Sarcoidosis and Airway Disease After Immune Checkpoint Inhibitor Therapy: Case Study and Review of the Literature

Pulmonary toxicity from immune checkpoint inhibitor therapy is typically a severe and potentially fatal complication, but these observations are driven by the most common toxicity, pneumonitis. Rarer pulmonary immune related adverse events, like airway disease and sarcoidosis, may have a more benign course. In this case report, we present a patient in whom therapy with the PD-1 inhibitor pembrolizumab resulted in severe eosinophilic asthma and sarcoidosis. This is the first case showing that anti-IL-5 inhibition may be safe in patients who develop eosinophilic asthma after ICI therapy. We further show that sarcoidosis does not necessarily require treatment cessation. This case highlights relevant nuances when clinicians face pulmonary toxicities other than pneumonitis.

Anaplastic transformation in thyroid cancer revealed by single cell transcriptomics

The deadliest anaplastic thyroid cancer (ATC) often transforms from indolent differentiated thyroid cancer (DTC); however, the complex intra-tumor transformation process is poorly understood. We investigated an anaplastic transformation model by dissecting both cell lineage and cell fate transitions using single cell transcriptomes and genetic alteration data from patients with different subtypes of thyroid cancer. The resulting spectrum of ATC transformation included stress-responsive DTC cells, inflammatory ATC cells (iATCs), mitotic-defective ATC cells and extended all the way to mesenchymal ATC cells (mATCs). Further, our analysis identified two important milestones: 1) a diploid stage, where iATC cells were diploids with inflammatory phenotypes, and 2) an aneuploid stage, where mATCs gained aneuploid genomes and mesenchymal phenotypes producing excessive collagens and collagen-interacting receptors. In parallel, cancer-associated-fibroblasts showed strong interactions among mesenchymal cell-types, macrophages shifted from M1 to M2 states, and T cells reprogrammed from cytotoxic to exhausted states, highlighting new therapeutic opportunities for ATC.

Abstract 3131: Anaplastic transformation model in thyroid cancer revealed by single cell lineage and fate analysis

The deadliest anaplastic thyroid cancer (ATC) often transforms from indolent differentiated thyroid cancer (DTC), however the complex intra-tumor transformation process is poorly understood. We investigated an anaplastic transformation model by dissecting both cell lineage and cell fate transitions using single cell transcriptomes and genetic alterations data of patients with different subtypes of thyroid cancer. The resulting model started from stress-responsive DTC cells to inflammatory ATC cells, to mitotic defective ATC cells and extended all the way to mesenchymal ATC cells. In parallel with tumor cell evolution, macrophages shifted from anti-tumor to tumor-promoting states and T cells reprogrammed from cytotoxic to exhausted states. Further, our analysis identified two important milestones: 1) diploid stage, where ATC cells were commonly diploids with non-RAS mutations and inflammatory phenotypes. 2) aneuploid stage, where ATC cells gained aneuploidy with frequent RAS mutations and mesenchymal phenotypes leading to the extreme lethal stage of ATC progression.

Citation Format: Lina Lu, Jennifer Rui Wang, Ying C. Henderson, Shanshan Bai, Jie Yang, Min Hu, Yuanqing Yan, Tuan M Tran, Jianzhuo Li, Cheng-Kai Shiau, Rachel Kieser, Xiao Zhao, Jiping Wang, Roza Nurieva, Michelle D. Williams, Maria E. Cabanillas, Ramona Dadu, Naifa Lamki Busaidy, Mark Zafereo, Nicholas Navin, Stephen Y. Lai, Ruli Gao. Anaplastic transformation model in thyroid cancer revealed by single cell lineage and fate analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3131.

Radiation therapy induces immunosenescence mediated by p90RSK

Radiation therapy (RT) to the chest increases the patients' risk of cardiovascular disease (CVD). A complete understanding of the mechanisms by which RT induces CVD could lead to specific preventive, therapeutic approaches. It is becoming evident that both genotoxic chemotherapy agents and radiation induce mitochondrial dysfunction and cellular senescence. Notably, one of the common phenotypes observed in cancer survivors is accelerated senescence, and immunosenescence is closely related to both cancer risk and CVD development. Therefore, suppression of immunosenescence can be an ideal target to prevent cancer treatment-induced CVD. However, the mechanism(s) by which cancer treatments induce immunosenescence are incompletely characterized. We isolated peripheral blood mononuclear cells (PBMCs) before and 3 months after RT from 16 thoracic cancer patients. We characterized human immune cell lineages and markers of senescence, DNA damage response (DDR), efferocytosis, and determinants of clonal hematopoiesis of indeterminant potential (CHIP), using mass cytometry (CyTOF). We found that the frequency of the B cell subtype was decreased after RT. Unsupervised clustering of the CyTOF data identified 138 functional subsets of PBMCs. Compared with baseline, RT increased TBX21 (T-bet) expression in the largest B cell subset of Ki67-/DNMT3a+naïve B cells, and T-bet expression was correlated with phosphorylation of p90RSK expression. CD38 expression was also increased in naïve B cells (CD27-) and CD8+ effector memory CD45RA T cells (TEMRA). In vitro, we found the critical role of p90RSK activation in upregulating (1) CD38+/T-bet+ memory and naïve B, and myeloid cells, (2) senescence-associated β-gal staining, and (3) mitochondrial reactive oxygen species (ROS) after ionizing radiation (IR). These data suggest the crucial role of p90RSK activation in immunosenescence. The critical role of p90RSK activation in immune cells and T-bet induction in upregulating atherosclerosis formation has been reported. Furthermore, T-bet directly binds to the CD38 promoter region and upregulates CD38 expression. Since both T-bet and CD38 play a significant role in the process of immunosenescence, our data provide a cellular and molecular mechanism that links RT-induced p90RSK activation and the immunosenescence with T-bet and CD38 induction observed in thoracic cancer patients treated by RT and suggests that targeting the p90RSK/T-bet/CD38 pathway could play a role in preventing the radiation-associated CVD and improving cancer prognosis by inhibiting immunosenescence.

Treatment-related pulmonary adverse events induced by chemoradiation and Durvalumab affect survival in locally advanced non-small cell lung cancer

PURPOSE

We compared treatment-related pulmonary adverse events (TRPAE), progression-free survival (PFS), and overall survival (OS) among locally advanced non-small cell lung cancer (NSCLC) patients who received concurrent chemoradiotherapy (CRT) versus CRT followed by immune check point inhibitor (ICI) immunotherapy (CRTI).

MATERIALS AND METHODS

TRPAE was defined as any pulmonary events as defined in CTCAE v.5 occurring within 12 months after completion of radiotherapy. Outcomes were compared between CRT and CTRI by Cox proportional hazard regression and Kaplan-Meier analyses. We also assessed if TRPAE-induced discontinuation of ICI affected survival.

RESULTS

We analyzed 326 patients treated between July 2010 and November 2019; 195 patients received CRT and 131 received CRTI. The incidences of severe grade ≥ 3 TRPAE were similar between the two groups, however, symptomatic TRPAE was almost doubled in CRTI group (65.7 % CTRI vs 35.9 % CRT, P < 0.0001). The rates of 4-year OS and PFS were 54.5 % vs 36.7 % (P = 0.0003) and 43.8 % vs 35.8 % (P = 0.038) in CRT + Durvalumab and CRT group, respectively. Receipt of ICI Durvalumab was associated with better 4-year OS (HR 0.53, 95 % CI 0.36-0.78, P = 0.001) and PFS (HR 0.55, 95 % CI 0.38-0.80, P = 0.002). Patients who discontinued ICI because of TRPAE had worse 4-year OS (P = 0.001) and higher rates of distant metastasis (P = 0.003) than those who completed planned ICI after developing TRPAE.

CONCLUSION

CRT followed by adjuvant ICI led to improved 4-year OS and PFS consistent with published data. CRTI was associated with higher incidence of grade ≥ 2 TRPAE in both high and low mean lung dose groups without significant difference in grade ≥ 3 TRPAE. Discontinuation of ICI due to TRPAE was associated with poorer OS and distant disease control than completing ICI as planned after developing TRPAE.

Interleukin-6 blockade abrogates immunotherapy toxicity and promotes tumor immunity

Immune checkpoint blockade (ICB) therapy frequently induces immune-related adverse events. To elucidate the underlying immunobiology, we performed a deep immune analysis of intestinal, colitis, and tumor tissue from ICB-treated patients with parallel studies in preclinical models. Expression of interleukin-6 (IL-6), neutrophil, and chemotactic markers was higher in colitis than in normal intestinal tissue; T helper 17 (Th17) cells were more prevalent in immune-related enterocolitis (irEC) than T helper 1 (Th1). Anti-cytotoxic T-lymphocyte-associated antigen 4 (anti-CTLA-4) induced stronger Th17 memory in colitis than anti-program death 1 (anti-PD-1). In murine models, IL-6 blockade associated with improved tumor control and a higher density of CD4+/CD8+ effector T cells, with reduced Th17, macrophages, and myeloid cells. In an experimental autoimmune encephalomyelitis (EAE) model with tumors, combined IL-6 blockade and ICB enhanced tumor rejection while simultaneously mitigating EAE symptoms versus ICB alone. IL-6 blockade with ICB could de-couple autoimmunity from antitumor immunity.

Distinct Immunophenotypes of T Cells in Bronchoalveolar Lavage Fluid From Leukemia Patients With Immune Checkpoint Inhibitors-Related Pulmonary Complications

Patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) treated with immune checkpoint inhibitors (ICIs) are at risk of pneumonitis as well as pneumonia (combined henceforth as ICI-related pulmonary complications). Little is known about the cellular and molecular mechanisms underlying ICI-related pulmonary complications. We characterized lymphocytes from bronchoalveolar lavage (BAL) fluid and peripheral blood from seven AML/MDS patients with pulmonary symptoms after ICI-based therapy (ICI group) and four ICI-naïve AML/MDS patients with extracellular bacterial or fungal pneumonias (controls). BAL T cells in the ICI group were clonally expanded, and BAL IFNγ⁺ IL-17^- CD8⁺ T and CXCR3⁺ CCR6⁺ Th17/Th1 cells were enriched in the ICI group. Our data suggest that these cells may play a critical role in the pathophysiology of ICI-related pulmonary complications. Understanding of these cell populations may also provide predictive and diagnostic biomarkers of ICI-related pulmonary complications, eventually enabling differentiation of pneumonitis from pneumonia in AML/MDS patients receiving ICI-based therapies.

Recurrent pseudogout after therapy with immune checkpoint inhibitors: a case report with immunoprofiling of synovial fluid at each flare

Background

Despite ground-breaking clinical success in the treatment of different cancers, immune checkpoint inhibitors can cause profound inflammatory and immune-related adverse events. Autoimmune inflammatory arthritis following immune checkpoint inhibitor treatment has been reported; however, to date, no cases of crystal arthritis following immune checkpoint inhibitors have been identified.

Case presentation

We report the first case of recurrent pseudogout, an inflammatory crystal arthritis, in a patient treated with nivolumab, a PD-1 inhibitor, for renal cell carcinoma. The patient had recurrent pseudogout flares about week to 10 days after each nivolumab infusion. After treatment with prophylactic colchicine, the patient well tolerated additional nivolumab infusions without adverse events. In parallel, we characterized immune cells of synovial fluid at each flare. Immunoprofiling of synovial fluid showed that the proportion of inflammatory IL-17-producing CD4⁺ T cells and amount of IL-17 were notably increased in synovial fluid with every recurrent flair, and correlated with the increase in number of synovial neutrophils, suggesting a potential role of T helper 17 (Th17) cells in neutrophil-driven inflammation during pseudogout arthritis.

Conclusions

This case suggests a potential influence of Th17 cells on the neutrophil recruitment and neutrophil-driven inflammatory events leading to pseudogout induced by immune checkpoint inhibitor therapy.

Insights Into the Molecular Mechanisms of T Follicular Helper-Mediated Immunity and Pathology

T follicular helper (Tfh) cells play key role in providing help to B cells during germinal center (GC) reactions. Generation of protective antibodies against various infections is an important aspect of Tfh-mediated immune responses and the dysregulation of Tfh cell responses has been implicated in various autoimmune disorders, inflammation, and malignancy. Thus, their differentiation and maintenance must be closely regulated to ensure appropriate help to B cells. The generation and function of Tfh cells is regulated by multiple checkpoints including their early priming stage in T zones and throughout the effector stage of differentiation in GCs. Signaling pathways activated downstream of cytokine and costimulatory receptors as well as consequent activation of subset-specific transcriptional factors are essential steps for Tfh cell generation. Thus, understanding the mechanisms underlying Tfh cell-mediated immunity and pathology will bring into spotlight potential targets for novel therapies. In this review, we discuss the recent findings related to the molecular mechanisms of Tfh cell differentiation and their role in normal immune responses and antibody-mediated diseases.

IL22 Promotes Kras-Mutant Lung Cancer by Induction of a Protumor Immune Response and Protection of Stemness Properties

Somatic KRAS mutations are the most common oncogenic variants in lung cancer and are associated with poor prognosis. Using a Kras-induced lung cancer mouse model, CC-LR, we previously showed a role for inflammation in lung tumorigenesis through activation of the NF-κB pathway, along with induction of interleukin 6 (IL6) and an IL17-producing CD4+ T-helper cell response. IL22 is an effector molecule secreted by CD4+ and γδ T cells that we previously found to be expressed in CC-LR mice. IL22 mostly signals through the STAT3 pathway and is thought to act exclusively on nonhematopoietic cells with basal IL22 receptor (IL22R) expression on epithelial cells. Here, we found that higher expression of IL22R1 in patients with KRAS-mutant lung adenocarcinoma was an independent indicator of poor recurrence-free survival. We then showed that genetic ablation of Il22 in CC-LR mice (CC-LR/IL22KO mice) caused a significant reduction in tumor number and size. This was accompanied by significantly lower tumor cell proliferation, angiogenesis, and STAT3 activation. Il22 ablation was also associated with significant reduction in lung-infiltrating inflammatory cells and expression of protumor inflammatory cytokines. Conversely, this was accompanied with increased antitumor Th1 and cytotoxic CD8+ T-cell responses, while suppressing the protumor immunosuppressive T regulatory cell response. In CC-LR/IL22KO mice, we found significantly reduced expression of core stemness genes and the number of prototypical SPC+CCSP+ stem cells. Thus, we conclude that IL22 promotes Kras-mutant lung tumorigenesis by driving a protumor inflammatory microenvironment with proliferative, angiogenic, and stemness contextual cues in epithelial/tumor cells. Cancer Immunol Res; 6(7); 788-97. ©2018 AACR.

Generation of RORγt+ Antigen-Specific T Regulatory 17 Cells from Foxp3+ Precursors in Autoimmunity

Th17 cells are potent mediators in autoimmune diseases, and RORγt is required for their development. Recent studies have shown that RORγt⁺ Treg cells in the gut regulate intestinal inflammation by inhibiting effector T cell function. In the current study, we report that RORγt⁺ Treg cells were also found in lymph nodes following immunization. Not only distinct from intestinal RORγt⁺ Treg cells in their transcriptomes, peripheral RORγt⁺ Treg cells were derived from Foxp3⁺ thymic Treg cells in an antigen-specific manner. Development of these RORγt⁺ Treg cells, coined T regulatory 17 (Tr17) cells, depended on IL-6/Stat3 signaling. Tr17 cells showed suppressive activity against antigen-specific effector T cells in vitro. In addition, Tr17 cells efficiently inhibited myelin-specific Th17-cell-mediated CNS auto-inflammation in a passive EAE model. Collectively, our study demonstrates that Tr17 cells are effector Treg cells that potentially restrict autoimmunity.

In Vivo Assay for Detection of Antigen-specific T-cell Cytolytic Function Using a Vaccination Model

Current methodologies for antigen-specific killing are limited to in vitro use or utilized in infectious disease models. However, there is not a protocol specifically intended to measure antigen-specific killing without an infection. This protocol is designed and describes methods to overcome these limitations by allowing for the detection of antigen-specific killing of a target cell by CD8⁺ T cells in vivo. This is accomplished by merging a vaccination model with a traditional CFSE-labeled target killing assay. This combination allows the researcher to assess the antigen-specific CTL potential directly and quickly as the assay is not dependent upon tumor growth or infection. In addition, the readout is based on flow cytometry and so should be readily accessible to most researchers. The major limitation of the study is identifying the timeline in vivo that is appropriate to the hypothesis being tested. Variations in antigen strength and mutations in the T cells that may result in differential cytolytic function need to be carefully assessed to determine the optimal time for cell harvest and assessment. The appropriate concentration of peptide for vaccination has been optimized for hgp10025-33 and OVA257-264, but further validation would be needed for other peptides that may be more appropriate to a given study. Overall, this protocol allows a quick assessment of killing function in vivo and can be adapted to any given antigen.

STAT4 Regulates the CD8+ Regulatory T Cell/T Follicular Helper Cell Axis and Promotes Atherogenesis in Insulin-Resistant Ldlr-/- Mice

The metabolic syndrome and diabetic conditions support atherosclerosis, but the exact mechanisms for accelerated atherogenesis remain unclear. Although the proinflammatory role of STAT4 in atherosclerosis and diet-induced insulin resistance (IR) was recently established, the impact of STAT4 on atherogenesis in conditions of IR is not known. In this study, we generated Stat4^-/-Ldlr^-/- mice that were fed a diabetogenic diet with added cholesterol (DDC). DDC-fed Stat4^-/-Ldlr^-/- mice demonstrated improved glucose tolerance, insulin sensitivity, and a 36% reduction in atherosclerosis compared with Ldlr^-/- controls. Interestingly, we detected a reduction in T follicular helper (Tfh) cells and plasma B cells but a sharp elevation in CD8⁺ regulatory T cells (Tregs) in spleens and aortas of Stat4^-/-Ldlr^-/- mice compared with Ldlr^-/- mice. Similarly, STAT4 deficiency supported CD8⁺ Treg differentiation in vitro. STAT4-deficient CD8⁺ Tregs suppressed Tfh cell and germinal center B cell development upon immunization with keyhole limpet hemocyanin, indicating an important role for STAT4 in CD8⁺ Treg functions in vivo. Furthermore, adoptive transfer of Stat4^-/-Ldlr^-/- CD8⁺ Tregs versus Ldlr^-/- CD8⁺ Tregs resulted in a significant reduction in plaque burden and suppression of Tfh cell and germinal center B cells in DDC-fed Ldlr^-/- recipients. STAT4 expression in macrophages (MΦs) also affected the Tfh/CD8⁺ Treg axis, because conditioned media from Stat4^-/-Ldlr^-/- MΦs supported CD8⁺ Treg differentiation, but not Tfh cell differentiation, in a TGF-β-dependent manner. These findings suggest a novel mechanism by which STAT4 supports atherosclerosis in IR Ldlr^-/- mice via STAT4-dependent MΦs, as well as cell-intrinsic suppression of CD8⁺ Treg generation and functions and maintenance of Tfh cell generation and the accompanying humoral immune response.

Concomitant suppression of TH2 and TH17 cell responses in allergic asthma by targeting retinoic acid receptor-related orphan receptor γt

BACKGROUND

Allergic asthma is a heterogeneous chronic inflammatory disease of the airways with a massive infiltration of eosinophils or neutrophils mediated by allergen-specific T_H2 and T_H17 cells, respectively. Therefore successful treatment of allergic asthma will require suppression of both T_H2 and T_H17 cells.

OBJECTIVE

We sought to investigate the role of the T_H17 cell pathway in regulating T_H2 cell responses in allergic asthma.

METHODS

Allergic asthma was induced by intranasal challenge with proteinase allergens in C57BL/6, Il17a^-/-Il17f^-/-, and retinoic acid receptor-related orphan receptor γt (RORγt)^gfp/gfp mice. A pharmacologic RORγt inhibitor was used to evaluate its preventive and therapeutic effects in allergic asthma. Characteristics of allergic airway inflammation were analyzed by using flow cytometry, histology, quantitative real-time PCR, and ELISA. Mixed bone marrow chimeric mice, fate mapping analysis, short hairpin RNA transduction, and in vitro T-cell differentiation were used for mechanistic studies.

RESULTS

Mice deficient in IL-17A and IL-17F, as well as RORγt, exhibited a significant reduction not only in T_H17 cell responses but also in T_H2 cell responses in an animal model of allergic asthma. Similarly, mice treated with an RORγt inhibitor had significantly diminished T_H17 and T_H2 cell responses, leading to reduced neutrophil and eosinophil numbers in the airway. RORγt-deficient T cells were intrinsically defective in differentiating into T_H2 cells and expressed increased levels of B-cell lymphoma 6 (Bcl6). Bcl6 knockdown resulted in a remarkable restoration of T_H2 cell differentiation in RORγt-deficient T cells. Blockade of RORγt also significantly hampered the differentiation of human T_H2 and T_H17 cells from naive CD4⁺ T cells.

CONCLUSION

RORγt in T cells is required for optimal T_H2 cell differentiation by suppressing Bcl6 expression; this finding suggests that targeting RORγt might be a promising approach for the treatment of allergic asthma by concomitantly suppressing T_H17 and T_H2 cell responses in the airway.

IL-21 Receptor Signaling Is Essential for Optimal CD4+ T Cell Function and Control of Mycobacterium tuberculosis Infection in Mice

In this study, we determined the role of IL-21R signaling in Mycobacterium tuberculosis infection, using IL-21R knockout (KO) mice. A total of 50% of M. tuberculosis H37Rv-infected IL-21R KO mice died in 6 mo compared with no deaths in infected wild type (WT) mice. M. tuberculosis-infected IL-21R KO mice had enhanced bacterial burden and reduced infiltration of Ag-specific T cells in lungs compared with M. tuberculosis-infected WT mice. Ag-specific T cells from the lungs of M. tuberculosis-infected IL-21R KO mice had increased expression of T cell inhibitory receptors, reduced expression of chemokine receptors, proliferated less, and produced less IFN- γ, compared with Ag-specific T cells from the lungs of M. tuberculosis-infected WT mice. T cells from M. tuberculosis-infected IL-21R KO mice were unable to induce optimal macrophage responses to M. tuberculosis. This may be due to a decrease in the Ag-specific T cell population. We also found that IL-21R signaling is associated with reduced expression of a transcriptional factor Eomesodermin and enhanced functional capacity of Ag-specific T cells of M. tuberculosis-infected mice. The sum of our findings suggests that IL-21R signaling is essential for the optimal control of M. tuberculosis infection.

Multifaceted Role of BTLA in the Control of CD8+ T-cell Fate after Antigen Encounter

Purpose: Adoptive T-cell therapy using autologous tumor-infiltrating lymphocytes (TIL) has shown an overall clinical response rate 40%-50% in metastatic melanoma patients. BTLA (B-and-T lymphocyte associated) expression on transferred CD8⁺ TILs was associated with better clinical outcome. The suppressive function of the ITIM and ITSM motifs of BTLA is well described. Here, we sought to determine the functional characteristics of the CD8⁺BTLA⁺TIL subset and define the contribution of the Grb2 motif of BTLA in T-cell costimulation.Experimental Design: We determined the functional role and downstream signal of BTLA in both human CD8⁺ TILs and mouse CD8⁺ T cells. Functional assays were used including single-cell analysis, reverse-phase protein array (RPPA), antigen-specific vaccination models with adoptively transferred TCR-transgenic T cells as well as patient-derived xenograft (PDX) model using immunodeficient NOD-scid IL2Rgammanull (NSG) tumor-bearing mice treated with autologous TILs.Results: CD8⁺BTLA^- TILs could not control tumor growth in vivo as well as their BTLA⁺ counterpart and antigen-specific CD8⁺BTLA^- T cells had impaired recall response to a vaccine. However, CD8⁺BTLA⁺ TILs displayed improved survival following the killing of a tumor target and heightened "serial killing" capacity. Using mutants of BTLA signaling motifs, we uncovered a costimulatory function mediated by Grb2 through enhancing the secretion of IL-2 and the activation of Src after TCR stimulation.Conclusions: Our data portrays BTLA as a molecule with the singular ability to provide both costimulatory and coinhibitory signals to activated CD8⁺ T cells, resulting in extended survival, improved tumor control, and the development of a functional recall response. Clin Cancer Res; 23(20); 6151-64. ©2017 AACR.

IL-21-dependent expansion of memory-like NK cells enhances protective immune responses against Mycobacterium tuberculosis

Natural killer (NK) cells are traditionally considered as innate cells, but recent studies suggest that NK cells can distinguish antigens, and that memory NK cells expand and protect against viral pathogens. Limited information is available about the mechanisms involved in memory-like NK cell expansion, and their role in bacterial infections and vaccine-induced protective immune responses. In the current study, using a mouse model of tuberculosis (TB) infection, we found that interferon-gamma producing CD3-NKp46+CD27+KLRG1+ memory-like NK cells develop during Bacille Calmette-Guérin vaccination, expand, and provide protection against challenge with Mycobacterium tuberculosis (M. tb). Using antibodies, short interfering RNA and gene-deleted mice, we found that expansion of memory-like NK cells depends on interleukin 21 (IL-21). NKp46+CD27+KLRG1+ NK cells expanded in healthy individuals with latent TB infection in an IL-21-dependent manner. Our study provides first evidence that memory-like NK cells survive long term, expansion depends on IL-21, and involved in vaccine-induced protective immunity against a bacterial pathogen.

Modified low density lipoprotein (mLDL) uptake by B cells alters B cell phenotype and impacts atherosclerosis

Atherosclerosis is a multifaceted chronic inflammatory disease characterized by the accumulation of modified lipoproteins and immune cells in the aortic wall and vascular dysfunction. The uptake of modified low density lipoproteins (mLDL) by MFs plays an important role in atherosclerosis through the modulation of cholesterol metabolism and MF activation. To date, the impact of mLDL on B cell phenotype and functions is unaddressed. We show that B cells can uptake acetylated and oxidized LDL (acLDL and oxLDL, respectively) via a dynamin-dependent pathway in a concentration, time, and temperature-dependent manner. Assessment of the transcriptional profiles of in vivo acLDL+ B cells and acLDL- B cells by RNAseq suggests that acLDL+ B cells assume an anergic like phenotype. Anergy plays an important role in keeping autoreactive B cells in a state of unresponsiveness and the loss of anergy contributes to the development of autoimmune diseases. Currently, nothing is known about the role and regulation of B cell anergy in atherosclerosis. We show here for the first time that GRAIL, an E3 ubiquitin ligase associated with T cell tolerance, is expressed in B cells. To determine whether B cell-specific GRAIL expression plays a role in atherosclerosis, we performed adoptive transfer of GRAIL-deficient or GRAIL-sufficient B cells into B-cell-deficient mice on apolipoprotein-E deficient background (uM−/− Apoe−/−) mice and examined atherogenesis after 8 weeks of western diet feeding. B cell-specific GRAIL-deficiency supported plaque burden and orchestrated inflammation in the aortic wall. These data suggest that there is a specific mechanism by which B cells recognize mLDL and regulate their anergy-dependent response to mLDL in atherosclerosis.

STAT4 regulates CD8+Treg/Tfh cell axis and promotes atherogenesis in insulin-resistant Ldlr−/− mice

The metabolic syndrome support atherosclerosis, but the exact mechanisms for accelerated atherogenesis remain unclear. While the pro-inflammatory role of signal transducer and activator of transcription 4 (STAT4) in atherosclerosis and diet-induced insulin resistance (IR) was recently established, an impact of STAT4 on atherogenesis in conditions of IR is not known. To study the role of STAT4 in IR-accelerated atherosclerosis we generated Stat4−/−Ldlr−/− mice that were fed a diabetogenic diet with added cholesterol (DDC). DDC fed Stat4−/− Ldlr−/−mice demonstrated improved glucose tolerance, insulin sensitivity, and a 36% reduction in atherosclerosis compared with Ldlr−/−controls. Interestingly, we detected a reduction in T follicular helper (Tfh) and plasma B cells, but a sharp elevation in CD8+ Tregs in spleens and aortas of Stat4−/−Ldlr−/−versus Ldlr−/−mice. Similarly, STAT4 deficiency supported CD8+ Treg differentiation in vitro. Additionally, Stat4-deficient CD8+Tregs suppressed Tfh and germinal center B cell development upon immunization with KLH indicating an important role for STAT4 in CD8+ Treg functions in vivo. Effects of STAT4 deficiency were not only restricted to T cells, but had a significant impact on macrophage phenotype. Stat4−/−Ldlr−/− macrophages displayed decreased IFNγ and MHC-II expression. Conditioned media from Stat4−/−Ldlr−/−MFs supported CD8+ Treg but not Tfh cell differentiation in TGFβ-dependent manner, suggesting a role for MF-specific STAT4 in Th cell differentiation. These new findings suggest a novel mechanism by which STAT4 supports atherosclerosis in obese, IR Ldlr−/− mice via increases in MF activation, and modulation of the Tfh/ CD8+ Treg axis systemically and within the aorta.

Insights into the development and regulation of T follicular helper cells

T follicular helper (Tfh) cells are specialized subset of T helper (Th) cells necessary for germinal center reaction, affinity maturation and the differentiation of germinal center B cells to antibody-producing plasma B cells and memory B cells. The differentiation of Tfh cells is a multistage, multifactorial process involving a variety of cytokines, surface molecules and transcription factors. While Tfh cells are critical components of protective immune responses against pathogens, regulation of these cells is crucial to prevent autoimmunity and airway inflammation. Recently, it has been noted that Tfh cells could be potentially implicated either in cancer progression or prevention. Thus, the elucidation of the mechanisms that regulate Tfh cell differentiation, function and fate should highlight potential targets for novel therapeutic approaches. In this review, we summarize the latest advances in our understanding of the regulation of Tfh cell differentiation and their role in health and disease.

T helper 2 and T follicular helper cells: Regulation and function of interleukin-4

Type 2 immunity is characterized by expression of the cytokines interleukin (IL)-4, IL-5, IL-9 and IL-13, which can function in mediating protective immunity in the host or possess a pathogenic role. T helper (Th) 2 cells have emerged to play a beneficial role in mediating anti-parasitic immunity and are also known to be key players in mediating allergic diseases. In addition to the Th2 cells, recent studies have identified T follicular helper (Tfh) cells as an alternative source of IL-4 to regulate type 2 humoral immune responses, indicating that Th2 and Tfh cells exhibit overlapping phenotypical and functional characteristics. Th2 and Tfh cells appear to utilize distinct mechanisms for regulation of IL-4 expression; however unlike Th2 cells, the regulation and function of Tfh-derived IL-4 is not yet fully understood. Understanding of the molecular mechanisms for IL-4 expression and function in both cell subsets will be beneficial for the development of future therapeutic interventions.

Targeting the Src Homology 2 (SH2) Domain of Signal Transducer and Activator of Transcription 6 (STAT6) with Cell-Permeable, Phosphatase-Stable Phosphopeptide Mimics Potently Inhibits Tyr641 Phosphorylation and Transcriptional Activity

Signal transducer and activator of transcription 6 (STAT6) transmits signals from cytokines IL-4 and IL-13 and is activated in allergic airway disease. We are developing phosphopeptide mimetics targeting the SH2 domain of STAT6 to block recruitment to phosphotyrosine residues on IL-4 or IL-13 receptors and subsequent Tyr641 phosphorylation to inhibit the expression of genes contributing to asthma. Structure-affinity relationship studies showed that phosphopeptides based on Tyr631 from IL-4Rα bind with weak affinity to STAT6, whereas replacing the pY+3 residue with simple aryl and alkyl amides resulted in affinities in the mid to low nM range. A set of phosphatase-stable, cell-permeable prodrug analogues inhibited cytokine-stimulated STAT6 phosphorylation in both Beas-2B human airway cells and primary mouse T-lymphocytes at concentrations as low as 100 nM. IL-13-stimulated expression of CCL26 (eotaxin-3) was inhibited in a dose-dependent manner, demonstrating that targeting the SH2 domain blocks both phosphorylation and transcriptional activity of STAT6.

Batf is important for IL-4 expression in T follicular helper cells

Apart from T helper (Th)-2 cells, T follicular helper (Tfh) cells are a major class of IL-4-producing T cells, required for regulation of type 2 humoral immunity; however, transcriptional control of IL-4 production in Tfh cells remains mainly unknown. Here, we show that the basic leucine zipper transcription factor ATF-like, Batf is important for IL-4 expression in Tfh cells rather than in canonical Th2 cells. Functionally, Batf in cooperation with interferon regulatory factor (IRF) 4 along with Stat3 and Stat6 trigger IL-4 production in Tfh cells by directly binding to and activation of the CNS2 region in the IL-4 locus. In addition, Batf-to-c-Maf signalling is an important determinant of IL-4 expression in Tfh cells. Batf deficiency impairs the generation of IL-4-producing Tfh cells that results in protection against allergic asthma. Our results thus indicate a positive role of Batf in promoting the generation of pro-allergic IL-4-producing Tfh cells.

Transcriptional regulation of IL-4 expression in T follicular helper cells (IRM15P.456)

Apart from Th2 cells T follicular helper (Tfh) cells are a major class of IL-4 producing T cells, required for regulation of type 2 humoral immune responses. Although the transcriptional control of IL-4 in Th2 cells has been extensively investigated, the precise regulation mechanism(s) of IL-4 production in Tfh cells remains mainly unknown. In the current study, we found that the transcription factor Batf, a member of the AP-1/Jun family is essential for IL-4 expression in Tfh cells. Remarkably, Batf deficiency leads to decreased IL-4 production selectively in Tfh cells but not in conventional Th2 cells and subsequently to reduction in their pro-allergic pathogenicity. Batf in cooperation with Interferon regulatory factor (IRF)4 controls IL-4 production in Tfh cells by directly binding to and activation of the CNS2 region of the IL-4 locus. The transcription factors Stat3 and Stat6 also aid in Batf/IRF4 binding to the CNS2 locus thus playing a crucial role in Batf-mediated regulation of IL-4 in Tfh cells. We also found that enhanced expression of Batf in Tfh cells is largely dependent on IL-4/Stat6 signaling, indicating towards a positive feedback loop in controlling Batf-IL-4 expression in Tfh cells. Our results thus identify a novel and critical role of Batf in promoting the generation of pro-allergic IL-4 producing Tfh cells.

Grail controls Th2 cell development by targeting STAT6 for degradation

T helper (Th)-2 cells are the major players in allergic asthma; however, the mechanisms that control Th2-mediated inflammation are poorly understood. Here we find that enhanced expression of Grail, an E3 ubiquitin ligase, in Th2 cells depends on IL-4-signaling components, Stat6 and Gata3 that bind to and transactivate the Grail promoter. Grail-deficiency in T cells leads to increased expression of Th2 effector cytokines in vitro and in vivo and Grail deficient mice are more susceptible to allergic asthma. Mechanistically, the enhanced effector function of Grail-deficient Th2 cells is mediated by increased expression of Stat6 and IL-4 receptor α-chain. Grail interacts with Stat6 and targets it for ubiquitination and degradation. Thus, our results indicate that Grail plays a critical role in controlling Th2 development through a negative feedback loop.

Generation of a new therapeutic peptide that depletes myeloid-derived suppressor cells in tumor-bearing mice

Cancer immune evasion is an emerging hallmark of disease progression. Functional studies to understand the role of myeloid-derived suppressor cells (MDSC) in the tumor microenvironment however, are limited by the lack of available specific cell surface markers. We adapted a competitive peptide phage display platform to identify candidate peptides binding MDSC specifically and generated peptide-Fc fusion proteins (peptibody). In multiple tumor models peptibody injection iv completely depleted blood, splenic, and intratumoral MDSC in tumor-bearing mice, without affecting proinflammatory immune cell types, such as dendritic cells. While control Gr-1 antibody depleted primarily granulocytic MDSC, peptibodies depleted both granulocytic and monocytic subsets. Remarkably, peptibody treatment was associated with inhibition of tumor growth in vivo, which was superior to Gr-1. Immunoprecipitation of MDSC membrane proteins identified S100 family proteins as candidate targets. Our strategy may be useful to identify novel diagnostic and therapeutic surface targets on rare cell subtypes, including human MDSC.

Gene related to anergy in lymphocytes deficiency confers spontaneous tumor regression (TUM2P.897)

T cell tolerance is the main obstacle to successful cancer immunotherapy; thus, today it is a high priority to develop strategies to break T cell tolerance and thereafter enhance T-cell cytotoxicity towards tumor cells. We, as well as other groups, have acknowledged the E3 ubiquitin ligase, Gene related to anergy in lymphocytes (Grail), as an essential component of T-cell tolerance phenotype. Here we report that Grail expression is highly upregulated in CD8+ T cells infiltrated into the EG-7 tumors compared to T cells in lymphoid tissues, and Grail deficiency confers spontaneous protection against inoculated EG-7 tumors. Importantly, therapeutic transfer of naïve tumor-antigen-specific Grail deficient CD8+ T cells into the wild-type hosts was sufficient to reject established tumors. Mechanistically, Grail deficient CD8+ T cells exhibit augmented effector cytokine expression and enhanced cytolytic function compared to wild-type CD8+ T cells, and are resistant to the suppression mediated by regulatory T cells. Moreover, the elevated cytotoxic function of Grail-deficient CD8+ T cells essentially depends on TCR and IL-21-signaling pathway; Grail promotes IL21R ubiquitination and degradation. Altogether, our data demonstrate that Grail is a crucial factor that controls anti-tumor activity of cytotoxic T cells, thus, inhibition of Grail may be a beneficial immunotherapeutic approach to induce potent immune responses against established tumors.

T-cell tolerance in cancer

T cells are the master regulators of adaptive immune responses and maintenance of their tolerance is critical to prevent autoimmunity. However, in the case of carcinogenesis, the tumor microenvironment aids T-cell tolerance, which contributes to uncontrolled tumor growth. Recently, there has been significant progress in understanding the intrinsic extracellular (positive and negative costimulatory molecules on APCs) and intracellular mechanisms (E3 ubiquitin ligases, transcriptional and epigenetic repressors), as well as extrinsic mechanisms (Tregs and tolerogenic dendritic cells) that are required for the implementation and maintenance of T-cell tolerance. Ultimately, understanding and manipulating T-cell tolerance will help to break the tolerance state in cancer.

Essential role of E3 ubiquitin ligase activity of GRAIL in T cell functions (P1111)

T cells are the master regulators of adaptive immune responses, and many autoimmune diseases arise due to a breakdown of self-tolerance in T cells. Understanding of the molecular mechanisms underlying T cell tolerance will lead to development of pharmacological approaches either to promote the tolerance state in terms of autoimmunity or to break tolerance in cancer. E3 ubiquitin ligases have been placed among the essential molecules involved in the regulation of T cell functions and T cell tolerance. We as well as other groups have reported that T cells activated in the absence of both CD28 and ICOS costimulation developed into tolerant T cells, associated with markedly upregulated expression of the E3 ubiquitin ligase GRAIL. In order to understand the physiological function of GRAIL, we generated mice deficient in Grail by replacing region that encompassing most of the RING domain and responsible for E3 ubiquitin activity. Remarkably, genetic inactivation of E3 ubiquitin ligase function of GRAIL led to T cell hyper-responsiveness to TCR/CD3z signaling and their independency to costimulation for activation. As a result, GRAIL-deficient mice were more predisposing to autoimmune diseases. On the other hand, modulation of GRAIL function helped to boost T cell immune responses to cancer, and, therefore, mediate tumor rejection. Thus, modulation of the E3 ligase activity of GRAIL might be an important approach to control T cell functions in autoimmunity or cancer.

A genomic regulatory element that directs assembly and function of immune-specific AP-1-IRF complexes (P1322)

Interferon regulatory factor 4 (IRF4) and IRF8 regulate B, T, macrophage, and dendritic cell differentiation. They are recruited to cis-regulatory Ets-IRF composite elements by PU.1 or Spi-B. How these IRFs target genes in most T cells is enigmatic given the absence of specific Ets partners. Chromatin immunoprecipitation sequencing in T helper 17 (T(H)17) cells reveals that IRF4 targets sequences enriched for activating protein 1 (AP-1)-IRF composite elements (AICEs) that are co-bound by BATF, an AP-1 factor required for T(H)17, B, and dendritic cell differentiation. IRF4 and BATF bind cooperatively to structurally divergent AICEs to promote gene activation and T(H)17 differentiation. The AICE motif directs assembly of IRF4 or IRF8 with BATF heterodimers and is also used in T(H)2, B, and dendritic cells. This genomic regulatory element and cognate factors appear to have evolved to integrate diverse immunomodulatory signals.

A genomic regulatory element that directs assembly and function of immune-specific AP-1-IRF complexes

Interferon regulatory factor 4 (IRF4) and IRF8 regulate B, T, macrophage, and dendritic cell differentiation. They are recruited to cis-regulatory Ets-IRF composite elements by PU.1 or Spi-B. How these IRFs target genes in most T cells is enigmatic given the absence of specific Ets partners. Chromatin immunoprecipitation sequencing in T helper 17 (T(H)17) cells reveals that IRF4 targets sequences enriched for activating protein 1 (AP-1)-IRF composite elements (AICEs) that are co-bound by BATF, an AP-1 factor required for T(H)17, B, and dendritic cell differentiation. IRF4 and BATF bind cooperatively to structurally divergent AICEs to promote gene activation and T(H)17 differentiation. The AICE motif directs assembly of IRF4 or IRF8 with BATF heterodimers and is also used in T(H)2, B, and dendritic cells. This genomic regulatory element and cognate factors appear to have evolved to integrate diverse immunomodulatory signals.

Reduced graft-versus-host disease in C3-deficient mice is associated with decreased donor Th1/Th17 differentiation

Graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation is mediated by the activation of recipient dendritic cells and subsequent proliferation of donor T cells. The complement system was recently shown to modulate adaptive immunity through an interaction of the complement system and lymphocytes. Complement proteins participate in the activation of dendritic cells, antigen presentation to T cells, and proliferation of T cells. Our studies with a murine model of bone marrow transplantation demonstrate that complement system regulates alloimmune responses in GVHD. Mice deficient in the central component of the complement system (C3(-/-)) had significantly lower GVHD-related mortality and morbidity compared with wild-type recipient mice. The numbers of donor-derived T cells, including IFN-γ(+), IL-17(+), and IL-17(+)IFN-γ(+) subsets, were decreased in secondary lymphoid organs of C3(-/-) recipients. Furthermore, the number of recipient CD8α(+)CD11c(+) cells in lymphoid organs was reduced. We conclude that C3 regulates Th1/17 differentiation in bone marrow transplantation, and define a novel function of the complement system in GVHD.

Transcription factor IRF4 determines germinal center formation through follicular T-helper cell differentiation

Follicular T-helper (T(FH)) cells cooperate with GL7(+)CD95(+) germinal center (GC) B cells to induce antibody maturation. Herein, we identify the transcription factor IRF4 as a T-cell intrinsic precondition for T(FH) cell differentiation and GC formation. After immunization with protein or infection with the protozoon Leishmania major, draining lymph nodes (LNs) of IFN-regulatory factor-4 (Irf4(-/-)) mice lacked GCs and GC B cells despite developing normal initial hyperplasia. GCs were also absent in Peyer's patches of naive Irf4(-/-) mice. Accordingly, CD4(+) T cells within the LNs and Peyer's patches failed to express the T(FH) key transcription factor B-cell lymphoma-6 and other T(FH)-related molecules. During chronic leishmaniasis, the draining Irf4(-/-) LNs disappeared because of massive cell death. Adoptive transfer of WT CD4(+) T cells or few L. major primed WT T(FH) cells reconstituted GC formation, GC B-cell differentiation, and LN cell survival. In support of a T-cell intrinsic IRF4 activity, Irf4(-/-) T(FH) cell differentiation was not rescued by close neighborhood to transferred WT T(FH) cells. Together with its known B lineage-specific roles during plasma cell maturation and class switch, our study places IRF4 in the center of antibody production toward T-cell-dependent antigens.

DUSP11 is required for innate immunity (167.4)

Dual specificity phosphatases (DUSPs) have been shown to play a critical role in regulation of various cellular processes. DUSP11 was previously demonstrated to bind to RNA-RNP complexes and RNA splicing factors and is a p53 target gene. Our in vitro studies showed that DUSP11 expression is induced in dendritic cells (DCs) upon stimulation by TLR ligands and in T cells upon CD3/CD28 activation suggesting the prominence of DUSP11 in immune responses. To examine the function of DUSP11 in regulating immune responses, we generated and analyzed DUSP11 deficient mice. We found that DUSP11 deficient antigen presenting cells produce decreased levels of proinflammatory cytokines during innate immune responses and CD4 T cells showed increased proliferation after activation but no apparent defect in in vitro T cell differentiation. However, our in vivo experiments demonstrated that DUSP11 deficient mice are defective in antigen-specific T cell responses and that they are more susceptible to Listeria monocytogenes infection. Using DC and T cell co-culture experiments we established that the DUSP11 signalling in DCs eventually regulates CD4 T cell activation. Together, these results demonstrate the critical role of DUSP11 in innate immunity.

STAT5 controls Tfh development (121.19)

Recent work has identified a new subset of CD4+ T cells named as T follicular helper (Tfh) cells that are localized in germinal centers and critical in germinal-center formation. Tfh cell differentiation is regulated by IL-6 and IL-21, possibly via STAT3 factor, and Bcl6 is specifically expressed in Tfh cells and required for their lineage specification. In current study, we characterized the role of STAT5 in developmental regulation of Tfh cells. We found that a constitutively active form of STAT5 effectively inhibited Tfh differentiation by suppressing the expression of Tfh-associated factors CXCR5, c-Maf, Bcl6, Batf and IL-21, whereas STAT5 deficiency greatly enhanced Tfh differentiation. In addition, deletion of STAT5 in CD4+ T cells in vivo resulted in enhanced development of Tfh cells and germinal center B cells, and led to an impairment of B cell tolerance, suggesting that STAT5 signaling controls the humoral immunity. This knowledge may help us to find ways to treat antibody-mediated autoimmune diseases.

Regulation of naïve T cell tolerance and regulatory T cell function by GRAIL (113.21)

CD4+ T cells are the master regulators of adaptive immune responses, and many autoimmune diseases arise due to a breakdown of self tolerance in CD4+ cells. Gene related to anergy in lymphocytes (GRAIL), the E3 ubiqutine ligase, has acknowledged as one of key molecules implicated in T cell activation and tolerance. In order to understand the physiological function of GRAIL in immune regulation, we have generated and analyzed GRAIL deficient mice. Naive T cells lacking GRAIL showed greatly enhanced proliferation and cytokine production after T cell receptor (TcR) activation. In addition, lack of GRAIL abrogated suppressive function of regulatory T (Treg) cells. We found that GRAIL deficient naive and Treg cells after TcR activation expressed substantially higher amounts of NFATc1 compared to wild-type cells, whereas the activation of other factors in AP-1 and NFκB pathways were normal. Our data also suggested that sustained TcR cell-surface expression in the absence of GRAIL led to selective NFATc1 expression in both naive T cells and Treg cells. In contrast to naïve T cells, GRAIL, through controlling NFATc1 expression, inhibits IL-21 production and upregulation of Th17-specific genes in Treg cells. Thus, the immune regulation by GRAIL in both naive and Treg cells is absolutely critical as evidenced by the failure of T cell tolerance induction and greatly increased susceptibility to autoimmune diseases of GRAIL deficient mice.

Dec2 regulates initial TH2 lineage commitment (99.12)

How naive CD4+ T cells commit to the T helper type 2 (TH2) lineage is poorly understood. Here we show that the basic helix-loop-helix transcription factor Dec2 is selectively expressed in TH2 cells. CD4+ T cells from Dec2-deficient mice exhibits defective TH2 differentiation in vitro and in vivo in an asthma model and in response to challenge with a parasite antigen. During early TH2 differentiation, Dec2 directly binds to and activates transcription of the Junb and Gata3 genes and promotes interleukin 4 expression. In addition, over-expression of GATA3 or JunB rescues TH2 cytokine expression in Dec2-deficient CD4+ T cells while optimal expression of these cytokines requires Dec2. As GATA3 induces Dec2 expression, these findings also indicate a feed-forward regulatory circuit during TH2 differentiation.

A critical role of GRAIL in T cell activation and tolerance (50.18)

T lymphocyte activation is tightly regulated to ensure effective elimination of invading pathogens as well as maintaining tolerance against self-tissues. Gene related to anergy in lymphocytes (GRAIL) is a type I transmembrane protein localized to endosomal compartment with homology to RING finger proteins whose expression was previously associated with induction of T cell tolerance in vitro. In order to understand the physiological function of GRAIL in immune regulation, we have generated and analyzed a Grail-deficient mouse model. We found that naïve T cells lacking GRAIL exhibited greatly enhanced proliferation and cytokine production after TcR activation and did not depend on CD28 and ICOS for their effector cytokine expression. We also determined that lack of GRAIL abrogated suppressive function of regulatory T cells. Both naïve and regulatory T cells from Grail-deficient mice were less efficient in down-regulation of their TcR/CD3 expression. In vivo, Grail-deficient mice were resistant to immune tolerance induction and when compared to the wild-type mice, exhibited greater susceptibility to autoimmune diseases. Our results thus indicate GRAIL as an essential regulator of T cell tolerance by regulating naïve T cell tolerance and regulatory T cell function.

Requirement for the basic helix-loop-helix transcription factor Dec2 in initial TH2 lineage commitment

How naive CD4(+) T cells commit to the T helper type 2 (T(H)2) lineage is poorly understood. Here we show that the basic helix-loop-helix transcription factor Dec2 was selectively expressed in T(H)2 cells. CD4(+) T cells from Dec2-deficient mice showed defective T(H)2 differentiation in vitro and in vivo in an asthma model and in response to challenge with a parasite antigen. Dec2 promoted expression of interleukin 4 (IL-4), IL-5 and IL-13 during early T(H)2 differentiation and directly bound to and activated transcription of genes encoding the transcription factors JunB and GATA-3. As GATA-3 induces Dec2 expression, our findings also indicate a feed-forward regulatory circuit during T(H)2 differentiation.

Critical regulation of early Th17 cell differentiation by interleukin-1 signaling

T helper (Th) 17 cells have been recently discovered in both mouse and human. Here we show that interleukin-1 (IL-1) signaling on T cells is critically required for the early programming of Th17 cell lineage and Th17 cell-mediated autoimmunity. IL-1 receptor1 expression in T cells, which was induced by IL-6, was necessary for the induction of experimental autoimmune encephalomyelitis and for early Th17 cell differentiation in vivo. Moreover, IL-1 signaling in T cells was required in dendritic cell-mediated Th17 cell differentiation from naive or regulatory precursors and IL-1 synergized with IL-6 and IL-23 to regulate Th17 cell differentiation and maintain cytokine expression in effector Th17 cells. Importantly, IL-1 regulated the expression of the transcription factors IRF4 and RORgammat during Th17 cell differentiation; overexpression of these two factors resulted in IL-1-independent Th17 cell polarization. Our data thus indicate a critical role of IL-1 in Th17 cell differentiation and this pathway may serve as a unique target for Th17 cell-mediated immunopathology.

Critical regulation of early Th17 cell differentiation by IL-1 signaling (48.24)

Th17 cells have been recently discovered in both mouse and human. Although IL-1 has been shown to be important in human Th17 cell differentiation with little knowledge of the underlying mechanism, its function in mouse is less clear. Here we show that IL-1R1 expression in T cells, which was induced by IL-6, was necessary for Th17-mediated autoimmunity and for early Th17 differentiation in vivo. Moreover, IL-1 signaling in T cells was required in dendritic cell-mediated Th17 differentiation from naïve or regulatory precursors and IL-1 synergized with IL-6 and IL-23 to regulate Th17 differentiation and maintain cytokine expression in effector Th17 cells. Importantly, IL-1 regulated the expression of IRF4 and RORγt during Th17 differentiation; over-expression of these two factors resulted in IL-1-independent Th17 polarization. Our data thus indicate a critical role of IL-1 in Th17 differentiation and this pathway may serve as a novel target for Th17-mediated immunopathology.

The work is supported by research grants from NIH (to CD), an Intramural Research Program of the NIEHS, NIH (to AMJ), Leukemia and Lymphoma Society (to CD) and MD Anderson Cancer Center (to CD and SSW) and the Gillson Longenbaugh Foundation (to SSW). RN is a recipient of a Scientist Development Grant from the American Heart Association. CD is a Trust Fellow of the MD Anderson Cancer Center, a Cancer Research Institute Investigator, a Leukemia and Lymphoma Society Scholar and an American Lung Association Career Investigator.

Developmental requirements of T follicular helper cells (90.10)

After activation, CD4+ helper T (Th) cells differentiate into distinct effector lineages. Th cell subset called T follicular helper (TFH) cells are recently found to be present in germinal centers and are characterized by their expression of chemokine (C-X-C motif) receptor 5 (CXCR5). Despite their potential importance in humoral immunity, the developmental regulation of TFH cells and their relationship with other Th subsets is unclear. We found that mouse TFH cells have a divergent gene expression profile from Th1, Th2 cells, and in vivo developed independently of these cell lineages. TFH cell generation was regulated by ICOS liagand expressed on B cells and was dependent on interleukin (IL)-21, IL-6 and signal transducer and activator of transcription 3 (STAT3). Although TFH cells shared IL-21 expression with Th17 cells, they did not express IL-17, IL-17F, IL-22. Moreover, differentiation of TFH cells did not require TGFβ or Th17-specific orphan nuclear receptors RORα?and RORγ in vivo. Most importantly, T cells activated in vitro in the presence of IL-21 but without TGFβ signaling preferentially acquired TFH gene expression and functioned to promote humoral immunity in vivo. Our data indicate that TFH cells are distinct in their gene expression, developmental regulation and immune function from Th1, Th2 or Th17 lineages.

The work is supported by a Scientist Development Grant from the American Heart Association.

A critical role of BTLA in peripheral T cell tolerance induction (48.18)

T cell activation and tolerance are delicately regulated by costimulatory molecules. Although B and T lymphocyte attenuator (BTLA) has been shown as a negative regulator for T cells activation, its role in peripheral T cell tolerance induction in vivo has not been addressed. In this study, we generated a novel strain of BTLA-deficient mice, and employed three different models to characterize the function of BTLA in controlling T cell tolerance. In an oral tolerance model, BTLA-deficient mice were found resistant to the induction of T cell tolerance to an oral antigen. Moreover, compared with wild-type OT-II cells, BTLA-/- OT-II cells were less susceptible to tolerance induction by high-dose Ova peptide administered intravenously. Finally, BTLA-/- OT-I cells caused autoimmune diabetes in RIP-mOVA recipient mice. Our results thus demonstrate an important role of BTLA in the induction of peripheral tolerance of both CD4+ and CD8+ T cells in vivo.

LFA-1 affinity regulation is necessary for the activation and proliferation of naive T cells

The activation of LFA-1 (lymphocyte function-associated antigen) is a critical event for T cell co-stimulation. The mechanism of LFA-1 activation involves both affinity and avidity regulation, but the role of each in T cell activation remains unclear. We have identified antibodies that recognize and block different affinity states of the mouse LFA-1 I-domain. Monoclonal antibody 2D7 preferentially binds to the low affinity conformation, and this specific binding is abolished when LFA-1 is locked in the high affinity conformation. In contrast, M17/4 can bind both the locked high and low affinity forms of LFA-1. Although both 2D7 and M17/4 are blocking antibodies, 2D7 is significantly less potent than M17/4 in blocking LFA-1-mediated adhesion; thus, blocking high affinity LFA-1 is critical for preventing LFA-1-mediated adhesion. Using these reagents, we investigated whether LFA-1 affinity regulation affects T cell activation. We found that blocking high affinity LFA-1 prevents interleukin-2 production and T cell proliferation, demonstrated by TCR cross-linking and antigen-specific stimulation. Furthermore, there is a differential requirement of high affinity LFA-1 in the activation of CD4(+) and CD8(+) T cells. Although CD4(+) T cell activation depends on both high and low affinity LFA-1, only high affinity LFA-1 provides co-stimulation for CD8(+) T cell activation. Together, our data demonstrated that the I-domain of LFA-1 changes to the high affinity state in primary T cells, and high affinity LFA-1 is critical for facilitating T cell activation. This implicates LFA-1 activation as a novel regulatory mechanism for the modulation of T cell activation and proliferation.

Cutting edge: in vitro generated Th17 cells maintain their cytokine expression program in normal but not lymphopenic hosts

Upon activation, naive CD4(+) T cells differentiate into effector Th cell subsets. The stability and plasticity of effector Th cells have not been well understood. In this study we used an IL-17F-red fluorescent protein reporter mouse to analyze the plasticity of Th17 cells in vitro and in vivo. We found that in vitro generated Th17 cells poorly maintained their differentiation program in vitro and could be reprogrammed into other T cell lineages. Moreover, upon transfer into lymphopenic hosts, Th17 cells rapidly lost their IL-17 expression and were converted into Th1 cells independently of IL-7 signaling. However, Th17 cells maintained their phenotypes well in normal animals, even in the absence of Ag and inflammation. These results, although suggesting the plasticity of Th17 cells, also indicate active maintenance of their program in vivo.

CCR6 regulates the migration of inflammatory and regulatory T cells

Th17 and regulatory T (Treg) cells play opposite roles in autoimmune diseases. However, the mechanisms underlying their proper migration to inflammatory tissues are unclear. In this study, we report that these two T cell subsets both express CCR6. CCR6 expression in Th17 cells is regulated by TGF-beta and requires two nuclear receptors, RORalpha and RORgamma. Th17 cells also express the CCR6 ligand CCL20, which is induced synergistically by TGF-beta and IL-6, which requires STAT3, RORgamma and IL-21. Th17 cells, by producing CCL20, promote migration of Th17 and Treg cells in vitro in a CCR6-dependent manner. Lack of CCR6 in Th17 cells reduces the severity of experimental autoimmune encephalomyelitis and Th17 and Treg recruitment into inflammatory tissues. Similarly, CCR6 on Treg cells is also important for their recruitment into inflammatory tissues. Our data indicate an important role of CCR6 in Treg and Th17 cell migration.

A critical role of costimulation during intrathymic development of invariant NK T cells

CD1d-restricted Valpha14(+) invariant NK T (iNKT) cells are a specialized alphabeta T cell subset that regulates both innate and adaptive immunity. Although costimulatory molecules are required for the activation of conventional T cells and for the development of Foxp3(+) T cells, their role in iNKT cell regulation is unclear. Here we report that mice deficient in CD80/CD86 and/or B7h exhibit severe defects in thymic iNKT cell maturation, associated with largely reduced iNKT cell number in the thymus and the periphery. We show that costimulation is necessary for the optimal expansion of postselected NK1.1(-) immature iNKT cells in the thymus and for the proper expression of the maturation markers T-bet and CD122. Surprisingly, costimulatory molecules on both hemopoietic and nonhematopoietic cells are required for iNKT cell development. Our results thus demonstrate a previously unknown function of costimulation in the intrathymic development of iNKT cells, distinct from that of conventional T cells and regulatory T cells.

Regulation of inflammatory responses by IL-17F

Although interleukin (IL) 17 has been extensively characterized, the function of IL-17F, which has an expression pattern regulated similarly to IL-17, is poorly understood. We show that like IL-17, IL-17F regulates proinflammatory gene expression in vitro, and this requires IL-17 receptor A, tumor necrosis factor receptor-associated factor 6, and Act1. In vivo, overexpression of IL-17F in lung epithelium led to infiltration of lymphocytes and macrophages and mucus hyperplasia, similar to observations made in IL-17 transgenic mice. To further understand the function of IL-17F, we generated and analyzed mice deficient in IL-17F or IL-17. IL-17, but not IL-17F, was required for the initiation of experimental autoimmune encephalomyelitis. Mice deficient in IL-17F, but not IL-17, had defective airway neutrophilia in response to allergen challenge. Moreover, in an asthma model, although IL-17 deficiency reduced T helper type 2 responses, IL-17F-deficient mice displayed enhanced type 2 cytokine production and eosinophil function. In addition, IL-17F deficiency resulted in reduced colitis caused by dextran sulfate sodium, whereas IL-17 knockout mice developed more severe disease. Our results thus demonstrate that IL-17F is an important regulator of inflammatory responses that seems to function differently than IL-17 in immune responses and diseases.