li>
	<li>Add up to 4 x 105 T cells in a final infection volume of 50 &mu;l in T cell medium (RPMI1640, 10% FBS, 5% PenStrep, 5% NaPyruvate, 1x NEAA, 1x MEM Essential vitamin, 1x L-Glutamine, 1:250,000 Mercaptoethanol, 10 mM HEPES). 
	Example: 
	An MOI of 50 shall be used to infect 3 x 105 T cells; the viral titer is 3 x 109 ml-1 
	Virus volume = MOI x T cell number / viral titer = 50 x (3 x 105) / (3 x 109 ml-1) = 0.005 ml</li>
</ol>
Note: for infection of larger cell numbers, scale up using an MOI of 50 in an infection volume of 165 &mu;l per 106 naive T cells in a polystyrene tube with loose cup (up tp 3 ml per tube).
<ol start="4">
	<li>Incubate cells for 90 min at 37 &deg;C in a 5% CO2 incubator.</li>
	<li>Spin down cells at 300 x g for 5 min at room temperature, take off SN, resuspend in 200 &mu;l PBS. Centrifuge again and take off SN.</li>
</ol>
(Optional: the cells may be washed again to remove the virus more efficiently)
<ol start="6">
	<li>Resuspend cells in 200 &mu;l T cell medium without stimulating antibodies and without IL-2 or other cytokines and rest them for 40 hr at 37 &deg;C in a 5% CO2 incubator to allow expression of the gene of interest before activation.</li>
</ol>
7. T Cell Activation and Polarization
<ol>
	<li>Pipette a volume of anti-CD3- and anti-CD28-coupled beads that equals the cell number (e.g. 4 x 105) into a small reagent cup, add the 10-fold volume of PBS and put them on a magnet for 2 min. Take off the supernatant and resuspend the beads in 200 &mu;l polarizing medium (for Tregs: T cell medium + 1 ng/ml TGF&beta;, 100 U/ml IL-2).</li>
 </ol>
	Note: Cells can also be activated using tissue culture dishes coated with anti-CD28 and anti-CD3 antibodies, or in a DO11.10 T cell receptor-specific manner using irradiated BALB/c splenocytes pulsed with ovalbumin 323-339 peptide antigen.
 <ol start="2">
	<li>Centrifuge the rested cells as before, take off the SN and resuspend cells in 200 &mu;l polarizing medium containing anti-CD3- and anti-CD28-antibody-coupled beads. Incubate for 72 hr at 37 &deg;C in a 5% CO2 incubator without changing medium.</li>
</ol>
8. T Cell Fixation and Staining for Flow Cytometry
<ol>
	<li>Wash cells: Spin down cells at 300 x g for 5 min at room temperature, take off SN, resuspend in 200 &mu;l PBS. Centrifuge again and take off SN. Perform all following washing steps accordingly.</li>
	<li>Resuspend the cells in 100 &mu;l fixable dead cell staining solution and incubate for 30 min at 4 &deg;C.</li>
	<li>Wash cells, resuspend in 100 &mu;l PBS, add 100 &mu;l 4% paraformaldehyde in PBS, incubate 15 min at RT.</li>
	<li>Wash cells, resuspend them in 200 &mu;l ice-cold 70% methanol in PBS and incubate for 30 min on ice.</li>
</ol>
Note: Cells can be treated from now on without biohazard precaution!
<ol start="5">	
 <li>Prepare 60 &mu;l master-mix of 60 &mu;l PBS + 10 &mu;g/ml Fc-block (anti-FCR3 to block unspecific binding). Wash cells, resuspend them in 40 &mu;l of PBS + anti-FCR3 and incubate 15 min at RT.</li>
	<li>Add 20 &mu;l of PBS + anti-FCR3 containing 1 &mu;g PE-coupled anti-Foxp3 antibody, mix well and incubate at 4 &deg;C over night.</li>
	<li>Wash cells twice in PBS and analyze cells on a flow cytometer.</li>
</ol>

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The authors declare no conflict of interest.

Virus Generation and Titration
For optimal transfection results, the quality and amount of linearized vector appear most important. We did not observe negative effects on primary lysate production from an initial overgrowth of the culture since the infection will quickly proceed once efficient virus production occurs. However, virus production by HEK293A cells can be affected by long inserts that decrease the efficiency. Some open reading frames were actually found to interfere with virus product...

Tregs are crucial to maintain immune tolerance and to dampen overshooting immune responses. Tregs suppress bystander T cell activation. Consequently, ablation of Tregs leads to fatal autoimmunity and self-destruction driven by activated T cells1. Tregs develop in the thymus during negative selection of CD4 single-positive precursors, but they can also differentiate in the periphery from naive CD4 T cells upon low-dose antigen stimulation with suboptimal co-stimulation 1,2. Thymic Tregs seem to suppress tissue autoimmunity against self-antigens, whereas peripheral Tregs have been implicated in providing tolerance in the gut or lung. These induced Tregs potently prevent T cell activation after recognition of foreign antigens in the mucosa, including environmental antigens from food and air, commensal bacteria, and allergens 3,4. In addition, Tregs are crucial to establish maternal tolerance to fetal peptides 5 and to prevent graft-versus-host disease 6. At the same time, Tregs also mediate unwanted effects by attenuating immune surveillance of tumor cells 7,8. The hallmark feature of Tregs is the expression of the subset-specifying transcription factor Foxp3, a fork-head domain-containing transcription factor that is necessary and sufficient to confer Treg function 9,10. Some signaling pathways that can induce Foxp3 expression are known. However, the molecular processes that control, regulate, or modulate Treg differentiation in response to T cell receptor triggering are less well understood.
Tregs can very effectively be induced in vitro through the stimulation of naive CD4 T cells with anti-CD3 and anti-CD28 antibodies in the presence of TGF&beta; and IL-2 11. As the emerging Tregs are functional in vivo, the manipulation of molecules that promote Treg differentiation bears enormous potential for future therapies, for example, the treatment of asthma, Crohns disease, and transplantation 11,12. Conversely, therapeutic modulation of molecules to block Treg differentiation may provide benefit in future approaches of combined treatment of tumor patients.
In vitro differentiation assays have been instrumental for the description of molecular changes that are associated with T cell subset differentiation. At the moment, experimental attempts to search or screen for gene products that control T cell differentiation are hampered by the fact that the most common methods of ectopic gene expression fail in naive T cells. For example, electroporation and retroviral transduction are only effective in activated T cells. In contrast to initial expectations, lentiviral transduction, which is typically effective in resting cells, requires pre-activation of naive T cells by cytokines13. Furthermore, the transfer of cDNA or mRNA during electroporation involves depolarization of the plasma membrane, which itself confers features of T cell activation and may even mobilize Ca2+ signaling and activate NFAT proteins (unpublished observation and ref. 14). Similarly, for retroviral transduction, the naive T cells have to be activated for 18 - 40 hr. During this time, the breakdown of the nuclear membrane in the course of cell division occurs and allows for the subsequent genomic integration of the retroviral vector 15. These methods are therefore not able to address the early molecular regulation of initial T cell encounter with antigen, which is the decisive phase of helper T cell differentiation.
Adenoviral transduction is known to confer transient ectopic gene expression in a number of human cell types that express the human Coxsackie adenovirus receptor (CAR). It proceeds without requirement for cell activation or cell-cycle progression. The surface expression of CAR is essential for efficient virus attachment and internalization, and transgenic expression of the truncated version CAR&Delta;1 under a T cell-specific promoter was found to render mouse thymocytes and T cells susceptible to adenoviral infection 16. Importantly, the transgene does not alter thymocyte development or in vitro differentiation of naive CD4 T cells into different subsets (data not shown; ref. 17). Adenovirus-mediated transduction of T cells was previously used for overexpression 17,18 and knock-down approaches 19,20. The transgenic T cells can be purified from commercially available DO11.10 tg; CAR&Delta;1 tg (Taconic, Inc. and ref. 17). Importantly, adenoviral transduction allows high expression of a gene of interest in naive T cells without inducing obvious signs of activation. The T cells remain naive (CD44low, CD62Lhigh) and resting (CD25-, CD69-) after infection and can be activated and differentiated into Treg similar to non-infected cells.
 
Production of recombinant adenoviruses can be achieved after transfection of HEK293A cells with adenoviral plasmids (Figure 1). These plasmids typically contain the human type 5 adenovirus genome with E1 and E3 genes deleted to render recombinant adenoviruses replication-incompetent 21. HEK293A cells complement replication deficiency as they have been immortalized through stable integration of sheared adenovirus 22. Since adenoviral vectors are large (~40 kb) and consequently not well suited for traditional restriction enzyme-mediated cloning, we employed the Gateway system. The gene of interest is initially cloned into a smaller entry vector, from which it can be easily transferred into the adenoviral destination vector via lambda recombination reaction (LR) 23. We constructed the pCAGAdDu vector by combining the CAG promoter (chicken actin promoter and CMV enhancer) with an expression cassette containing LR sites flanking the procaryotic ccdB selection marker 24 . This expression cassette is fused to an internal ribosome entry site (IRES) element that allows coexpression of the eukaryotic infection marker enhanced green fluorescent protein (eGFP), which is fused to a sequence containing the bovine growth hormone poly(A)-signal. We chose the CAG cis-regulatory sequences, since the prototypic CMV promoter was found to be highly activation-dependent and therefore unfavorable for gene expression in naive T cells.
Here, we provide a protocol for efficient in vitro Treg differentiation and a method to transduce naive CD4 T cells without activation (Figure 2). The method enables ectopic gene expression or knock down preceding CD4 T cell differentiation at the naive state. It allows testing the effect of an overexpressed gene of interest during early signaling events upon initial TCR stimulation until T cell subset commitment. Our validation experiments also provide the basis to establish similar adenovirus application in the differentiation of other T cell subsets such as Th1, Th2, Th9, Th17, Th22, or Tfh cells.

<table border="1">
	<tbody>
		<tr>
			<td>Name of the reagent</td>
			<td>Company</td>
			<td>Catalogue number</td>
		</tr>
		<tr>
			<td>pENTR/D-TOPO Cloning Kit</td>
			<td>Invitrogen</td>
			<td>K240020</td>
		</tr>
		<tr>
			<td>Gateway LR Clonase II Enzyme mix</td>
			<td>Invitrogen</td>
			<td>11791020</td>
		</tr>
		<tr>
			<td>PacI</td>
			<td>New England Biolabs</td>
			<td>R057S</td>
		</tr>
		<tr>
			<td>jetPEI</td>
			<td>Polyplus-transfection</td>
			<td>101-10N</td>
		</tr>
		<tr>
			<td>HEK293A Cell Line</td>
			<td>Invitrogen</td>
			<td>R705-07</td>
		</tr>
		<tr>
			<td>A549</td>
			<td>ATCC</td>
			<td>CCL-185</td>
		</tr>
		<tr>
			<td>6-well plates</td>
			<td>BD Falcon</td>
			<td>353046</td>
		</tr>
		<tr>
			<td>14 cm tissue culture dish</td>
			<td>Nunc</td>
			<td>168381</td>
		</tr>
		<tr>
			<td>BALB/cJ-Tg(DO11.10)10Dlo Tg(CAR&Delta;1)1Jdgr</td>
			<td>Taconic Farms</td>
			<td>Model Nr. 4285</td>
		</tr>
		<tr>
			<td>Naive CD4+ T Cell Isolation Kit II</td>
			<td>Miltenyi Biotech</td>
			<td>130-094-131</td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Invitrogen</td>
			<td>41966-052</td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>PAN Biotech</td>
			<td>1502-P110704</td>
		</tr>
		<tr>
			<td>PenStrep</td>
			<td>Invitrogen</td>
			<td>15140-122</td>
		</tr>
		<tr>
			<td>RPMI 1640</td>
			<td>Lonza</td>
			<td>BE12-167F</td>
		</tr>
		<tr>
			<td>NaPyruvate</td>
			<td>Lonza</td>
			<td>BE13-115E</td>
		</tr>
		<tr>
			<td>NEAA 100x</td>
			<td>Lonza</td>
			<td>BE13-114E</td>
		</tr>
		<tr>
			<td>L-Glutamine</td>
			<td>Invitrogen</td>
			<td>25030</td>
		</tr>
		<tr>
			<td>HEPES Buffer Solution (1 M)</td>
			<td>Invitrogen</td>
			<td>15630-056</td>
		</tr>
		<tr>
			<td>&beta;-Mercaptoethanol</td>
			<td>Sigma-Aldrich</td>
			<td>M-7522</td>
		</tr>
		<tr>
			<td>MEM Essential vitamin mixture (100x)</td>
			<td>Lonza</td>
			<td>13-607C</td>
		</tr>
		<tr>
			<td>Dynabeads Mouse T-Activator CD3/CD28 for Cell Expansion and Activation</td>
			<td>Invitrogen</td>
			<td>114-56D</td>
		</tr>
		<tr>
			<td>Recombinant Human TGF-beta 1</td>
			<td>R&amp;D Systems</td>
			<td>240B</td>
		</tr>
		<tr>
			<td>Proleukin S (18 x 106IE)</td>
			<td>Novartis</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>LIVE/DEAD Fixable Blue Dead Cell Stain Kit</td>
			<td>Invitrogen</td>
			<td>L-23105</td>
		</tr>
		<tr>
			<td>Mouse BD Fc BlockT</td>
			<td>BD Pharmingen</td>
			<td>553141</td>
		</tr>
		<tr>
			<td>Anti-Mouse/Rat Foxp3 PE</td>
			<td>eBioscience</td>
			<td>12-5773-82</td>
		</tr>
		<tr>
			<td>Mmu-miR-155 TaqMan MicroRNA Assay</td>
			<td>Roche Applied Biosystems</td>
			<td>4427975</td>
		</tr>
		<tr>
			<td>LightCycler 480 Probes Master</td>
			<td>Roche Applied Biosystems</td>
			<td>04902343001</td>
		</tr>
		<tr>
			<td>TaqMan MicroRNA Reverse Transcription Kit</td>
			<td>Roche Applied Biosystems</td>
			<td>4366596</td>
		</tr>
	</tbody>
</table>

adenoviral transduction of naive cd4 t cells to study treg differentiation

Regulatory T cells (Tregs) are essential to provide immune tolerance to self as well as to certain foreign antigens. Tregs can be generated from naive CD4 T cells in vitro with TCR- and co-stimulation in the presence of TGF&beta; and IL-2. This bears enormous potential for future therapies, however, the molecules and signaling pathways that control differentiation are largely unknown.
Primary T cells can be manipulated through ectopic gene expression, but common methods fail to target the most important naive state of the T cell prior to primary antigen recognition. Here, we provide a protocol to express ectopic genes in naive CD4 T cells in vitro before inducing Treg differentiation. It applies transduction with the replication-deficient adenovirus and explains its generation and production. The adenovirus can take up large inserts (up to 7 kb) and can be equipped with promoters to achieve high and transient overexpression in T cells. It effectively transduces naive mouse T cells if they express a transgenic Coxsackie adenovirus receptor (CAR). Importantly, after infection the T cells remain naive (CD44low, CD62Lhigh) and resting (CD25-, CD69-) and can be activated and differentiated into Tregs similar to non-infected cells. Thus, this method enables manipulation of CD4 T cell differentiation from its very beginning. It ensures that ectopic gene expression is already in place when early signaling events of the initial TCR stimulation induces cellular changes that eventually lead into Treg differentiation.

Virus Production
For generation of high virus titers, the timing of HEK293A cell harvest in primary virus production or virus amplification is crucial. Representative fluorescent and phase contrast images with visual signs of virus production are shown in Figure 3. The CPE were observed 10 days after transfection of HEK293A cells with a control pCAGAdDu vector without insert. CPE are characterized by the appearance of areas with enlarged and round-up cells that start to detach an...

Watch this Scientific Journal Video about Adenoviral Transduction of Naive CD4 T Cells to Study Treg Differentiation at JoVE.com

Adenoviral Transduction of Naive CD4 T Cells to Study Treg Differentiation

Adenoviral gene transfer into naive CD4 T cells with transgenic expression of the Coxsackie adenovirus receptor enables the molecular analysis of regulatory T cell differentiation in vitro.

Regulatory T cells (Tregs) are essential to provide immune tolerance to self as well as to certain foreign antigens. Tregs can be generated from naive CD4 ...

adenoviral-transduction-naive-cd4-t-cells-to-study-treg

Research

JoVE Journal

Immunology and Infection

15.7K Views.  Helmholtz Zentrum München. Adenoviral gene transfer into naive CD4 T cells with transgenic expression of the Coxsackie adenovirus receptor enables the molecular analysis of regulatory T cell differentiation in vitro.

Video: Adenoviral Transduction of Naive CD4 T Cells to Study Treg Differentiation

Retroviral Transduction of T-cell Receptors in Mouse T-cells

T-cell receptors (TCRs) play a central role in the immune system. TCRs on T-cell surfaces can specifically recognize peptide antigens presented by antigen presenting cells (APCs)1. This recognition leads to the activation of T-cells and a series of functional outcomes (e.g. cytokine production, killing of the target cells). Understanding the functional role of TCRs is critical to harness the power of the immune system to treat a variety of immunology related diseases (e.g. cancer or autoimmunity).
It is convenient to study TCRs in mouse models, which can be accomplished in several ways. Making TCR transgenic mouse models is costly and time-consuming and currently there are only a limited number of them available2-4. Alternatively, mice with antigen-specific T-cells can be generated by bone marrow chimera. This method also takes several weeks and requires expertise5. Retroviral transduction of TCRs into in vitro activated mouse T-cells is a quick and relatively easy method to obtain T-cells of desired peptide-MHC specificity. Antigen-specific T-cells can be generated in one week and used in any downstream applications. Studying transduced T-cells also has direct application to human immunotherapy, as adoptive transfer of human T-cells transduced with antigen-specific TCRs is an emerging strategy for cancer treatment6.
Here we present a protocol to retrovirally transduce TCRs into in vitro activated mouse T-cells. Both human and mouse TCR genes can be used. Retroviruses carrying specific TCR genes are generated and used to infect mouse T-cells activated with anti-CD3 and anti-CD28 antibodies. After in vitro expansion, transduced T-cells are analyzed by flow cytometry.

We present a protocol to produce antigen-specific mouse T-cells using retroviral transduction

T-cell receptors (TCRs) play a central role in the immune system. TCRs on T-cell surfaces can specifically recognize peptide antigens presented by antigen ...

Isolation and Th17 Differentiation of Na&iuml;ve CD4 T Lymphocytes

Th17 cells are a distinct subset of T cells that have been found to produce interleukin 17 (IL-17), and differ in function from the other T cell subsets including Th1, Th2, and regulatory T cells. Th17 cells have emerged as a central culprit in overzealous inflammatory immune responses associated with many autoimmune disorders. In this method we purify T lymphocytes from the spleen and lymph nodes of C57BL/6 mice, and stimulate purified CD4+ T cells under control and Th17-inducing environments. The Th17-inducing environment includes stimulation in the presence of anti-CD3 and anti-CD28 antibodies, IL-6, and TGF-&#946;. After incubation for at least 72 hours and for up to five days at 37 &#176;C, cells are subsequently analyzed for the capability to produce IL-17 through flow cytometry, qPCR, and ELISAs. Th17 differentiated CD4+CD25- T cells can be utilized to further elucidate the role that Th17 cells play in the onset and progression of autoimmunity and host defense. Moreover, Th17 differentiation of CD4+CD25- lymphocytes from distinct murine knockout/disease models can contribute to our understanding of cell fate plasticity.

Isolation and Th17 Differentiation of Na&amp;#239;ve CD4 T Lymphocytes

With effector functions distinct from other T cell subsets, Th17 cells have been centrally implicated in inflammatory autoimmunity. This in vitro Th17 differentiation protocol provides a means to determine whether na&#239;ve CD4+ T lymphocytes can differentiate into Th17 cells, and to further examine their role in autoimmunity and host response.

Th17 cells are a distinct subset of T cells that have been found to produce interleukin 17 (IL-17), and differ in function from the other T cell subsets ...

Transplantation of Tail Skin to Study Allogeneic CD4 T Cell Responses in Mice

The study of T cell responses and their consequences during allo-antigen recognition requires a model that enables one to distinguish between donor and host T cells, to easily monitor the graft, and to adapt the system in order to answer different immunological questions. Medawar and colleagues established allogeneic tail-skin transplantation in mice in 1955. Since then, the skin transplantation model has been continuously modified and adapted to answer specific questions. The use of tail-skin renders this model easy to score for graft rejection, requires neither extensive preparation nor deep anesthesia, is applicable to animals of all genetic background, discourages ischemic necrosis, and permits chemical and biological intervention. 
In general, both CD4+ and CD8+ allogeneic T cells are responsible for the rejection of allografts since they recognize mismatched major histocompatibility antigens from different mouse strains. Several models have been described for activating allogeneic T cells in skin-transplanted mice. The identification of major histocompatibility complex (MHC) class I and II molecules in different mouse strains including C57BL/6 mice was an important step toward understanding and studying T cell-mediated alloresponses. In the tail-skin transplantation model described here, a three-point mutation (I-Abm12) in the antigen-presenting groove of the MHC-class II (I-Ab) molecule is sufficient to induce strong allogeneic CD4+ T cell activation in C57BL/6 mice. Skin grafts from I-Abm12 mice on C57BL/6 mice are rejected within 12-15 days, while syngeneic grafts are accepted for up to 100 days. The absence of T cells (CD3-/- and Rag2-/- mice) allows skin graft acceptance up to 100 days, which can be overcome by transferring 2 x 104 wild type or transgenic T cells. Adoptively transferred T cells proliferate and produce IFN-&#947; in I-Abm12-transplanted Rag2-/- mice.

Tail-skin transplantation is a powerful model for studying T cell-dependent rejection and tolerance induction during allogeneic immune responses in mice. The advantages of this protocol are minor invasive surgery, and ease of monitoring with no need to sacrifice the recipient mouse.

The study of T cell responses and their consequences during allo-antigen recognition requires a model that enables one to distinguish between donor 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&amp;#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 ...

Retroviral Transduction of Bone Marrow Progenitor Cells to Generate T-cell Receptor Retrogenic Mice

T cell receptor (TCR) signaling is essential in the development and differentiation of T cells in the thymus and periphery, respectively. The vast array of TCRs proves studying a specific antigenic response difficult. Therefore, TCR transgenic mice were made to study positive and negative selection in the thymus as well as peripheral T cell activation, proliferation and tolerance. However, relatively few TCR transgenic mice have been generated specific to any given antigen. Thus, studies involving TCRs of varying affinities for the same antigenic peptide have been lacking. The generation of a new TCR transgenic line can take six or more months. Additionally, any specific backcrosses can take an additional six months. In order to allow faster generation and screening of multiple TCRs, a protocol for retroviral transduction of bone marrow was established with stoichiometric expression of the TCR&#945; and TCR&#946; chains and the generation of retrogenic mice. Each retrogenic mouse is essentially a founder, virtually negating a founder effect, while the length of time to generate a TCR retrogenic is cut from six months to approximately six weeks. Here we present a rapid and flexible alternative to TCR transgenic mice that can be expressed on any chosen background with any particular TCR.

We present a rapid and flexible protocol for a single T cell receptor (TCR) retroviral-based in vivo expression system. Retroviral vectors are used to transduce bone marrow progenitor cells to study T cell development and function of a single TCR in vivo as an alternative to TCR transgenic mice.

T cell receptor (TCR) signaling is essential in the development and differentiation of T cells in the thymus and periphery, respectively.  The vast array ...

Retroviral Transduction of Helper T Cells as a Genetic Approach to Study Mechanisms Controlling their Differentiation and Function

Helper T cell development and function must be tightly regulated to induce an appropriate immune response that eliminates specific pathogens yet prevents autoimmunity. Many approaches involving different model organisms have been utilized to understand the mechanisms controlling helper T cell development and function. However, studies using mouse models have proven to be highly informative due to the availability of genetic, cellular, and biochemical systems. One genetic approach in mice used by many labs involves retroviral transduction of primary helper T cells. This is a powerful approach due to its relative ease, making it accessible to almost any laboratory with basic skills in molecular biology and immunology. Therefore, multiple genes in wild type or mutant forms can readily be tested for function in helper T cells to understand their importance and mechanisms of action. We have optimized this approach and describe here the protocols for production of high titer retroviruses, isolation of primary murine helper T cells, and their transduction by retroviruses and differentiation toward the different helper subsets. Finally, the use of this approach is described in uncovering mechanisms utilized by microRNAs (miRNAs) to regulate pathways controlling helper T cell development and function.

Many experimental systems have been utilized to understand the mechanisms regulating T cell development and function in an immune response. Here a genetic approach using retroviral transduction is described, which is economic, time efficient, and most importantly, highly informative in identifying regulatory pathways.

Helper T cell development and function must be tightly regulated to induce an appropriate immune response that eliminates specific pathogens yet prevents ...

In Vitro Differentiation of Human CD4+FOXP3+ Induced Regulatory T Cells (iTregs) from Na&#239;ve CD4+ T Cells Using a TGF-&#946;-containing Protocol

Regulatory T cells (Tregs) are an integral part of peripheral tolerance, suppressing immune reactions against self-structures and thus preventing autoimmune diseases. Clinical approaches to adoptively transfer Tregs, or to deplete Tregs in cancer, are underway with promising first outcomes. 
Because the number of naturally occurring Tregs (nTregs) is very limited, studying certain Treg features using in vitro induced Tregs (iTregs) can be advantageous. To date, the best although not absolutely specific protein marker to delineate Tregs is the transcription factor FOXP3. Despite the importance of Tregs including non-redundant roles of peripherally induced Tregs, the protocols to generate iTregs are currently controversial, particularly for human cells. This protocol therefore describes the in vitro differentiation of human CD4+FOXP3+ iTregs from human na&#239;ve T cells using a range of Treg-inducing factors (TGF-&#946; plus IL-2 only, or their combination with retinoic acid, rapamycin or butyrate) in parallel. It also describes the phenotyping of these cells by flow cytometry and qRT-PCR. 
These protocols result in reproducible expression of FOXP3 and other Treg signature genes and enable the study of general FOXP3-regulatory mechanisms as well as protocol-specific effects to delineate the impact of certain factors. iTregs can be utilized to study various phenotypic aspects as well as molecular mechanisms of Treg induction. Detailed molecular studies are facilitated by relatively large cell numbers that can be obtained. 
A limitation for the application of iTregs is the relative instability of FOXP3 expression in these cells compared to nTregs. iTregs generated by these protocols can also be used for functional assays such as studying their suppressive function, in which iTregs induced by TGF-&#946; plus retinoic acid and rapamycin display superior suppressive activity. However, the suppressive capacity of iTregs can differ from nTregs and the use of appropriate controls is crucial.

&lt;em&gt;In Vitro&lt;/em&gt; Differentiation of Human CD4&lt;sup&gt;+&lt;/sup&gt;FOXP3&lt;sup&gt;+&lt;/sup&gt; Induced Regulatory T Cells (iTregs) from Na&amp;#239;ve CD4&lt;sup&gt;+&lt;/sup&gt; T Cells Using a TGF-&amp;#946;-containing Protocol

This protocol describes the reproducible generation and phenotyping of human induced regulatory T cells (iTregs) from na&#239;ve CD4+ T cells in vitro. Different protocols for FOXP3 induction allow for the study of specific iTreg phenotypes obtained with respective protocols.

Regulatory T cells (Tregs) are an integral part of peripheral tolerance, suppressing immune reactions against self-structures and thus preventing ...

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.

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

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 ...

Deciphering Early Follicular Helper T-Cell Commitment in Acute LCMV Infection

Accessing Early Differentiation of Virus-Specific Follicular Helper CD4+ T Cell in Acute LCMV-Infected Mice

Follicular Helper T (TFH) cells are perceived as an independent CD4+ T cell lineage that assists cognate B cells in producing high-affinity antibodies, thus establishing long-term humoral immunity. During acute viral infection, the fate commitment of virus-specific TFH cells is determined in the early infection phase, and investigations of the early-differentiated TFH cells are crucial in understanding T cell-dependent humoral immunity and optimizing vaccine design. In the study, using a mouse model of acute lymphocytic choriomeningitis virus (LCMV) infection and the TCR-transgenic SMARTA (SM) mouse with CD4+ T cells specifically recognizing LCMV glycoprotein epitope I-AbGP66-77, we described procedures to access the early fate commitment of virus-specific TFH cells based on flow cytometry stainings. Furthermore, by exploiting retroviral transduction of SM CD4+ T cells, methods to manipulate gene expression in early-differentiated virus-specific TFH cells are also provided. Hence, these methods will help in studies exploring the mechanism(s) underlying the early commitment of virus-specific TFH cells.

Author Spotlight: Elucidating the Pathways of TFH Cell Differentiation in Acute LCMV Challenges

The current study showcases protocols for assessing the early fate commitment of virus-specific TFH cells and manipulating gene expression in these cells.

Follicular Helper T (TFH) cells are perceived as an independent CD4+ T cell lineage that assists cognate B cells in producing high-affinity antibodies, ...

Th17 Cell Differentiation from Naive CD4&lt;sup&gt;+&lt;/sup&gt; T-Cells Using Flow Cytometry

In Vitro Differentiation of Naive CD4+ T Cells into Pathogenic Th17 Cells in Mouse

In vitro T cell differentiation techniques are essential for both functional and mechanistic investigations of CD4+ T cells. Pathogenic Th17 cells have been linked to a wide range of diseases in recent times, including multiple sclerosis (MS), rheumatoid arthritis, acute respiratory distress syndrome (ARDS), sepsis, and other autoimmune disorders. However, the currently known in vitro differentiation protocols have difficulty achieving high purity of pathogenic Th17 cells, with the induction efficiency often below 50%, which is a key challenge in in vitro experiments. In this protocol, we propose an enhanced in vitro culture and differentiation protocol for pathogenic Th17 cells, which is used to directly differentiate naive CD4+ T cells isolated from mouse spleens into pathogenic Th17 cells. This protocol provides detailed instructions on splenocyte isolation, purification of naive CD4+ T cells, and differentiation of pathogenic Th17 cells. Through this protocol, we can achieve a differentiation purity of approximately 90% for pathogenic Th17 cells, which meets the basic needs of many cellular experiments.

Author Spotlight: Achieving High-Purity In Vitro Differentiation of Th17 Cells Using Cytokine Concentration Modulation

This protocol describes the differentiation of na&#239;ve CD4+ T cells into pathogenic Th17 cells in vitro. Specifically, when combined with a multi-parameter flow cytometry-based approach, 90% purity of pathogenic Th17 cells can be obtained from na&#239;ve CD4+ T cells using this differentiation method.

In vitro T cell differentiation techniques are essential for both functional and mechanistic investigations of CD4+ T cells. Pathogenic Th17 cells have ...