Immunity

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is caused by impaired central immune tolerance due to deficiency of the Autoimmune Regulator (AIRE) and is characterized by severe, multiorgan autoimmunity. We recently identified interferon-{gamma} (IFN-{gamma}) as a dominant driver of immunopathology in APECED and showed that treatment with the JAK1/2 inhibitor ruxolitinib ameliorates disease in both AIRE-deficient mice and patients. However, broad JAK inhibition is associated with clinically relevant toxicities, raising the question of whether selective targeting of individual JAK pathways can retain efficacy while sparing nonpathogenic immune programs. Here, we systematically evaluated the effects of selective JAK1, JAK2, and JAK3 inhibition in Aire-/- mice. Selective JAK1 and JAK2 inhibition reduced autoimmune tissue injury, suppressed IFN-{gamma} signaling, and decreased accumulation of pathogenic T cells, with JAK2 inhibition providing the most robust protection, comparable to ruxolitinib. In contrast, selective JAK3 inhibition decreased T cell accumulation, but paradoxically increased the proportion of IFN-{gamma}-producing T cells and did not significantly attenuate IFN-{gamma}-driven tissue inflammation. These findings reveal an unexpected uncoupling between lymphocyte burden and pathogenic cytokine bias and identify IFN-{gamma} signaling as hierarchically dominant over {gamma}c-dependent pathways in AIRE deficiency. Together, our data indicate that effective control of APECED-associated autoimmunity requires direct suppression of the IFN-{gamma}-JAK2 axis rather than generalized lymphocyte inhibition and suggest that selective JAK2 targeting may represent a rational strategy to preserve therapeutic efficacy while minimizing disruption of JAK1-and {gamma}c-dependent immune functions.

Targeting Tregs is a potential strategy to improve cancer therapies. However, which Tregs accumulate in response to tumoral processes, and how tumors affect their phenotype, is poorly understood. Here we show that tumor Tregs are equivalent to effector tissue Tregs in steady state organs. We used a mouse model of intestinal neoplasia to demonstrate that one early event in carcinogenesis is sufficient to induce local accumulation of Tregs resembling human tumor Tregs. Treg accumulation was driven by TCR-dependent oligoclonal expansion of tissue Tregs with an effector Treg phenotype. Treg expansion was independent of CCR8, IL33R and CD137, which were previously linked to tumor Treg. In contrast, GATA3 was required for effector tissue Tregs and for their expansion in response to neoplasia. Our findings identify GATA3-dependent clonal expansion of effector tissue Tregs as a key event in promoting tumor growth. HighlightsO_LIAn early tumorigenic event alone drives accumulation of effector tissue Tregs C_LIO_LITregs in tumors are phenotypically akin to effector tissue Tregs C_LIO_LIThe accumulation of Tregs is driven by TCR-dependent oligoclonal expansion C_LIO_LIGATA3 controls tumor-promoting effector tissue Tregs C_LI

The gastrointestinal tract is a unique immunological environment where the host must balance tolerance to commensal microbes with defense against pathogens. A critical mechanism for maintaining this balance is the peripheral conversion of naive T cells into regulatory T cells (pTregs), a process that depends on the TGF-{beta} cytokine, which is produced in a latent form and must be activated. While the activation of latent TGF-{beta} relies on the membrane-bound v{beta}8 integrin, the precise cellular subset(s) responsible for this essential process have yet to be clearly defined. Conventional dendritic cells (cDCs), which migrate from the intestinal lamina propria to the gut-draining mesenteric lymph nodes (MLN), have long been considered the primary antigen-presenting cells (APCs) responsible for v{beta}8-mediated TGF-{beta} activation and pTreg induction. However, recent studies have challenged this paradigm by highlighting a new family of rare ROR{gamma}t-expressing APCs, able to induce pTreg via v integrins, raising questions about the in vivo role of cDCs in the maintenance of mucosal immune homeostasis. Using a {beta}8 integrin gene reporter mouse model (Itgb8-IRES-tdTomato) combined with single-cell profiling, we comprehensively mapped Itgb8-expressing APCs in the MLN. We show that cDCs, in particular migratory type 1 (cDC1) and type 2 (cDC2), constitute the predominant Itgb8TdTomato+ cells, both in neonatal and adult mice. Through cDC subset-specific {beta}8 knockout models, we demonstrate that both cDC1 and cDC2 are required for optimal pTreg generation. Loss of {beta}8 integrin in either subset led to a partial reduction in pTreg, while combined deletion resulted in profound pTreg loss and spontaneous colitis. Importantly, these effects were independent of ROR{gamma}t APC populations, including ILC3s and Thetis cells. These findings resolve longstanding questions about the identity of key APCs driving pTreg induction in the MLNs. They demonstrate that cDC1 and cDC2 are non-redundant, essential mediators of pTreg induction and intestinal immune tolerance. Although different populations of ROR{gamma}t APCs may contribute in specific contexts, such as early development, infection, or in the prevention of allergic disease, cDCs remain one of the primary guardians of intestinal immune homeostasis in response to microbiota.

Chronic innate immune activation is widely thought to challenge self-tolerance. IL-18 is an inflammasome-activated cytokine and potent amplifier of T-cell activation whose excess is associated with certain autoinflammatory, but not autoimmune, diseases. We tested how excess IL-18 affected susceptibility to experimental autoimmune encephalomyelitis (EAE), a model of CNS autoimmunity driven by IL-18 responsive, myelin-autoreactive CD4 T-cells (CD4Tauto). We hypothesized that IL-18 would exacerbate immunopathology in EAE. Instead, excess IL-18 was profoundly protective. IL-18 did not impair CD4Tauto priming or early expansion. Rather, it selectively restricted later accumulation of highly activated, splenic CD4Tauto bearing CNS-homing integrins. Despite high IL-18 receptor expression on CD4Tauto and Foxp3+ CD4Treg, excess IL-18 acted specifically through mature CD8 T-cells to promote a highly activated CD8Teffector phenotype and IFN{gamma}-dependent protection from EAE. Therapeutic administration of a "decoy-resistant" IL-18 agonist (DR-18) to wild-type mice, even after CD4Tauto expansion, nevertheless engaged CD8 T-cells to diminish CD4Tauto abundance, prevent CNS infiltration, and block immunopathology. Together, these findings demonstrate IL-18s unexpected, dominant ability to mobilize protective CD8 T-cells against highly activated CD4Tauto and protect from CNS autoimmune pathology; illustrating a potential therapeutically relevant mechanism by which autoinflammation actively opposes autoimmunity.

Interferon regulatory factor 1 (IRF1), a transcription factor encoded within the 5q31 locus harboring systemic lupus erythematosus (SLE) associated variants, promotes inflammatory responses by T and myeloid cells. Although IFN{gamma}-activated B cells also express IRF1, its role in B cell biology and SLE is unclear. Here, we use a mouse SLE model, single-cell multiomics, and human B cells to show that IRF1 intrinsically regulates Irf4 gene chromatin accessibility and expression in B cells to control the balance between the antibody secreting cell (ASC) lineage commitment factor, IRF4, and the B cell identity factor, IRF8. We demonstrate that IRF1, through its integration of IFN{gamma} and TLR7 induced transcriptional programs, tips B cells toward a terminal effector inflammatory AC fate at the expense of preserving more stem-like, resting and regulatory B cells that do not elicit autoantibody-associated pathology in SLE. Thus, IRF1 serves as a central node controlling B cell-driven autoimmune disease.

Resident memory T cells (TRM) mediate localized immunity in barrier tissues while central memory T cells (TCM) recirculate through lymphoid organs to surveil for reinfection. Although TRM are classically associated with peripheral non-lymphoid tissues, they have also been identified within lymph nodes (LNRM) where the mechanisms guiding their formation and functional differences remain poorly understood. Here we used longitudinal antibody labeling to track the migratory history of memory T cells after influenza infection and demonstrate that CD69+CD103+ T cells are resident in the lymph node. LNRM accumulate evenly throughout the lung-draining lymph node and are present within all analyzed LN compartments including, the sub capsular sinus, T cell zone and germinal centers. Epigenetic and transcriptional profiling reveal that LNRM are uniquely poised for cytotoxicity whereas TRM in the lung (LungRM) resemble exhausted cells with elevated expression of inhibitory receptors and increased chromatin accessibility at the Pdcd1 locus. Regulatory network analysis of transcription factors, combined with target gene expression and chromatin accessibility, identified key regulons differentiating TCM, LNRM and LungRM states. Upon antigen re-encounter, LNRM are more proliferative, cytotoxic, and produce more IFN{gamma} compared to LungRM. Notably, we find that LNRM represent the most prevalent subset of memory T cells in human thoracic lymph nodes. These findings highlight functional heterogeneity in TRM and establish LNRM as a distinct and durable memory T cell population bridging features of circulating and tissue-resident cells.

Summary paragraphMultiple sclerosis (MS) is a chronic autoimmune disease targeting the central nervous system (CNS). MS develops almost exclusively in individuals previously infected with Epstein-Barr virus (EBV)1, yet the mechanisms linking EBV infection to MS pathogenesis remain incompletely defined. Here we characterized EBV-infected B cells in MS and demonstrated that EBV directly infects autoreactive anti-CNS antigen B cells and reprograms them into pro-inflammatory antigen-presenting cells (APCs). EBV B cells in MS were enriched within the CD27CD21low memory B-cell subset and exhibited upregulated B cell activation and APC transcriptional programs. Recombinant antibodies derived from MS blood and cerebrospinal fluid (CSF) EBV B cells bound brain tissue, and several cross-bound both MS-associated autoantigens and Epstein-Barr virus nuclear antigen-1 (EBNA1). In vitro, EBV B cells functioned as APCs that stimulated T peripheral helper cells, with associated activation of EBV- anti-CNS antigen B cells. Collectively, these findings support a mechanistic framework in which EBV infects and transcriptionally reprograms autoreactive anti-CNS antigen B cells into APCs that drive pathogenic anti-CNS antigen T cell and EBV- B cell responses in MS.

Dendritic cells (DCs) are critical for initiating adaptive immunity through antigen presentation and T cell priming. While immunogenic cell death (ICD) enhances anti-tumor immunity, how programmed cell death in DCs shapes tumor immune responses remains unclear. Receptor-interacting protein kinase 1 (RIPK1) regulates apoptosis, necroptosis, and inflammation. Here, we show that mice with disrupted RIPK1 ubiquitination on K376 (Ripk1fl/K376R Cd11c-Cre, Ripk1DC-KO/K376R) develop inflammation and autoimmunity, phenocopying DC-specific RIPK1-deficient(Ripk1fl/fl Cd11c-Cre, Ripk1DC-KO) mice. These phenotypes were rescued by the genetic ablation of Ripk3 or Mlkl, establishing that RIPK1 ubiquitination is essential for suppressing DC necroptosis to maintain immune homeostasis. Remarkably, both Ripk1DC-KO and Ripk1DC-KO/K376R mice exhibit robust resistance to tumor growth, characterized by significantly enhanced T cell infiltration and activation. Mechanistically, we show that Ripk1 deficiency or the loss of its K376 ubiquitination augments antigen-presenting capacity of DCs through both necroptosis-dependent and -independent pathways. Furthermore, adoptive transfer of T cells from Ripk1DC-KO mice further amplifies anti-tumor immunity in recipient hosts. These results identify RIPK1 as a critical immunological checkpoint in DCs that constrains their immunogenic potential. Targeting this pathway represents a promising therapeutic strategy to potentiate T cell-mediated cancer immunotherapy.

Variants in TNFAIP3 (encoding A20) are among the most consistent non-MHC genetic associations with human autoimmune disease. Moreover, TNFAIP3 haploinsufficiency confers an autosomal dominant autoinflammatory and autoimmune disease. Whilst these findings strongly suggest that quantitative changes in A20 predispose to pathology, there is currently no evidence that post-transcriptional modifications regulate A20 abundance. We used human reverse genetics approach to investigate this question. From a cohort of patients with complex immune diseases, we identified an ultrarare hypomorphic TNFAIP3 variant (A20S254R) that is both hypomorphic and prone to phosphorylation. One of five carriers of this variant was distinguished by autoimmunity and an NF-kB gain-of-function transcriptional signature. A search for modifiers identified a variant in TAX1BP1 (p.Leu207Ile). We discovered that TAX1BP1 normally retrains A20 phosphorylation. Furthermore, TAX1BP1 preferentially binds phospho-A20, which explains the enhanced interaction between TAX1BP1L207I and A20S254R. A20 phosphorylation regulates its abundance, not by MALT1-mediated degradation, but probably via autophagy. Thus, while A20 phosphorylation has been implicated in A20 protease activity, an epistatic interaction between rare human genetic variants reveals how phosphorylation also regulates A20 abundance.

Tissue-specific peripheral tolerance mechanisms are essential to prevent autoimmunity. The cornea is immune privileged, and anterior chamber-associated immune deviation (ACAID) governs its inner surface. However, the mechanisms that apply to corneal epithelial (outer surface) antigens remain unknown. Using an inducible, cornea-restricted neoantigen mouse model, we found that the cornea relies on inducible regulatory T cells (Tregs) rather than ignorance or ACAID for its epithelial antigens. Although the cornea is both avascular and alymphatic, its epithelial antigens are still efficiently presented by ocular surface-derived antigen-presenting cells to T cells in draining lymph nodes under homeostatic conditions, leading to conventional antigen-specific Treg expansion without ocular pathology. This tolerance was not absolute: systemic immunization redirected antigen-specific responses toward pathogenic effector T cells that disrupted epithelial barrier function. These findings identify Treg induction as a dominant mechanism of corneal epithelial immune homeostasis and demonstrate that inflammatory priming can render a tolerated corneal antigen into an autoimmune target, providing mechanistic insight into dry eye pathogenesis. SummaryThis study shows that immune tolerance to corneal epithelial neoantigens relies not on immune privilege but on peripherally induced regulatory T cells in the draining lymph nodes that can be subverted by innate activation, shedding light on ocular surface disease pathophysiology.

Why do some individuals develop mild COVID-19 while others progress to severe disease remains a central challenge in SARS-CoV-2 immunology. In this study, we leveraged the BACO Cohort - a unique historical cohort of immunologically naive, hospitalized COVID-19 patients from the first pandemic wave - to investigate early immune determinants of clinical disease trajectories. Integrating bulk RNA-seq, Olink proteomics, and systems serology, we identified two fundamentally distinct immune trajectories according to disease phenotypes. Severe patients exhibited upregulation of proinflammatory genes and monocyte-associated transcripts, alongside downregulation of genes related to T cell responses and immune signaling. Notably, an upregulation of inhibitory Fc-receptor-associated gene was also found in severe cases. In contrast, mild cases showed coordinated lymphoid activation and limited inflammation. Building on these findings, we performed a functional profiling of Fc-effector activity in the polyclonal serum of the patients and found that monocyte-mediated phagocytosis was a common feature of mild disease. Interestingly, this response was mainly driven by rapid induction of S1-specific antibodies. Conversely, severe patients tended to generate higher levels of S2-biased antibodies early after infection with poor Fc-effector functionality. Together, these findings demonstrate that early S1-directed, Fc-competent humoral immunity is a key determinant of favorable COVID-19 outcomes, while delayed functional maturation and early S2 bias characterized severe disease in the BACO cohort.

Ulcerative colitis (UC) is characterized by epithelial barrier dysfunction and dysregulated mucosal immune responses; however, the mechanisms driving disease onset remain poorly defined. Autoantibodies against the epithelial-restricted integrin v{beta}6 are a highly specific biomarker of UC that can precede clinical diagnosis by up to 10 years. Because v{beta}6 activates TGF{beta} at epithelial surfaces, we hypothesized that UC-associated v{beta}6 autoantibodies inhibit mucosal TGF{beta} activation and disrupt epithelial homeostasis. We showed that v{beta}6 autoantibodies were enriched in UC and that IgG from autoantibody-positive individuals inhibited v{beta}6-dependent activation of TGF{beta}. v{beta}6 blockade dampened TGF{beta} signaling and altered differentiation-associated gene programs in human intestinal epithelial cells. In mice, deletion of v caused expansion of inflammation-associated goblet cells in the colon and changes in intestinal immune cells. Using a novel mouse model, we showed that v{beta}6-specific autoantibody disrupted epithelial-immune crosstalk and increased susceptibility to DSS colitis. Together, these findings establish anti-v{beta}6 autoantibodies as active inhibitors of epithelial TGF{beta} signaling, constituting a de facto anti-cytokine response, rather than passive biomarkers. By linking preclinical seropositivity to impaired epithelial signaling and heightened susceptibility to colitis, this work identifies epithelial v{beta}6-dependent TGF{beta} activation as a pathway that may be leveraged to modify disease risk or limit disease severity. One Sentence SummaryUC-associated autoantibodies impair epithelial TGF{beta} activation, alter mucosal homeostasis, and predispose to colitis.

The transcription coregulator OCA-B promotes CD4+ T cell memory recall responses and autoimmunity. OCA-B T cell deletion prevents spontaneous type-1 diabetes (T1D) onset in non-obese diabetic (NOD) mice and blunts T1D in a subset of more aggressive models. However, the role of OCA-B in diabetes induced by treatment with immune checkpoint inhibitors (ICIs), and the role of OCA-B in the control of tumors with and without ICI treatment, has not been studied. Here we show that islet and pancreatic lymph node T cells from T1D individuals express measurable POU2AF1 mRNA. Deletion of OCA-B in T cells fully insulates 8-week-old non-obese diabetic (NOD) mice against ICI-induced diabetes and partially protects 12-week-old mice. Salivary and lacrimal gland infiltration and inflammation were also reduced. Protection was associated with a block in the differentiation of progenitor exhausted CD8+ T cells (TPEX) into terminally exhausted CD8+ T cells (TEX). We show that OCA-B T cell loss preserves anti-tumor immune responses following PD-1 blockade in different tumors and mouse strains. These findings point to a potential therapeutic window in which pharmaceuticals targeting OCA-B could be used to block the emergence of both spontaneous and ICI-induced autoimmunity while sparing anti-tumor immunity. We develop first-in-class small molecule inhibitors of Oct1/OCA-B transcription complexes and show that administration into NOD mice also blocks diabetes emergence following PD-1 blockade. These results identify OCA-B as a promising therapeutic target for the prevention of autoimmunity and immune-related adverse events (irAEs).

Recent evidence suggests that CD8+ T cells contribute to rheumatoid arthritis (RA) pathogenesis, however, their landscape of immune recognition, clonality, phenotypic and transcriptional characteristics, as well as functional properties remain poorly understood. Using in silico epitope prediction, barcoded pMHC multimer screening, single-cell transcriptomic and TCR repertoire analysis in blood and tissue of RA patients, we systematically interrogated CD8+ T-cell responses targeting RA-associated peptides. First, we identified HLA class I-restricted CD8+ T-cell responses against RA autoantigens. Second, we demonstrate that epitope-specific CD8+ T cells from RA patients display a distinct transcriptional footprint compared to healthy donors, which is characterized by features consistent with antigen experience, cytotoxicity and effector differentiation. In parallel, our data indicate that citrullination can modulate cross-recognition between peptide epitopes, suggesting that this post-translational modification may broaden or reshape antigen recognition within the CD8+ T-cell repertoire. Finally, we show that RA-associated TCR clonotypes are stable in peripheral blood over time, are comprised of phenotypically antigen-experienced cells, and can be detected in synovial tissue. Together, our study defines a set of HLA class I-restricted CD8+ T-cell epitopes associated with RA and provides mechanistic insight into how citrullinations may influence CD8+ T-cell recognition as well as interrogating the RA-associated CD8+ T cell clonotype landscape. These findings support a direct role for autoreactive CD8+ T cells in RA and provide a foundation for targeted immunotherapy.

Epstein-Barr virus (EBV) infection is nearly ubiquitous in humans and has been associated with multiple sclerosis (MS) and other immune-mediated diseases, yet mechanisms by which EBV-infected B-cells influence distal tissues remain incompletely understood. Extracellular vesicles (EVs) mediate intercellular communication during viral infection, but their integrated viral and host cargo has not been comprehensively defined in EBV-transformed B-cells generated from naturally infected individuals. Here, we performed an unbiased multiomic characterization of small EVs (sEVs) released from spontaneous lymphoblastoid cell lines (SLCLs) derived from normal donors and patients with stable or active MS, transformed ex vivo by endogenous wild-type EBV. Using surface profiling, quantitative proteomics, whole-genome sequencing of EV-associated DNA, total stranded RNA sequencing, droplet digital PCR, and super-resolution microscopy, we mapped the protein, DNA, and RNA cargo of these vesicles and determined their host and viral origins. SLCL sEVs contained canonical tetraspanins, B-cell markers, and were free of detectable virions. Proteomics identified over 6,000 shared proteins and revealed enrichment of nucleic acid-binding and chromatin-associated proteins. Whole-genome sequencing demonstrated abundant EV-associated DNA comprising two distinct compartments: high-molecular weight, DNase-sensitive DNA associated with the vesicle corona and DNase-resistant, nucleosome-sized ([~]130-150 bp) DNA protected within vesicles. In both compartments, DNA was overwhelmingly host-derived and broadly distributed across the genome, whereas EBV genomic DNA was minimal. RNA sequencing identified diverse EBV transcripts, with striking enrichment of the viral long noncoding RNA EBER1 across all lines. Super-resolution imaging and ddPCR confirmed EBER1 incorporation within individual vesicles. Notably, EBER1 has been detected in MS brain tissue in prior studies, and our findings provide a plausible vesicle-mediated mechanism for dissemination of this viral lncRNA from EBV-infected B-cells to distal sites. These findings establish a foundational multiomic profile of sEVs from wild-type EBV-transformed B-cells and reveal export of host DNA and EBER1, with broad implications for viral immunobiology and intercellular signaling in MS and beyond. SIGNIFICANCE STATEMENTEpstein-Barr virus (EBV) infects over 90% of adults worldwide and is strongly linked to multiple sclerosis (MS). How EBV-infected B-cells may communicate with distant tissues, including the central nervous system (CNS), remains unclear. We provide the first integrated multiomic profile of extracellular vesicles released from B-cells transformed by endogenous, wild-type EBV. These vesicles are enriched in nucleosome-associated host DNA and the viral long noncoding RNA EBER1 but contain minimal viral DNA. Because EBER1 has been detected in MS brain tissue, our findings suggest a vesicle-mediated mechanism by which EBV-infected B-cells could deliver viral RNA to the CNS independently of infectious virus. These results establish a framework for understanding how EBV latency reshapes intercellular communication in immune-mediated disease.

The gastrointestinal tract (GI) is the largest environmental mucosal interface and is exposed to diverse commensal and pathogenic microbes. B cells are a prevalent immune component of the GI tract and its associated secondary lymphoid organs, yet we know little about the diversity and stability of distinct transcriptional programs that modulate B cell responses against different classes of pathogens or environmental perturbations. A subset of B cells defined by expression of the transcription factor T-bet, has been canonically associated with antiviral immunity through IgG production. However, the role of T-bet expressing B cells in mucosal tissues, where IgA responses predominate, is poorly understood. Here, we identify a population of intestinal T-bet+ B cells that, in the absence of overt perturbation, constitutes a minor fraction of intestinal associated B cells and undergoes continuous turnover. In contrast, during enteric viral infection with murine norovirus (MNV), T-bet B cells undergo a marked expansion, with T-bet expression stably maintained in the majority of virus-specific B cells, including IgG2c and IgA switched B cells. Moreover, virus-reactive IgG2c and IgA B cells arise independently rather than through sequential switching, and B cell intrinsic T-bet expression is required for effective germinal center responses but dispensable for IgA class switching. Moreover, T-bet expressing B cells are required for the generation of all MNV-specific circulating IgG and mucosal IgA, and for protection upon re-encounter with the virus. Together, these findings establish T-bet expressing B cells as a specialized B cell subset essential for mucosal immunity and protection against norovirus infection.

Therapeutic blockade of IL-17 and TNF can effectively treat inflammatory skin diseases such as hidradenitis suppurativa and psoriasis, yet the relative importance of the different cell types that respond to IL-17 and TNF remains unresolved. Keratinocytes are viewed as the dominant effector cells, whereas fibroblasts have recently emerged as important contributors. In mice, topical imiquimod induces IL-17- and TNF-dependent skin inflammation and is frequently used to model psoriasis. Here, we demonstrate that intradermal injection of recombinant IL-17 and TNF elicits skin inflammation with features of hidradenitis suppurativa, including a gene expression program that is distinct from psoriasis and imiquimod-induced inflammation. Single-cell transcriptomic network analysis identified dermal fibroblasts as the dominant cell communication hub in hidradenitis suppurativa and in mice injected with IL-17 and TNF. In contrast, fibroblasts and keratinocytes both show strong network involvement in psoriasis and in mice challenged with imiquimod. Cell-type-specific deletion of IL-17 receptor A in mice revealed that imiquimod-induced inflammation depends equally on IL-17 signaling in fibroblasts and keratinocytes, whereas inflammation induced by intradermal IL-17 and TNF only requires fibroblasts to recognize IL-17 and is independent of keratinocyte IL-17 sensing. Single-cell transcriptomic analysis of these conditional knockout mice further demonstrated that keratinocytes and fibroblasts activate divergent and disease-dependent transcriptional programs following activation by IL-17. Together, these findings introduce a new conceptual framework wherein IL-17 signaling is routed through distinct cellular and molecular pathways depending on disease context and establish complementary experimental systems for interrogating type 17 skin inflammation.

Chimeric antigen receptor (CAR)-T cell therapies can induce drug-free remission in systemic lupus erythematosus (SLE), but indiscriminate B cell targeting causes immunosuppression, unnecessary infections, and cytokine toxicities that preclude widespread use. Here, we overcome this by targeting the 9G4 idiotope, a shared structural feature of pathogenic B cell receptors encoded by the IGHV4-34 gene. We engineered anti-9G4 CAR-T cells and chimeric TCR-T cells to selectively eliminate autoreactive B cells while preserving protective immunity. Both platforms eradicated autoreactive B cells and autoantibodies in vitro and in vivo, spared normal B cells, and markedly reduced cytokine release compared to conventional CAR-T cells. This precision extended to cold agglutinin disease and lymphoma. These findings establish a framework for IGHV idiotope-directed cellular therapies for treating autoimmune and neoplastic diseases while preserving immune competence.

Effective T cell reconstitution in people living with HIV is central to durable immune control and cure strategies. Sustained thymic output underpins T cell recovery and requires continuous seeding by T cell-committed progenitors originating in the bone marrow (BM). Using the SIV/rhesus macaque model, we identified a thymus-seeding progenitor (TSP; CD4-CD8-CD34CD38-CD7) in BM declining rapidly following SIV infection. This loss closely associated with reduction in T cell lineage committed differentiation of BM-derived hematopoietic stem and progenitor cells (HSPCs). Importantly, both the decline in TSPs and the impairment of pre-thymic T cell potential were strongly associated with early loss of viral control, independent of peripheral T cell dynamics. Plasma interleukin-6 (IL-6) levels robustly predicted the magnitude of TSP loss and the restriction of T cell-biased HSPC differentiation. Integrated transcriptomic and proteomic analyses revealed inflammatory imprinting of HSPCs characterized by activation of the IL-6-JAK-STAT axis, inflammasome engagement, and coordinated suppression of key T cell specification factors, including RUNX1, FYN, and ZAP70. In a nonanimal model of thymopoiesis, IL-6 exposure of rhesus macaque and human HSPCs inhibited their transition from DN1 (CD38-) to DN2 (CD38) TSP states, indicating an early block in T cell lineage commitment. Conversely, ex vivo IL-6 receptor blockade restored thymocyte differentiation to levels comparable to untreated controls. Collectively, these findings demonstrate that pathogenic inflammation restricts pre-thymic T cell development early after infection, directly contributing to loss of viral control. These findings have important implications for understanding the mediators of anti-viral T cell immunity and HIV cure.

Innate and adaptive immune responses play critical roles in the pathogenesis of inflammatory bowel disease (IBD), yet the molecular pathways integrating these responses remain elusive. Here, we identify DNAM-1 immunoreceptor as a central driver of colitis through distinct, cell type-specific mechanisms. Transcriptomic analyses of human and murine group 3 innate lymphoid cells (ILC3s) revealed DNAM-1 as a conserved IL-23-responsive surface molecule associated with inflammatory cytokine production. In an innate immune-driven anti-CD40 monoclonal antibody (mAb)-induced colitis model, DNAM-1 expressed on ILC3s promoted intestinal inflammation by enhancing IL-22 and GM-CSF production via the integration of the Akt-mTORC1-HIF-1 signaling pathway. Genetic ablation or antibody-mediated blockade of DNAM-1 attenuated inflammatory cytokine production and disease severity. Paradoxically, in T cell-dependent colitis, DNAM-1 expression on dendritic cells, but not on ILC3s or CD4 T cells, exacerbated disease by promoting dendritic cell activation and pathogenic Th1 and Th17 differentiation. Notably, therapeutic blockade of DNAM-1 ameliorated disease in both colitis models and exerted complementary effects when combined with anti-TNF therapy, accompanied by modulation of immune activation programs distinct from those regulated by TNF inhibition. Collectively, these findings establish DNAM-1 as a pivotal regulator of intestinal inflammation bridging innate and adaptive immunity and identify DNAM-1 blockade as a next-generation therapeutic strategy for IBD. Highlight{blacktriangleright} DNAM-1 is an IL-23-responsive receptor conserved in human and mouse ILC3s. {blacktriangleright}DNAM-1 on ILC3s drives innate colitis via Akt-mTORC1-HIF-1 signaling. {blacktriangleright}DNAM-1 on DCs promotes T cell-dependent colitis by inducing Th1/Th17 cells. {blacktriangleright}DNAM-1 blockade targets immune pathways distinct from TNF inhibition. {blacktriangleright}Combined DNAM-1 and TNF blockade shows additive therapeutic efficacy in colitis.