Th17 Plasticity Research Articles

Changing behind the scenes.

Th17 cell plasticity is associated with pathogenicity in chronic inflammation. In a model of periodontitis, McClure et al. (https://doi.org/10.1084/jem.20232015) describe location-dependent divergence in Th17 plasticity, with surprisingly limited conversion in inflamed gingiva but emergence of protective exTh17-TfH cells in draining LN that enhance protective antibody.

Venetoclax Induces BCL-2-Dependent Treg to TH17 Plasticity to Enhance the Antitumor Efficacy of Anti-PD-1 Checkpoint Blockade.

The specific BCL-2 small molecule inhibitor venetoclax induces apoptosis in a wide range of malignancies, which has led to rapid clinical expansion in its use alone and in combination with chemotherapy and immune-based therapies against a myriad of cancer types. While lymphocytes, and T cells in particular, rely heavily on BCL-2 for survival and function, the effects of small molecule blockade of the BCL-2 family on surviving immune cells is not fully understood. We aimed to better understand the effect of systemic treatment with venetoclax on regulatory T cells (Treg), which are relatively resistant to cell death induced by specific drugging of BCL-2 compared to other T cells. We found that BCL-2 blockade altered Treg transcriptional profiles and mediated Treg plasticity toward a TH17-like Treg phenotype, resulting in increased IL17A production in lymphoid organs and within the tumor microenvironment. Aligned with previously described augmented antitumor effects observed when combining venetoclax with anti-PD-1 checkpoint inhibition, we also demonstrated that Treg-specific genetic BCL-2 knockout combined with anti-PD-1 induced tumor regression and conferred overlapping genetic changes with venetoclax-treated Tregs. As long-term combination therapies using venetoclax gain more traction in the clinic, an improved understanding of the immune-modulatory effects caused by venetoclax may allow expansion of its use against malignancies and immune-related diseases.

Patched 1 and C-C Motif Chemokine Receptor 6 Distinguish Heterogeneous T Helper 17 Subsets in Colitic Lamina Propria

ABSTRACT T helper 17 (Th17) cells contribute to the pathogenesis of inflammatory bowel diseases (IBD). However, their heterogeneity and regulatory mechanisms in IBD are not completely disclosed. A mouse colitis model was established. Th17 cells were enriched from the mesenteric lymph nodes (mLN) and lamina propria (LP). The phenotypes and functions of Th17 subsets were analyzed by flow cytometry, Immunoblotting, and real-time RT-PCR. The contributions of the Th17 subsets to colitis pathogenesis were evaluated by histology, ELISA, and flow cytometry after adoptive transfer. Smoothened (SMO), GLI family zinc finger 1 (Gli1), and GLI family zinc finger 3 (Gli3) were markedly up-regulated while Patched 1 (PTCH1) was down-regulated in LP Th17 cells in colitic lamina propria. Based on the expression of PTCH1 and C-C motif chemokine receptor 6 (CCR6), LP Th17 cells were divided into a PTCH1lowCCR6low Th17 subset and a PTCH1highCCR6high Th17 subset. The former expressed higher T-bet, IFN-γ, TNF-α, IL-1β, and GM-CSF but lower IL-17A, IL-22, IL-17F, and Gli3 than the latter. The PTCH1highCCR6high Th17 subset was more resistant to polarization towards T helper 1 (Th1) than the PTCH1lowCCR6low Th17 subset. Moreover, the PTCH1highCCR6high Th17 subset was more competent to maintain Th17 identity. The PTCH1highCCR6high Th17 subset induced less severe colitis than the PTCH1lowCCR6low Th17 subset. PTCH1highCCR6high Th17 cells are Th17 cells whereas PTCH1lowCCR6low Th17 cells are Th1-like Th17 cells. Our study deepens the understanding of Th17 heterogeneity and plasticity in colitis.

Deep Insight into the Role of MIF in Spondyloarthritis.

Pathological roles of macrophage migration inhibitory factor (MIF) have recently been demonstrated in spondyloarthritis (SpA) preclinical models, identifying MIF as a new treatment target for SpA. However, the specific contribution of MIF and therapeutic potential of MIF-targeted therapies to various tissue types affected by SpA are not well delineated. MIF and its cognate receptor CD74 are extensively involved in the pathogenesis of SpA including inflammation in the spine, joint, eyes, skin, and gut. The majority of the current evidence has consistently shown that MIF drives the inflammation in these distinct anatomical sites. In preclinical models, genetic deletion or blockade of MIF reduces the severity of inflammation. Although MIF is generally an upstream cytokine which regulates downstream effector cytokines, MIF also intensifies type 3 immunity by promoting helper T 17 (Th17) plasticity. MIF- or CD74-targeted therapies have also reported to be well tolerated in clinical trials for other diseases. Recent findings suggest that MIF-CD74 axis is a new therapeutic target for SpA to improve various clinical features. Clinical trials for MIF- or CD74-targeted therapies for SpA patients are warranted.

The Tyrosine Kinase Tec Regulates Effector Th17 Differentiation, Pathogenicity, and Plasticity in T-Cell-Driven Intestinal Inflammation.

T helper (Th) 17 cells are not only key in controlling infections mediated by extracellular bacteria and fungi but are also triggering autoimmune responses. Th17 cells comprise heterogeneous subsets, some with pathogenic functions. They can cease to secrete their hallmark cytokine IL-17A and even convert to other T helper lineages, a process known as transdifferentiation relying on plasticity. Both pathogenicity and plasticity are tightly linked to IL-23 signaling. Here, we show that the protein tyrosine kinase Tec is highly induced in Th17 cells. Th17 differentiation was enhanced at low interleukin-6 (IL-6) concentrations in absence of Tec, which correlates with increased STAT3 phosphorylation and higher Il23r expression. Therefore, we uncovered a function for Tec in the IL-6 sensing via STAT3 by CD4+ T cells, defining Tec as a fine-tuning negative regulator of Th17 differentiation. Subsequently, by using the IL-17A fate mapping mouse combined with in vivo adoptive transfer models, we demonstrated that Tec not only restrained effector Th17 differentiation but also pathogenicity and plasticity in a T-cell intrinsic manner. Our data further suggest that Tec regulates inflammatory Th17-driven immune responses directly impacting disease severity in a T-cell-driven colitis model. Notably, consistent with the in vitro findings, elevated levels of the IL-23 receptor (IL-23R) were observed on intestinal pre- and postconversion Th17 cells isolated from diseased Tec−/− mice subjected to adoptive transfer colitis, highlighting a fundamental role of Tec in restraining IL-23R expression, likely via the IL-6-STAT3 signaling axis. Taken together, these findings identify Tec as a negative regulator of Th17 differentiation, pathogenicity, and plasticity, contributing to the mechanisms which help T cells to orchestrate optimal immune protection and to restrain immunopathology.

Interleukin-6 receptor alpha and CD27 discriminate intratumoral T helper 17 subpopulations with distinct functional properties in a mouse lung cancer model.

BackgroundT helper 17 (Th17) cells actively participate in the tumor immune response in lung cancer. However, the heterogeneity and plasticity of intratumoral Th17 cells in lung cancer remain elusive. In this study, Th17 subpopulations were characterized in a mouse lung cancer model.MethodsUrethane was administered to induce lung cancer in interleukin (IL)‐17‐EGFP transgenic mice. Flow cytometry was used to analyze the phenotypes, signaling status, and functions of Th17 subpopulations either in vivo or in vitro. The adoptive transfer assay and real‐time polymerase chain reaction were applied to analyze the plasticity of Th17 subpopulations.ResultsIL‐6RαhighCD27− Th17 and IL‐6RαlowCD27+ Th17 were identified in intratumoral Th17 cells. The two subpopulations expressed equivalent RORγt. However, the former expressed higher T‐bet but lower Foxp3, more IL‐17A and IFN‐γ but less IL‐10 than the latter. Furthermore, IL‐6RαhighCD27− Th17 moderately inhibited the proliferation of lung cancer cells while IL‐6RαlowCD27+ Th17 could not. IL‐6RαhighCD27− Th17 exhibited weaker Jun N‐terminal kinases (JNK) signaling but stronger signal transducer and activator of transcription 3 (Stat3) signaling than IL‐6RαlowCD27+ Th17. The adoptive transfer assay indicated that both subpopulations downregulated RORγt in recipients' spleens but maintained RORγt in recipients' lungs. Meanwhile, IL‐6RαhighCD27− Th17 expressed higher T‐bet and IFN‐γ than IL‐6RαlowCD27+ Th17 in the recipients. IL‐6RαlowCD27+ Th17 expressed Foxp3 and IL‐10 in recipients' spleens but not lungs.ConclusionsThis study reveals intratumoral Th17 subpopulations with distinct functional properties and signaling patterns, thus offering valuable insight into Th17 heterogeneity and plasticity in lung cancer.

Single-cell clonotype tracing of tissue Th17 cells during CNS autoimmunity reveals the conversion of intestinal homeostatic cells to pathogenic cells

Abstract At homeostasis, most Th17 cells are found in the lamina propria of the intestine, where they contribute to tissue homeostasis by inhibiting microbiota from tissue invasion and promote barrier functions. Recent studies in humans and mice have implicated intestinal Th17 cells in extra-intestinal autoimmune diseases, including multiple sclerosis, but the mechanism in which intestinal Th17 cells mediate these dichotomous functions remains unknown. Here, we combined single-cell RNA- and TCR-seq (scRNA/TCR-seq) with fate mapping of tissue Th17 cells to profile over 84,000 tissue Th17 cells and characterize their heterogeneity, plasticity, and migration at homeostasis and during CNS autoimmunity. We discovered a homeostatic Th17 cell population, that is induced by the intestinal microbiota, is present in both lymphoid organs and the intestine, and expresses IL-17. Joint scRNA- and TCR-seq showed that during EAE this homeostatic population gives rise to a pathogenic Th17 cell population, that migrates specifically through the draining lymph nodes and the spleen to the CNS, and highly expresses GM-CSF and IFNγ, but expresses little or low levels of IL-17. This conversion of homeostatic Th17 cells into encephalitogenic Th17 cells depended on IL-23R signaling. Our work characterizes Th17 heterogeneity, plasticity, and migration during homeostasis and CNS autoimmune disease, identifies a mechanism by which intestinal Th17 cells influence the generation of an autoimmune disease-inducing population, and provides further evidence for a direct relationship between the IL-17-producing and GM-CSF- and IFNγ- producing pathogenic T cells.

Cytokine-regulated Th17 plasticity in human health and diseases.

Upon activation, naïve CD4+ T helper (Th) cells differentiate into distinct Th effector cell lineages depending on the local cytokine environment. However, these polarized Th cells can also adapt their function and phenotype depending on the changing cytokine environment, demonstrating functional plasticity. Here, Th17 cells, which play a critical role in host protection from extracellular pathogens and in autoimmune disorders, are of particular interest. While being able to shift phenotype within their lineage, Th17 cells can also acquire characteristics of Th1, Th2, T follicular helper (Tfh) or regulatory T cells. Th17 cell identity is determined by a spectrum of extracellular signals, including cytokines, which are critical orchestrators of cellular immune responses. Cytokine induces changes in epigenetic, transcriptional, translational and metabolomic parameters. How these signals are integrated to determine Th17 plasticity is not well defined, yet this is a crucial point of investigation as it represents a potential target to treat autoimmune and inflammatory diseases. The goal of this review was to discuss how cytokines regulate intracellular networks, focusing on the regulation of lineage-specific transcription factors, chromatin remodelling and metabolism, to control human Th17 cell plasticity. We discuss the importance of Th17 plasticity in autoimmunity and cancer and present current strategies and challenges in targeting pathogenic Th17 cells with cytokine-based approaches, considering human genetic variants associated with altered Th17 differentiation. Finally, we discuss how modulating Th17 plasticity rather than targeting the Th17 lineage as a whole might preserve its essential immune function while purging its adverse effects.

T-bet Expression in Peripheral Th17.0 Cells Is Associated With Pulmonary Function Changes in Sarcoidosis.

Background: Interferon-gamma (IFN-γ) is a key mediator of sarcoidosis-related granulomatous inflammation. Previous findings of IFN-γ-producing Th17 cells in bronchoalveolar lavage fluid from sarcoidosis patients invokes the transition of Th17.0 cells to Th17.1 cells in the disease's pathogenesis. Since the T-bet transcription factor is crucial for this transition, the goal of this study was to determine if T-bet expression in Th17.0 cells reflects the extent of granulomatous inflammation in sarcoidosis patients as assessed by clinical outcomes.Methods: Using a case-control study design, we identified two groups of sarcoidosis subjects (total N = 43) with pulmonary function tests (PFTs) that either (1) changed (increased or decreased) longitudinally or (2) were stable. We used flow cytometry to measure the transcription factors T-bet and RORγt in Th1, Th17.0, and Th17.1 cell subsets defined by CCR6, CCR4 and CXCR3 in blood samples. We compared the percentages of T-bet+ cells in RORγt+Th17.0 cells (defined as CCR6+CCR4+CXCR3−) based on subjects' PFT group. We also assessed the relationship between the direction of change in PFTs with the changes in %T-bet+ frequencies using mixed effects modeling.Results: We found that T-bet expression in subjects' RORγt+Th17.0 cells varied based on clinical outcome. The T-bet+ percentage of RORγt+Th17.0 cells was higher in the cases (subject group with PFT changes) as compared to controls (stable group) (27 vs. 16%, p = 0.0040). In comparisons before and after subjects' PFT changes, the T-bet+ frequency of RORγt+Th17.0 cells increased or decreased in the opposite direction of the PFT change. The percentage of these T-bet+ cells was also higher in those with greater numbers of involved organs. Serum levels of interferon-γ-induced chemokines, CXCL9, CXCL10, and CXCL11, and whole blood gene expression of IFN-γ-related genes including GBP1, TAP1, and JAK2 were independently positively associated with the T-bet+ frequencies of RORγt+Th17.0 cells.Conclusions: These data suggest that expression of T-bet in Th17.0 cells could reflect the extent of granulomatous inflammation in sarcoidosis patients because they represent a transition state leading to the Th17.1 cell phenotype. These findings indicate that Th17 plasticity may be part of the disease paradigm.

Biological and clinical significance of T helper 17 cell plasticity.

Mature T helper (Th) effector cells originate following antigen recognition by naive T precursors. The maturation process is accompanied by the acquisition of specific effector functions that distinguish at least three different T helper subsets: Th1, Th2 and Th17. In general, maturation of somatic cells is accompanied by terminal differentiation. However, accumulating evidence shows that effector T cells retain a certain degree of plasticity. This is especially true for Th17 cells, which have been shown to converge towards other phenotypes in response to specific microenvironmental pressure. In this review we will discuss the experimental evidence that supports the hypothesis of Th17 plasticity, with particular emphasis on the generation of Th17-derived 'non-classic' Th1 cells, and the molecular networks that control it. Moreover, we will consider why Th17 plasticity is important for host protection, but also why it can have pathogenic functions during chronic inflammation. Regarding the last point, we will discuss a possible role for biological drugs in the control of Th17 plasticity and disease course.

Differential Pathogenic Th17 Profile in Mesenteric Lymph Nodes of Crohn's Disease and Ulcerative Colitis Patients.

The drug targets IL23 and IL12 regulate pathogenicity and plasticity of intestinal Th17 cells in Crohn's disease (CD) and ulcerative colitis (UC), the two most common inflammatory bowel diseases (IBD). However, studies examining Th17 dysregulation in mesenteric lymph nodes (mLNs) of these patients are rare. We showed that in mLNs, CD could be distinguished from UC by increased frequencies of CCR6+CXCR3−RORγ+Tbet−CD4+ (Th17) memory T cells enriched in CD62Llow effector memory T cells (TEM), and their differentially expressed molecular profile. Th17 TEM cells (expressing IL17A, IL17F, RORC, and STAT3) displayed a higher pathogenic/cytotoxic (IL23R, IL18RAP, and GZMB, CD160, PRF1) gene signature in CD relative to UC, while non-pathogenic/regulatory genes (IL9, FOXP3, CTLA4) were more elevated in UC. In both CD and UC, IL12 but not IL23, augmented IFNγ expression in Th17 TEM and switched their molecular profile toward an ex-Th17 (Th1*)-biased transcriptomic signature (increased IFNG, and decreased TCF7, IL17A), suggesting that Th17 plasticity occurs in mLNs before their recruitment to inflamed colon. We propose that differences observed between Th17 cell frequencies and their molecular profile in CD and UC might have implications in understanding disease pathogenesis, and thus, therapeutic management of patients with IBD.

Th17 and Th1 Lymphocytes in Oligoarticular Juvenile Idiopathic Arthritis.

In the last years much attention has focused on the Th17 and Th1 phenotypes and on their pathogenic role in juvenile idiopathic arthritis, investigating how the cytokines produced by T helper cells act on resident cells on the synovia and which signal transduction pathways regulate Th17 cells proliferation and plasticity. In this context, an important milestone was represented by the identification of the non-classic Th1 phenotype, developed from the shift of Th17 cells. The cytokine TNF-α, beyond its well-known proinflammatory activity is involved in this process and this is one of the reasons why the TNF-α inhibitors are widely used in the treatment of juvenile idiopathic arthritis patients.

Association of synovial tissue polyfunctional T-cells with DAPSA in psoriatic arthritis

ObjectiveThis study examines polyfunctional T-cells in psoriatic arthritis (PsA) synovial tissue and their associations with clinical disease and implications for therapy.MethodsPsA synovial tissue was enzymatically/mechanically digested to generate synovial tissue...

The role of transforming growth factor β in T helper 17 differentiation.

T helper 17 (Th17) cells play critical roles in inflammatory and autoimmune diseases. The lineage-specific transcription factor RORγt is the key regulator for Th17 cell fate commitment. A substantial number of studies have established the importance of transforming growth factor β (TGF-β) -dependent pathways in inducing RORγt expression and Th17 differentiation. TGF-β superfamily members TGF-β1 , TGF-β3 or activin A, in concert with interleukin-6 or interleukin-21, differentiate naive T cells into Th17 cells. Alternatively, Th17 differentiation can occur through TGF-β-independent pathways. However, the mechanism of how TGF-β-dependent and TGF-β-independent pathways control Th17 differentiation remains controversial. This review focuses on the perplexing role of TGF-β in Th17 differentiation, depicts the requirement of TGF-β for Th17 development, and underscores the multiple mechanisms underlying TGF-β-promoted Th17 generation, pathogenicity and plasticity. With new insights and comprehension from recent findings, this review specifically tackles the involvement of the canonical TGF-β signalling components, SMAD2, SMAD3 and SMAD4, summarizes diverse SMAD-independent mechanisms, and highlights the importance of TGF-β signalling in balancing the reciprocal conversion of Th17 and regulatory T cells. Finally, this review includes discussions and perspectives and raises important mechanistic questions about the role of TGF-β in Th17 generation and function.

Regulatory action of multiple AP-1 transcription factors balances Th17 lineage stability and plasticity

Abstract During an immune response, naïve CD4+ T cells encounter their cognate antigen and are induced to differentiate into one of several distinct T helper (Th) subsets. Although previously regarded as lineage-committed, these differentiated subsets are now appreciated to exhibit a degree of plasticity, whereby certain environmental stimuli permit inter-subset conversion. In particular, Th17 cells have been demonstrated to exhibit a high degree of intrinsic plasticity and are capable of “reprogramming” towards phenotypes typical of both pro- and anti-inflammatory T cell subsets. Despite the suggested importance of this phenomenon in the etiology of autoimmune and inflammatory disorders, the mechanisms underlying Th17 cell plasticity are poorly understood. We have recently identified the AP-1 transcription factor family as a central controller of both Th17 cell stability and plasticity, with different AP-1 family members exhibiting both overlapping and unique control of distinct aspects of the Th17 transcriptional program. Using a combined strategy employing transcriptomics and global analysis of TF occupancy for multiple AP-1 family members, we have identified novel regulatory modules defined by distinct modes of AP-1-mediated activation. These findings provide new insights into the mechanism by which environmentally-regulated transcription factors collaborate for the maintenance of T cell identity.

Cellular and Molecular Dynamics of Th17 Differentiation and its Developmental Plasticity in the Intestinal Immune Response.

After emerging from the thymus, naive CD4 T cells circulate through secondary lymphoid tissues, including gut-associated lymphoid tissue of the intestine. The activation of naïve CD4 T cells by antigen-presenting cells offering cognate antigen initiate differentiation programs that lead to the development of highly specialized T helper (Th) cell lineages. Although initially believed that developmental programing of effector T cells such as T helper 1 (Th1) or T helper 2 (Th2) resulted in irreversible commitment to a fixed fate, subsequent studies have demonstrated greater flexibility, or plasticity, in effector T cell stability than originally conceived. This is particularly so for the Th17 subset, differentiation of which is a highly dynamic process with overlapping developmental axes with inducible regulatory T (iTreg), T helper 22 (Th22), and Th1 cells. Accordingly, intermediary stages of Th17 cells are found in various tissues, which co-express lineage-specific transcription factor(s) or cytokine(s) of developmentally related CD4 T cell subsets. A highly specialized tissue like that of the intestine, which harbors the largest immune compartment of the body, adds several layers of complexity to the intricate process of Th differentiation. Due to constant exposure to millions of commensal microbes and periodic exposure to pathogens, the intestinal mucosa maintains a delicate balance between regulatory and effector T cells. It is becoming increasingly clear that equilibrium between tolerogenic and inflammatory axes is maintained in the intestine by shuttling the flexible genetic programming of a developing CD4 T cell along the developmental axis of iTreg, Th17, Th22, and Th1 subsets. Currently, Th17 plasticity remains an unresolved concern in the field of clinical research as targeting Th17 cells to cure immune-mediated disease might also target its related subsets. In this review, we discuss the expanding sphere of Th17 plasticity through its shared developmental axes with related cellular subsets such as Th22, Th1, and iTreg in the context of intestinal inflammation and also examine the molecular and epigenetic features of Th17 cells that mediate these overlapping developmental programs.

Th17 plasticity and transition toward a pathogenic cytokine signature are regulated by cyclosporine after allogeneic SCT

AbstractT-helper 17 (Th17) cells have been widely implicated as drivers of autoimmune disease. In particular, Th17 cytokine plasticity and acquisition of an interleukin-17A+(IL-17A+)interferon γ(IFNγ)+ cytokine profile is associated with increased pathogenic capacity. Donor Th17 polarization is known to exacerbate graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (allo-SCT); however, donor Th17 cytokine coexpression and plasticity have not been fully characterized. Using IL-17 “fate-mapping” mice, we identified IL-6-dependent Th17 cells early after allo-SCT, characterized by elevated expression of proinflammatory cytokines, IL-17A, IL-22, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor. This population did not maintain lineage fidelity, with a marked loss of IL-17A and IL-22 expression late posttransplant. Th17 cells were further segregated based on IFNγ coexpression, and IL-17A+IFNγ+ Th17 displayed an enhanced proinflammatory phenotype. Th17 cytokine plasticity and IFNγ production were critically dependent upon donor-derived IL-12p40, and cyclosporine (CsA) treatment regulated this differentiation pathway. This observation was highly concordant with clinical samples from allo-SCT recipients receiving CsA-based immune suppression where although the IFNγ-negative–Th17 subset predominated, IFNγ+-Th17 cells were also present. In sum, Th17 polarization and ensuing differentiation are mediated by sequential inflammatory signals, which are modulated by immunosuppressive therapy, leading to distinct phenotypes within this lineage.

The role of AP-1 family transcription factor networks in regulating Th17 cell identity

Abstract CD4 T cells can adopt one of two opposing fates: a helper T cell (Th) specialized in supporting pathogen clearance, or a regulatory T cell (Treg) that attenuates immune responses. IL-17A-producing inflammatory Th17 cells stand out among Th cells, possessing a high level of inherent plasticity in response to altered environments. The underlying mechanisms controlling such flexibility are largely unknown. In this regard, we have identified the AP-1 family of transcription factors (TFs) as key regulators of Th17 cell identity. Our previous work revealed the pioneering role of BATF in supporting global enhancer accessibility and flexibility in CD4 T cells, and here, we describe an antagonistic AP-1 TF, JunB, that limits Th17 plasticity. Indeed, we find that CD4 T cells deficient in JunB exhibit dysregulated effector cytokine and TF expression signatures, and lack disease potential in a mouse model of autoimmunity. In particular, JunB serves to restrain inappropriate Treg and Th1 differentiation. Here, we (i) use fate-mapping reporter mice to dissect the requirement for JunB in maintaining Th17 cell stability, (ii) define the JunB targets that facilitate subset conversion events; (iii) define novel genomic lineage-restriction elements regulated by AP-1 complexes; and (iv) define activating and repressing roles of JunB that support Th17 lineage stability. Such mechanistic insight is key to guiding future work aimed at exploiting the AP-1 balance in Th17 cells to divert damaging inflammatory responses into favorable regulatory responses.

Th Cell Diversity in Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis.

Multiple sclerosis (MS) is believed to be initiated by myelin-reactive CD4(+) Th cells. IL-12-polarized Th1 cells, IL-23-polarized Th17 cells, and Th17 cells that acquire Th1 characteristics were each implicated in autoimmune pathogenesis. It is debated whether Th cells that can drive the development of demyelinating lesions are phenotypically diverse or arise from a single lineage. In the current study, we assessed the requirement of IL-12 or IL-23 stimulation, as well as Th plasticity, for the differentiation of T cells capable of inducing CNS axon damage. We found that stable murine Th1 and Th17 cells independently transfer experimental autoimmune encephalomyelitis (widely used as an animal model of MS) in the absence of IL-23 and IL-12, respectively. Plastic Th17 cells are particularly potent mediators of demyelination and axonopathy. In parallel studies, we identified MS patients who consistently mount either IFN-γ- or IL-17-skewed responses to myelin basic protein over the course of a year. Brain magnetic resonance imaging revealed that patients with mixed IFN-γ and IL-17 responses have relatively high T1 lesion burden, a measure of permanent axon damage. Our data challenge the dogma that IL-23 and Th17 plasticity are universally required for the development of experimental autoimmune encephalomyelitis. This study definitively demonstrates that autoimmune demyelinating disease can be driven by distinct Th-polarizing factors and effector subsets, underscoring the importance of a customized approach to the pharmaceutical management of MS.

Sa1758 In Vitro Adalimumab Exposure Decreases RORγT Expressing and RORγT/FoxP3 Double Expressing T-Lymphocytes From Peripheral Blood of Crohn's Disease Patients: A Study of Th17 Plasticity in Response to Anti-TNF

G A A b st ra ct s recognizing E. coli OmpC. Methods: Tetramer-guided epitope mapping (TGEM) in HLADR*1501 subjects consistently identified a single T cell epitope in OmpC for use in tetramerbased assays. Direct ex vivo characterization was performed by staining with PE-labeled tetramers against OmpC and Flu peptides and subsequent enrichment with anti-PE magnetic beads. Cells were stained for surface markers and analyzed by flow cytometry. Frequency of antigen-specific T cells was calculated as the number of post-enrichment tetramer+ cells/ total pre-enrichment CD4+ cells. Results: The frequency of OmpC-specific T cells was 9.1 (+/-2)/million CD4+ T cells (n=26) compared to 13.7 (+/-2)/million Flu-specific T cells (n= 17), p=.18. The majority of both Flu and OmpC-specific T cells expressed a memory T cell phenotype (CD45RA-). There were no regulatory T cells (CD25+CD127-) identified among OmpC or Flu-specific CD4s. A high percentage of OmpC-specific T cells expressed the guthoming marker, a4b7, compared to Flu-specific T cells (44%+/-2 vs. 13.7% +/-2, p<.0001). Expression of the Th17 marker, CD161, was more frequent on OmpC than Flu-specific T cells (38.5 %+/-5 vs. 13% +/-2, p <.0001). While there was some expression of the Th1 marker, CXCR3, on OmpC-specific T cells, this was less than was expressed by Flu-specific T cells (27%+/-4 vs. 50% +/-5, p= .0015). The current study was underpowered to detect differences in frequency or phenotype among OmpC seropositive and seronegative CD subjects and healthy controls. OmpC-specific T cells identified above were isolated for future RNA transcript analyses to reveal qualitative differences in these cells between patients with and without CD. Conclusions: We have identified T cell epitopes for E.coli OmpC in HLADR *1501 subjects and generated MHC class II tetramers that identify OmpC-specific T cells. OmpC-specific T cells have a frequency similar to Flu-specific T cells and bear a distinct phenotype. They are memory T cells with gut-homing integrin a4b7 expression. They lack Treg markers and express mixed Th1 and Th17 markers. These data confirm that healthy humans and CD subjects harbor commensal-specific T cells and suggest that active suppression of T cell responses is lost in subjects with CD.