Regulatory CD4 Research Articles

Regulatory CD8+ T cells are modulated in healthy and preeclampsia pregnancies

Regulatory CD8+ T cells are modulated in healthy and preeclampsia pregnancies

Immunotherapy targeting different immune compartments in combination with radiation therapy induces regression of resistant tumors

Radiation therapy (RT) increases tumor response to CTLA-4 inhibition (CTLA4i) in mice and in some patients, yet deep responses are rare. To identify rational combinations of immunotherapy to improve responses we use models of triple negative breast cancer highly resistant to immunotherapy in female mice. We find that CTLA4i promotes the expansion of CD4+ T helper cells, whereas RT enhances T cell clonality and enriches for CD8+ T cells with an exhausted phenotype. Combination therapy decreases regulatory CD4+ T cells and increases effector memory, early activation and precursor exhausted CD8+ T cells. A combined gene signature comprising these three CD8+ T cell clusters is associated with survival in patients. Here we show that targeting additional immune checkpoints expressed by intratumoral T cells, including PD1, is not effective, whereas CD40 agonist therapy recruits resistant tumors into responding to the combination of RT and CTLA4i, indicating the need to target different immune compartments.

Cytotoxic CD4 T cells in the mucosa and in cancer.

CD4 T cells were initially described as helper cells that promote either the cellular immune response (Th1 cells) or the humoral immune response (Th2 cells). Since then, a plethora of functionally distinct helper and regulatory CD4 T cell subsets have been described. CD4 T cells with cytotoxic function were first described in the setting of viral infections and autoimmunity, and more recently in cancer and gut dysbiosis. Regulatory CD4 T cell subsets such as Tregs and T-regulatory type 1 (Tr1) cells have also been shown to have cytotoxic potential. Indeed, Tr1 cells have been shown to be important for maintenance of stem cell niches in the bone marrow and the gut. This review will provide an overview of cytotoxic CD4 T cell development, and discuss the role of inflammatory and Tr1-like cytotoxic CD4 T cells in maintenance of intestinal stem cells and in anti-cancer immune responses.

Single-cell profiling reveals the trajectory of FOLR2-expressing tumor-associated macrophages to regulatory T cells in the progression of lung adenocarcinoma

An immunosuppressive microenvironment enriched with regulatory CD4+ T lymphocytes (Tregs) facilitates the progression of lung adenocarcinoma (LUAD). This study aims to investigate the cellular mechanism underlying the formation of the immunosuppressive microenvironment in LUAD. LUAD samples (n = 12) and normal lung samples (n = 3) were obtained from patients with different pathological stages of LUAD. Single-cell RNA sequencing was performed to classify cellular components and analyze the transcriptomes, including transcription factors/targets and chemokine ligands/receptors, followed by bioinformatics study such as pseudotime analysis. Myeloid cells and T cells were the most abundant cell types in tumors and normal lung tissues, while tumor-associated macrophage-folate receptor 2 (TAM-FOLR2) and CD4+ nuclear receptor subfamily 4 group A member 3 (NR4A3) exhibited sharp increases in invasive adenocarcinoma (IA). The enrichment of TAM-FOLR2 in IA might result from alveolar resident macrophage-resistin (ARM-RETN) transformation and recruitment of dendritic cells (DCs) and other TAMs, as evidenced by temporal trajectories and differential expression profiles of chemokine ligands/receptors versus those in the early stages of tumors. High expression of CCL17/19/22 was observed in IA as well as in DCs, along with the strong interaction of TAM-FOLR2 with DCs. The results of pseudotime analysis suggested that CD4+NR4A3 might potentially convert to CD4+FOXP3, further supported by the high expression of NR4A3 target genes in CD4+FOXP3 cells. This study provides a single-cell transcriptome atlas from preinvasive to invasive LUAD and reveals a potential ARM-RETN/TAM-FOLR2/DCs/CD4+NR4A3/CD4+FOXP3 trajectory in shaping the immune suppressive microenvironment along the pathogenesis of LUAD.

Regulatory T Cell Biomarkers Identify Patients at Risk of Developing Acute Cellular Rejection in the First Year Following Heart Transplantation.

Acute cellular rejection (ACR), an alloimmune response involving CD4+ and CD8+ T cells, occurs in up to 20% of patients within the first year following heart transplantation. The balance between a conventional versus regulatory CD4+ T cell alloimmune response is believed to contribute to developing ACR. Therefore, tracking these cells may elucidate whether changes in these cell populations could signal ACR risk. We used a CD4+ T cell gene signature (TGS) panel that tracks CD4+ conventional T cells (Tconv) and regulatory T cells (Treg) on longitudinal samples from 94 adult heart transplant recipients. We evaluated combined diagnostic performance of the TGS panel with a previously developed biomarker panel for ACR diagnosis, HEARTBiT, while also investigating TGS' prognostic utility. Compared with nonrejection samples, rejection samples showed decreased Treg- and increased Tconv-gene expression. The TGS panel was able to discriminate between ACR and nonrejection samples and, when combined with HEARTBiT, showed improved specificity compared with either model alone. Furthermore, the increased risk of ACR in the TGS model was associated with lower expression of Treg genes in patients who later developed ACR. Reduced Treg gene expression was positively associated with younger recipient age and higher intrapatient tacrolimus variability. We demonstrated that expression of genes associated with CD4+ Tconv and Treg could identify patients at risk of ACR. In our post hoc analysis, complementing HEARTBiT with TGS resulted in an improved classification of ACR. Our study suggests that HEARTBiT and TGS may serve as useful tools for further research and test development.

Cross-reactivity of T cell-specific antibodies in the bank vole (Myodes glareolus)

The bank vole is a common Cricetidae rodent that is a reservoir of several zoonotic pathogens and an emerging model in eco-immunology. Here, we add to a developing immunological toolkit for this species by testing the cross-reactivity of commercially available monoclonal antibodies (mAbs) to the bank vole lymphocyte differentiation molecules and a transcription factor. We show that a combination of mAbs against CD4, CD3, and Foxp3 allows flow cytometric distinction of the main subsets of T cells: putative helper CD4+, cytotoxic CD8+ (as CD3+CD4-) and regulatory CD4+Foxp3+. We also provide a comparative analysis of amino acid sequences of CD4, CD8αβ, CD3εγδ and Foxp3 molecules for a number of commonly studied Cricetidae rodents and discuss mAb cross-reactivity patterns reported so far in this rodent family. We found that in case of mAbs targeting the extracellular portions of commonly used T cell markers, sequence similarity is a poor prognostic of cross-reactivity. Use of more conserved, intracellular molecules or molecule fragments is a more reliable approach in non-model species, but the necessity of cell fixation limit its application in, e.g. functional studies.

Pparα knockout in mice increases the Th17 development by facilitating the IKKα/RORγt and IKKα/Foxp3 complexes

The helper CD4+ T cell-type 17 (Th17) cells and regulatory CD4+ T cells (Tregs) are balanced through numerous molecular regulators, particularly metabolic factors, and their alteration causes immune dysregulation. Herein, we report that peroxisome proliferator of activated receptor-alpha (Pparα), a lipid metabolism regulator, suppresses Th17 differentiation. We demonstrated that Pparα ablation improves Th17 and pro-Th17 factor HIF-1α by enhancing the expression and nuclear localization of NFκB-activator IκB kinase-alpha (IKKα). Unexpectedly, we found that IKKα directly interacts with RORγt and enhances the expression of Il17a gene. Meanwhile, IKKα also interacts with Foxp3, leading to the post-translational regulation of Foxp3 by elevating its proteasomal degradation, and influencing Th17 development. Pparα deficiency leads to enhanced Th17 development in vivo and is associated with enhanced pathology in a murine experimental autoimmune encephalomyelitis (EAE) model. Overall, our data indicate that Pparα may serve as a potential therapeutic target for autoimmune and inflammatory diseases.

The prognostic and predictive role of tumor-infiltrating lymphocytes (FoxP3 + and CD8 +) and tumor-associated macrophages in early HER2 + breast cancer

PurposeIn HER2-positive (HER2 +) breast cancer, tumor-infiltrating lymphocytes (TILs) and tumor-associated macrophages (TAMs) may influence the efficacy of the HER2-antibody trastuzumab and the patient’s outcome. In this HER2 + patient cohort, our aim was to study the numbers of FoxP3 + regulatory TILs and CD8 + cytotoxic TILs, their correlations with CD68 + and CD163 + TAMs, and the prognostic and predictive value of the studied factors.MethodsWe evaluated 139 non-metastatic HER2 + breast cancer patients operated between 2001 and 2008. The FoxP3+TIL count (FoxP3+TILs) was assessed using the hotspot method, and the CD8 + TIL count (CD8+mTILs) utilizing a digital image analysis from invasive margin areas. The ratios between CD8+mTILs and FoxP3+TILs as well as CD8+mTILs and TAMs were calculated.ResultsFoxP3 + TILs and CD8 + mTILs correlated positively with each other (p<0.001). FoxP3+TILs had a positive correlation with CD68+and CD163+TAMs (p≤0.038), while CD8 + mTILs correlated only with CD68+TAMs (p<0.001). In the HER2 + and hormone receptor-positive Luminal B subgroup, high numbers of FoxP3+TILs were associated with shorter disease-free survival (DFS) (54% vs. 79%, p = 0.040). The benefit from adjuvant trastuzumab was extremely significant among patients with a high CD8 + mTILs/CD68 + TAMs ratio, with overall survival (OS) 84% vs. 33% (p = 0.003) and breast cancer-specific survival (BCSS) 88% vs. 48% (p = 0.009) among patients treated with or without trastuzumab, respectively.ConclusionIn the HER2 + Luminal B subgroup, high FoxP3 + TILs were associated with shorter DFS. A high CD8 + mTILs/CD68 + TAMs ratio seems to associate with impressive efficacy of trastuzumab.

Effects of Oral Cannabinoids on Systemic Inflammation and Viral Reservoir Markers in People with HIV on Antiretroviral Therapy: Results of the CTN PT028 Pilot Clinical Trial.

Chronic HIV infection is characterized by persistent inflammation despite antiretroviral therapy (ART). Cannabinoids may help reduce systemic inflammation in people with HIV (PWH). To assess the effects of oral cannabinoids during HIV, ten PWH on ART were randomized (n = 5/group) to increasing doses of oral Δ9-tetrahydrocannabinol (THC): cannabidiol (CBD) combination (2.5:2.5-15:15 mg/day) capsules or CBD-only (200-800 mg/day) capsules for 12 weeks. Blood specimens were collected prospectively 7-21 days prior to treatment initiation and at weeks 0 to 14. Plasma cytokine levels were determined via Luminex and ELISA. Immune cell subsets were characterized by flow cytometry. HIV DNA/RNA were measured in circulating CD4 T-cells and sperm by ultra-sensitive qPCR. Results from both arms were combined for statistical analysis. Plasma levels of IFN-γ, IL-1β, sTNFRII, and REG-3α were significantly reduced at the end of treatment (p ˂ 0.05). A significant decrease in frequencies of PD1+ memory CD4 T-cells, CD73+ regulatory CD4 T-cells, and M-DC8+ intermediate monocytes was also observed (p ˂ 0.05), along with a transient decrease in CD28-CD57+ senescent CD4 and CD8 T-cells. Ki-67+ CD4 T-cells, CCR2+ non-classical monocytes, and myeloid dendritic cells increased over time (p ˂ 0.05). There were no significant changes in other inflammatory markers or HIV DNA/RNA levels. These findings can guide future large clinical trials investigating cannabinoid anti-inflammatory properties.

Liposomes loaded with vitamin D3 induce regulatory circuits in human dendritic cells.

Nanomedicine provides a promising platform for manipulating dendritic cells (DCs) and the ensuing adaptive immune response. For the induction of regulatory responses, DCs can be targeted in vivo with nanoparticles incorporating tolerogenic adjuvants and auto-antigens or allergens. Here, we investigated the tolerogenic effect of different liposome formulations loaded with vitamin D3 (VD3). We extensively phenotyped monocyte-derived DCs (moDCs) and skin DCs and assessed DC-induced regulatory CD4+ T cells in coculture. Liposomal VD3 primed-moDCs induced the development of regulatory CD4+ T cells (Tregs) that inhibited bystander memory T cell proliferation. Induced Tregs were of the FoxP3+ CD127low phenotype, also expressing TIGIT. Additionally, liposome-VD3 primed moDCs inhibited the development of T helper 1 (Th1) and T helper 17 (Th17) cells. Skin injection of VD3 liposomes selectively stimulated the migration of CD14+ skin DCs. These results suggest that nanoparticulate VD3 is a tolerogenic tool for DC-mediated induction of regulatory T cell responses.

Regulation of CD8 T Cell Differentiation by the RNA-Binding Protein DDX5.

The RNA-binding protein DEAD-box protein 5 (DDX5) is a polyfunctional regulator of gene expression, but its role in CD8+ T cell biology has not been extensively investigated. In this study, we demonstrate that deletion of DDX5 in murine CD8+ T cells reduced the differentiation of terminal effector, effector memory T, and terminal effector memory cells while increasing the generation of central memory T cells, whereas forced expression of DDX5 elicited the opposite phenotype. DDX5-deficient CD8+ T cells exhibited increased expression of genes that promote central memory T cell differentiation, including Tcf7 and Eomes. Taken together, these findings reveal a role for DDX5 in regulating the differentiation of effector and memory CD8+ T cell subsets in response to microbial infection.

FRI-357 - Differential activation of regulatory CD4+ T cells via the JAK-STAT-pathway in Primary sclerosing cholangitis

FRI-357 - Differential activation of regulatory CD4+ T cells via the JAK-STAT-pathway in Primary sclerosing cholangitis

Interferon beta treatment is a potent and targeted epigenetic modifier in multiple sclerosis.

Multiple Sclerosis (MS) has a complex pathophysiology that involves genetic and environmental factors. DNA methylation (DNAm) is one epigenetic mechanism that can reversibly modulate gene expression. Cell specific DNAm changes have been associated with MS, and some MS therapies such as dimethyl fumarate can influence DNAm. Interferon Beta (IFNβ), was one of the first disease modifying therapies in multiple sclerosis (MS). However, how IFNβ reduces disease burden in MS is not fully understood and little is known about the precise effect of IFNβ treatment on methylation. The objective of this study was to determine the changes in DNAm associated with INFβ use, using methylation arrays and statistical deconvolutions on two separate datasets (total ntreated = 64, nuntreated = 285). We show that IFNβ treatment in people with MS modifies the methylation profile of interferon response genes in a strong, targeted, and reproducible manner. Using these identified methylation differences, we constructed a methylation treatment score (MTS) that is an accurate discriminator between untreated and treated patients (Area under the curve = 0.83). This MTS is time-sensitive and in consistent with previously identified IFNβ treatment therapeutic lag. This suggests that methylation changes are required for treatment efficacy. Overrepresentation analysis found that IFNβ treatment recruits the endogenous anti-viral molecular machinery. Finally, statistical deconvolution revealed that dendritic cells and regulatory CD4+ T cells were most affected by IFNβ induced methylation changes. In conclusion, our study shows that IFNβ treatment is a potent and targeted epigenetic modifier in multiple sclerosis.

Variation in CD8 T cell IFNγ differentiation to strains of Toxoplasma gondii is characterized by small effect QTLs with contribution from ROP16.

Toxoplasma gondii induces a strong CD8 T cell response characterized by the secretion of IFNγ that promotes host survival during infection. The initiation of CD8 T cell IFNγ responses in vitro differs widely between clonal lineage strains of T. gondii, in which type I strains are low inducers, while types II and III strains are high inducers. We hypothesized this phenotype is due to a polymorphic "Regulator Of CD8 T cell Response" (ROCTR). Therefore, we screened F1 progeny from genetic crosses between the clonal lineage strains to identify ROCTR. Naïve antigen-specific CD8 T cells (T57) isolated from transnuclear mice, which are specific for the endogenous and vacuolar TGD057 antigen, were measured for their ability to become activated, transcribe Ifng and produce IFNγ in response to T. gondii infected macrophages. Genetic mapping returned four non-interacting quantitative trait loci (QTL) with small effect on T. gondii chromosomes (chr) VIIb-VIII, X and XII. These loci encompass multiple gene candidates highlighted by ROP16 (chrVIIb-VIII), GRA35 (chrX), TgNSM (chrX), and a pair of uncharacterized NTPases (chrXII), whose locus we report to be significantly truncated in the type I RH background. Although none of the chromosome X and XII candidates bore evidence for regulating CD8 T cell IFNγ responses, type I variants of ROP16 lowered Ifng transcription early after T cell activation. During our search for ROCTR, we also noted the parasitophorous vacuole membrane (PVM) targeting factor for dense granules (GRAs), GRA43, repressed the response suggesting PVM-associated GRAs are important for CD8 T cell activation. Furthermore, RIPK3 expression in macrophages was an absolute requirement for CD8 T cell IFNγ differentiation implicating the necroptosis pathway in T cell immunity to T. gondii. Collectively, our data suggest that while CD8 T cell IFNγ production to T. gondii strains vary dramatically, it is not controlled by a single polymorphism with strong effect. However, early in the differentiation process, polymorphisms in ROP16 can regulate commitment of responding CD8 T cells to IFNγ production which may have bearing on immunity to T. gondii.

Intrauterine activation of the fetal immune system in response to maternal COVID-19

Introduction. During pregnancy COVID-19 poses a serious threat to both maternal health and health of paired unborn child. Pregnant women have a high probability of complications due to respiratory viral infections followed by developing critical conditions caused by physiologically altered immune and cardiopulmonary systems. However, asymptomatic COVID-19 in pregnant women may be accompanied by fetal inflammatory response syndrome (FIRS) that results in unfavorable sequelae for neonatal life and health.Aim: to assess a fetal inflammatory response resulting from maternal COVID-19 in pregnancy.Materials and Мethods. A prospective randomized comparative study involving 92 pregnant women was carried out. The main group included 62 pregnant COVID-19 convalescent women: subgroup 1 consisted of 30 pregnant women found to be positive for SARS-CoV-2 by using polymerase chain reaction (PCR) 4–6 weeks before delivery; subgroup 2 – 32 pregnant women with SARS-CoV-2 detected by PCR earlier during pregnancy. The control group enrolled 30 healthy pregnant women. The level of circulating cytokines – interleukins (IL) IL-1α, IL-6, IL-8, IL-10, granulocyte-macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), macrophage inflammatory protein-1β (MIP-1β), C-X-C motif chemokine ligand 10 (CXCL-10) and cell markers (CD86, CD80, CD4, CD25, CD25, CCR7) were analyzed. In addition, all neonates underwent thymus gland ultrasound screening.Results. Cord blood dendritic cells from neonates born to mothers in subgroup 1 vs. control group showed a significantly upregulated expression of CD80 and CD86 (p = 0.023). Moreover, such cord blood samples in subgroup 1 were found to have increased percentage of CD4+, CCR7+ T cells paralleled with decreased proportion of naive CD4+ T cells as compared with control group (p = 0.016). It was found that count of maternal regulatory CD4+CD25+Foxp3+ T cells (Treg) did not differ significantly, whereas Treg cell functional activity in mothers with severe COVID-19 (subgroup 2) was significantly suppressed. Significantly higher level of neonatal proinflammatory cytokines and chemokines was detected in subgroup 1 vs. control group (p &lt; 0.05). However, the cytokines level in maternal peripheral blood samples in main and control groups upon delivery was changed insignificantly. SARS-CoV-2-positive pregnant women showed a strong antigen-specific T cell response. A reduced thymus size was found in neonates born to paired COVID-19 mothers.Conclusion. Fetal inflammatory response syndrome occurs upon COVID-19, which is characterized by activated fetal immune system and increased production of pro-inflammatory cytokines. The disease severity in pregnant women has no correlation with FIRS intensity during neonatal period and can vary from minimally altered laboratory parameters to developing sequelae at organ and body system levels.

Dietary protein shapes the profile and repertoire of intestinal CD4+ T cells.

The intestinal immune system must tolerate food antigens to avoid allergy, a process requiring CD4+ T cells. Combining antigenically defined diets with gnotobiotic models, we show that food and microbiota distinctly influence the profile and T cell receptor repertoire of intestinal CD4+ T cells. Independent of the microbiota, dietary proteins contributed to accumulation and clonal selection of antigen-experienced CD4+ T cells at the intestinal epithelium, imprinting a tissue-specialized transcriptional program including cytotoxic genes on both conventional and regulatory CD4+ T cells (Tregs). This steady state CD4+ T cell response to food was disrupted by inflammatory challenge, and protection against food allergy in this context was associated with Treg clonal expansion and decreased proinflammatory gene expression. Finally, we identified both steady-state epithelium-adapted CD4+ T cells and tolerance-induced Tregs that recognize dietary antigens, suggesting that both cell types may be critical for preventing inappropriate immune responses to food.

Interaction gene set between osteoclasts and regulatory CD4+ T cells can accurately predict the prognosis of patients with osteosarcoma.

Osteoclasts (OCs) and regulatory CD4+ T cells (CD4+ Tregs) are important components in the tumor microenvironment (TME) of osteosarcoma. In this study, we collected six osteosarcoma samples from our previous study (GSE162454). We also integrated a public database (GSE152048), which included single cell sequencing data of 11 osteosarcoma patients. We obtained 138,192 cells and then successfully identified OCs and CD4+ Tregs. Based on the interaction gene set between OCs and CD4+ Tregs, patients from GSE21257 were distinguished into two clusters by consensus clustering analysis. Both the tumor immune microenvironment and survival prognosis between the two clusters were significantly different. Subsequently, five model genes were identified by protein-protein interaction network based on differentially upregulated genes of cluster 2. Quantitative RT-PCR was used to detect their expression in human osteoblast and osteosarcoma cells. A prognostic model was successfully established using these five genes. Kaplan-Meier survival analysis found that patients in the high-risk group had worse survival (p = 0.029). Therefore, our study first found that cell-cell communication between OCs and CD4+ Tregs significantly alters TME and is connected to poor prognosis of OS. The model we constructed can accurately predict prognosis for osteosarcoma patients.

Interferon-lambda modulates dendritic cell IL-10 production and CD8 T cell immunity during influenza A virus infection

Abstract Influenza A virus (IAV) infection remains a major global health burden, requiring development of novel strategies to limit infection and drive durable protective immunity. Type III interferon (IFN), IFN-lambda, plays an important role in regulating IAV infection and immunity, but it’s contribution to regulating adaptive immunity remains less understood. Our previous research found mice lacking the IFN-lambda receptor (Ifnlr1−/−) are more susceptible to heterosubtypic rechallenge with influenza A virus. Ifnlr1−/−mice also have reduced effector and memory IAV-specific CD8 T cells compared to WT, highlighting a unique role for IFN-lambda in regulating protective CD8 T cell immunity against IAV. However, this defect in the CD8 T cell response was not T cell-intrinsic, but rather due to aberrant dendritic cell (DC) function in the absence of IFN-lambda signaling. RNA-Seq analysis of DC from the draining lymph nodes of mice following IAV infection revealed enhancement of an immunosuppressive network containing IL-10 in Ifnlr1−/−not present in WT. We hypothesize that IFN-lambda suppresses IL-10, playing a crucial role in regulation of protective CD8 T cell responses against IAV. Our results demonstrate IL-10 production is increased in bone marrow-derived DC (BMDC) in vitro and CD103 +DC in vivo following IAV infection in Ifnlr1−/−compared to WT. Ongoing experiments will unravel the contribution of IFN-lambda regulated IL-10 in regulation of CD8 T cell responses during IAV infection in vivo. Overall, understanding the mechanisms by which IFN-lambda signaling regulates DC function and protective CD8 T cell immunity will inform therapeutic potential of this cytokine during respiratory virus infection. Supported by NIH grant K22 AI146141

Gm2a as a novel regulator of CD8 +T cell threshold of activation in transplantation

Abstract Transplant patients must remain on toxic immunosuppression for life, underscoring the need to identify immunotherapeutic targets that may facilitate transplant tolerance. We recently showed that kidney transplant recipients that remained stable following withdrawal of mainstay immunosuppression exhibited increased levels of the glycosphingolipid-catabolizing protein Gm2a, specifically in CD8 +T cells, compared to patients who went on to reject their allografts. While the role of Gm2a in lysosomal glycosphingolipid degradation in neurons is well known, little is known about Gm2a function in the immune system. To investigate this, we performed skin graft surgery in WT vs Gm2a −/−mice. Results show that Gm2a deficiency significantly increased allograft rejection relative to WT counterparts. Moreover, adoptive transfer of donor-reactive WT vs. Gm2a −/−CD8 +T cells into WT hosts resulted in increased accumulation of donor-reactive T cells and accelerated allograft rejection in recipients of Gm2a −/−CD8 +T cells as compared to recipients of WT CD8 +T cells. This increased accumulation was likely due to increased proliferation, as in vitro studies revealed enhanced proliferation of CTV-labeled Gm2a −/−vs. WT CD8 +T cells. Interestingly, Gm2a −/−CD8 +T cells exhibited increased K b/SIINFEKL tetramer staining and sustained TCR expression following antigen stimulation compared to WT CD8 +T cells. Finally, Gm2a −/−CD8 +T cells exhibited increased responsiveness to low dose and low-affinity peptide compared to WT cells. In conclusion, these results identify Gm2a as a novel, CD8 +T cell-intrinsic regulator of the T cell activation threshold that directly impacts CD8 +T cell-mediated allograft rejection. Supported by grants from NIH (R01AI164716)

Transcription factor Nfil3 is a regulator of CD8 T cell differentiation in mouse Influenza A infection

Abstract After an acute respiratory infection is cleared, most T cells that controlled the infection die off. Tissue resident memory CD8 T cells (T RM) remain in the lung, poised to fight off a recurrent infection. These T RMhave large impacts on the survival and morbidity of subsequent infection. While many have studied this subset to understand what causes differentiation into this essential T cell subset, a master regulator of this phenotype remains elusive. To these ends, RNA and ATAC sequencing experiments of T RMwere conducted after viral clearance to investigate the existence of a master regulator. Transcription factor Nfil3 became a likely candidate after integrated omics analyses. Flow cytometry to fully characterize the levels of Nfil3 in all T cell subsets of the lung, spleen, and draining lymph node was conducted 7, 14, and 43 days post infection (dpi). At days 7 and 14 dpi, Nfil3 correlated with pre-T RMmarkers. At 43 dpi, Nfil3 was highest in T RMand lowest in central memory T cells. Finally, experiments were performed to investigate if Nfil3 played a causal role in T RMdevelopment or maintenance. T cells were transduced with Nfil3 overexpression constructs and adoptively transferred into mice, which were then infected. Notable changes in differentiation were observed between treatment and control. T cell proliferation was also affected ex vivoin a proliferation dye assay, implying that Nfil3 plays a role in the acute response. Finally, using a CD8-specific inducible floxout system, Nfil3 was floxed out during acute infection, recently post viral-clearance, and 6 weeks after during the memory phase to appreciate the effect on T cell differentiation. Overall, we argue Nfil3 plays a role in CD8 T cell differentiation in respiratory infections. This work was funded by a Program Project grant through the National Institutes of Health, National Institute of Allergy and Infectious Diseases P01-AI102851 and through the National Institutes of Health training grant T32GM007356-46 and the National Institutes of Health training grant T32HL066988-20.