Science Immunology

Conventional dendritic cells navigate complex tissues and sample peripheral antigens, balancing immune suppression and activation to achieve tissue homeostasis. However, it remains unclear how an individual dendritic cells reconciles co-incident signals from immunological opposing antigens within the tissue or tumor microenvironment, where tolerogenic self-antigen and immunogenic tumor antigen or microbes coexist. Here, using complementary in vivo fluorescent reporter systems, high-resolution imaging and endosomal profiling, we simultaneously tracked uptake, intracellular processing and cross-presentation of cutaneous self, tumor and microbial antigens in murine skin tissue, tumors and draining lymph nodes. We find that a substantial fraction of dendritic cells acquire antigen from multiple sources and that localization within endosomal compartments is dictated by antigen source. Notably, type 1 conventional dendritic cells that co-process self and tumor antigen represent a significant proportion of tumor antigen-bearing dendritic cells in the tumor and tumor draining lymph node. These dual-antigen loaded dendritic cells display a diminished capacity to prime tumor-specific CD8+ T cells and a marked reduction in tumor derived peptide presented on surface MHCI, while cross-priming of self-antigen specific T cells is significantly increased. These changes occur despite equivalent or greater tumor antigen uptake relative to self-antigen and high expression of surface MHCI and costimulatory molecules. Together, these data support a model in which multiantigen processing within dendritic cells can bias peptide loading away from tumor-derived epitopes, thereby limiting tumor-specific cross-priming. Modulating the antigenic context of the tumor microenvironment or endosomal routing after antigen uptake may therefore represent a strategy to restore effective dendritic cell-mediated antitumor immunity.

Tissue-resident memory B cells (BRM) provide powerful localized protection against microbial infection in barrier tissues. It is unknown if analogous BRM populations survey solid tumors and contribute to anti-cancer immunity. We profiled B cells from patients with colorectal cancer and cutaneous basal cell carcinoma and identified a CD69+ memory B cell population consistent with a tissue-resident phenotype. Integrative analysis of transcriptomic datasets identified an optimized signature enriched across cancer types. Tumor infiltrating BRM-like cells preferentially exhibited autoreactivity and their signature correlated with patient outcomes and response to immunotherapy. Skin and lung targeted vaccination established localized BRM that provided IgA dependent organ specific protection upon tumor challenge in murine models. These findings establish BRM as an active component of anti-cancer immunity via preferential reactivity to tumor associated self-antigens.

Mucosal-associated invariant T (MAIT) cells are enriched at barrier sites, but their role in autoimmune skin inflammation remains unknown. Using cutaneous lupus as a model, we identify MAIT cells as protective regulators of skin inflammation and as critical upstream modulators of regulatory T cells (Treg). Topical MAIT cell activation with 5-OP-RU induced durable resolution of spontaneous skin lesions in MRL/lpr mice and suppressed TLR7-driven skin inflammation. MAIT cell activation selectively expanded and activated Treg populations in both healthy and lupus-like skin, while suppressing effector T cell cytokine production and cytotoxic programs. This MAIT-Treg axis was also activated in UV light-driven barrier injury in healthy murine and human skin, where MAIT cells were required for UV-elicited Treg expansion and function. In lupus-like skin, local MAIT cell activation restored the defective UVB-induced Treg response and limited CD8+ T cell expansion. Mechanistically, CCR2+ monocyte-derived antigen-presenting cells and IL-15 signaling were required for MAIT cell-driven Treg accumulation and therapeutic benefits of MAIT cells in inflamed skin. These studies identify a MAIT-IL-15-Treg axis that links barrier injury sensing to immune regulation, which is disrupted in cutaneous lupus, and nominate therapeutic MAIT cell activation as an unappreciated strategy for restoring immune homeostasis in inflamed skin.

HLA-C-restricted CD8+ T-cell responses remain poorly defined compared with HLA-A and HLA-B responses, despite the central role of HLA-C as both a peptide-presenting molecule and a ligand for killer-cell immunoglobulin-like receptors (KIRs). This dual function creates a major challenge for pHLA multimer-based antigen-specific T-cell analysis, as HLA-C multimers may bind CD8+ T-cells through either antigen-specific TCRs or KIRs. Here, we show that KIR expression on CD8+ T-cells drives TCR-independent binding to pHLA-C multimers, leading to overestimation of HLA-C-restricted antigen-specific T-cell responses. Using HLA-mismatched donor settings and cancer neoantigen pHLA-C multimers, we demonstrate that apparent multimer-positive CD8+ T-cells can arise from KIR-mediated recognition rather than cognate TCR specificity. We further show that KIR blockade before pHLA-C multimer staining removes non-TCR-specific binding, and applying this strategy to large-scale analysis of CMV, EBV, and SARS-CoV-2 antigens, we identify TCR-specific HLA-C-restricted CD8+ T-cell populations. Importantly, KIR-mediated pHLA-C binding is peptide-selective rather than uniform across all peptide-HLA-C complexes. Single-cell transcriptomic, phenotypic, and clonotypic analyses further demonstrate that KIR-mediated and TCR-mediated pHLA-C multimer binding define transcriptionally and clonally distinct CD8+ T-cell populations. Together, these findings establish KIR-mediated pHLA-C recognition as a major confounder in HLA-C multimer-based T-cell analysis. By separating KIR- from TCR-mediated binding, our approach provides a practical framework for accurate discovery and characterization of HLA-C-restricted antigen-specific CD8+ T-cells across viral infection and cancer.

How the immune system surveys nascent tumors and how this surveillance is subverted remain poorly understood. Using high-plex cyclic immunofluorescence and 3D imaging, we identified regulatory T (Treg) cells that co-localize with tissue-resident memory (TRM)-like T cells in early-stage human melanoma. In an autochthonous Braf/PTEN melanoma model expressing a defined tumor antigen, the initial CD8+ T cell infiltrate adopts a CD103+CD101+ TRM-like fate, establishing active immunosurveillance within nascent lesions. TRM-like cells dominate early tumors, occupy a stable epidermal niche, express effector molecules, and initiate T cell recruitment. However, Treg cells adopt a parallel tissue-resident phenotype, co-localizing with TRM-like cells and restraining both cytotoxic and sentinel functions. Tumor-site-specific Treg depletion reactivated TRM-like cells, drove robust T cell recruitment, expanded tumor-specific responses, and limited tumor growth. These findings reveal how early immunosurveillance is established through tissue-resident programs and identify Treg co-option of this response as a critical mechanism of tumor immune evasion. One Sentence SummaryNascent melanoma imprints a tissue-resident program on the initial CD8+ T cell infiltrate, which is suppressed by regulatory T cells as a critical checkpoint in immune evasion.

Antigen-presenting cell (APC) interactions with cytotoxic T cells are critical for anti-tumour immunity and response to immune checkpoint blockade (ICB), yet context-specific regulators in the tumour microenvironment remain not fully defined. Here we identify the lectin receptor SIGLEC1 as a key mediator of macrophage-T cell interactions in human melanoma. In a well-characterized patient cohort, SIGLEC1 was selectively upregulated in inflammatory macrophages physically associated with activated/exhausted CD8 T cells. Imaging and functional analyses revealed that SIGLEC1 accumulates at the macrophage-T cell interface and promotes cell clustering. SIGLEC1 ligands were enriched on activated T cells, and their blockade reduced cytotoxic cytokine production ex vivo. Single-cell (spatial) transcriptomics across independent ICB-treated melanoma cohorts showed that SIGLEC1 macrophages localize near CD8 T cells and are enriched in responders, where they also associate with T cells expressing activation/exhaustion markers. These findings define a SIGLEC1-dependent macrophage-T cell niche linked to effective immunotherapy.

Lung repair in response to viral infection requires integrated communication between epithelial and immune compartments, yet the impact of antiviral mediators on epithelial regenerative capacity remains poorly defined. Here, we demonstrate that type I interferon (IFN-I) signaling primes the lung for alveolar renewal following viral challenge. IFN-I contributes to the induction of an interferon-stimulated gene-high (ISG)hi Sca-1Pos population of alveolar type II (ATII) epithelial cells. Sca-1Pos ATIIs exhibit enhanced proliferative capacity and increased organoid-forming efficiency compared with their Sca-1Neg counterparts. Viral challenge concurrently drives phenotypic reprogramming of tissueresident alveolar macrophages (trAMs). Sca-1Pos ATIIs display heightened responsiveness to oncostatin M (OSM) and, following viral challenge, require trAM-derived OSM for their proliferation. Together, these findings reveal that viral stimuli induce coordinated IFN-I-dependent epithelial and macrophage states that poise the lung for regeneration, positioning IFN-I not only as a central antiviral defense mechanism but as a priming signal that prepares lung tissue for renewal.

Food allergies are associated with progressive gastrointestinal symptoms driven by exacerbated mucosal type-2 immunity. Here, we investigated whether cellular interactions between the gut epithelium and innate immune cells regulate the severity of allergic symptoms in mice. Using the BALB/c OVA-alum food allergy model, we observed that repeated oral allergen challenges remodel the gut epithelium, expanding tuft cells, while shifting the intestinal stem cell niche toward a fetal-like repair state. Using uLIPSTIC, we systematically characterized in vivo immune-epithelial interactions and found that eosinophils and mast cells directly interact with intestinal epithelial cells (iECs) in an allergen challenge-dependent manner. Epithelial subset-specific uLIPSTIC provided further resolution and revealed that eosinophils and mast cells contact enteroendocrine cells and Paneth cells in a regionally compartmentalized manner. Allergic challenge was associated with rapid eosinophil migration towards the crypts and modulation of iEC differentiation. Depletion of eosinophils using two independent approaches reversed key markers of food allergy-associated epithelial remodeling, while exacerbating allergic diarrhea and mortality from anaphylactic shock. These findings establish eosinophils as orchestrators of protective epithelial remodeling in food allergies.

Infection-and vaccination-induced memory CD8+ T cells provide protection upon subsequent exposure to cognate antigen through their increased abundance and robust per-cell responses. However, how prior antigen experience alters T-cell activation programs remains poorly understood. We longitudinally profiled gene expression in naive, central memory, and effector memory CD8+ T cells in response to cognate antigen across multiple models of acute infection. Naive T cells engaged TOX-and TCF7-centered programs and generated early stem-like central memory precursors. Their initially slow proliferation was followed by rapid expansion and the production of large numbers of short-lived effector cells. Central memory T cells rapidly triggered effector and proliferation programs while maintaining a smaller self-renewing population. Effector memory T cells expanded poorly and generated almost exclusively effector progeny. Effector progeny derived from both memory subsets survived contraction more efficiently than naive T-cell-derived progeny and established persistent effector memory populations. These data show that prior antigen experience does not simply accelerate CD8+ T-cell activation but redirects cell-intrinsic programs that shape progeny fate and persistence. These distinct programs may reflect adaptation to primary versus repeated antigen exposure and suggest that infection and vaccination history can shape the balance between stem-like memory and persistent effector populations.

Fibrosing skin diseases are highly morbid conditions with diverse clinical and histopathologic features. Prior work, primarily in systemic sclerosis (SSc), has yielded mixed data regarding the immune drivers of fibrosis, as well as the identity and spatial localization of pro-fibrotic fibroblast cell subsets. Here, we focus on morphea and eosinophilic fasciitis (EF), which cause more acutely inflammatory skin fibrosis. Using multimodal single-nucleus and spatial transcriptomics, we find that effector CD8+ T cells are highly enriched in fibrotic skin. These cells are particularly abundant in inflammatory tissue domains bordering fibrotic stroma, which are marked by expression of interferon-{gamma} stimulated genes. Inflammatory domains feature a loss of local homeostatic fibroblast populations and replacement with ADAM12-expressing inflammatory fibroblasts and myofibroblasts, which co-localize closely with CD8+ T cells. All subtypes of morphea featured similar patterns of CD8+ T-cell-associated fibro-inflammatory zonation and fibroblast transformation, suggesting that shared mechanisms can drive fibrosis across stromal compartments of skin. We apply these findings to a large publicly available scleroderma dataset and find that similar processes occur in SSc. Mechanistically, ablation of CD8+ T cells in mice ameliorates bleomycin-driven inflammation and fibrosis, as does fibroblast-intrinsic abrogation of IFN-{gamma} signaling. These data establish CD8+ T cell-driven fibrogenesis as a key feature of fibrosing skin diseases and raise the prospect of targeting CD8+ T cells in autoimmune fibrosis more broadly. One sentence summarySpatial profiling of morphea-spectrum diseases reveals CD8 T cells as key drivers of fibrosis through fibroblast IFN-{gamma} signaling.

Staphylococcus aureus remains a major global pathogen with no licensed vaccine and high recurrent infection burden, yet correlates of protection remain undefined. In a prospective pediatric cohort, we profiled 319 children spanning non-carriers, asymptomatic carriers, those with skin and soft tissue infection (SSTI), or invasive disease. We interrogated 182,149 antibody features, generating the most comprehensive S. aureus immune profiling dataset to date. Antibody responses increased with age, marked by expansion of IgG subclasses and Fc-receptor engagement. Asymptomatic carriage was associated with functional antibody profiles targeting conserved surface antigens and select toxins. Multivariate modeling robustly distinguished clinical phenotypes and identified high-value antigens associated with disease resilience. Protection from recurrent disease converged on enhanced Fc{gamma}R binding and antibody effector function. These findings nominate key antigen targets, and highlight anti-Hla neutralizing antibodies and functional antibodies to additional surface antigens that can be recapitulated through Fc engineering, informing next-generation vaccine and monoclonal antibody strategies.

Upon skin colonization, the prevalent human skin commensal S. epidermidis can elicit a CD8+ T cell response that protects against pathogens or clears tumors. The microbial features that drive this response are undefined, limiting our ability to understand and predict commensal-immune crosstalk and to engineer potent commensal-derived immunotherapies. To uncover these microbial features, we harnessed both the natural variation in CD8+ T cell induction across primary human isolates of Staphylococcus and our ability to genetically manipulate these strains. Stimulatory strains exhibit increased quorum sensing activation, which turns on a unique commensal-associated gene family, called phenol-soluble modulin {varepsilon} (PSM{varepsilon}), that is required for CD8+ T cell activation. PSM{varepsilon} not only acts as the immunodominant CD8+ T cell antigen but also enhances cross-presentation in an antigen-agnostic manner. Co-delivering PSM{varepsilon} promotes CD8+ T cell priming to an exogenous antigen via a mechanism that is independent of formyl peptide receptor and co-stimulatory receptor upregulation. Thus, we demonstrate that specific aspects of microbiome-immune crosstalk can be distilled to molecular components, which engage in previously undescribed mechanisms and can be harnessed for immunotherapy without requiring live bacterial colonization.

Dimeric immunoglobulin A (dIgA) is generated from IgA monomers (mIgA) via JCHAIN-dependent polymerization. DIgA is transported across epithelial barriers by the poly Ig receptor (PIGR) and confers mucosal protection, while serum contains substantial amounts of IgA monomers. Distinct plasma cell subsets have been proposed to produce either monomeric or dimeric IgA, with bone marrow plasma cells as a primary source of mIgA. Here, we addressed whether IgA plasma cell populations segregate based on mIgA or dIgA production. Flow cytometric analysis of antibody-secreting cells from bone marrow, lymphoid and mucosal tissues revealed universal intracellular JCHAIN expression across isotypes and failed to identify a discrete JCHAIN-negative IgA plasma cell population. To detect polymeric IgA, we generated a recombinant soluble PIGR that selectively bound JCHAIN-containing dIgA in Western blot, ELISA, and flow cytometry. Soluble PIGR binding was detected in all IgA plasma cells irrespective of tissue origin, arguing against a dedicated mIgA-producing plasma cell subset incapable of dIgA formation. Ex vivo cultures and single-cell DropMap secretion assays demonstrated that bone marrow and lamina propria IgA antibody-secreting cells co-secrete mIgA and dIgA. These findings suggest that dIgA assembly and secretion are general properties of IgA plasma cells and disfavor a dedicated mIgA-producing population.

CD4+ T cells coordinate immune responses to infections and cancers and initiate many autoimmune diseases, yet the intracellular pathways that generate the peptide antigens they recognize remain incompletely understood. Progress has been limited in part by the scarcity of reagents that directly detect defined peptide:MHC class II (pMHC-II) complexes. Here, we established an mRNA vaccine-based pipeline to generate and characterize T cell receptor (TCR)-like antibodies. One result was 1D6, a monoclonal antibody specific for NA25:Ab, an influenza A/PR8 neuraminidase-derived epitope presented by MHC-II. 1D6 bound NA25:Ab with high affinity and specificity. 1D6 recognizes NA25:Ab through binding determinants partially distinct from those used by the cognate TCR. Using this reagent, we confirmed the proteasome dependence of NA25 presentation and showed that NA25:Ab accumulates in intracellular MHC-II loading compartments without a major requirement for canonical macroautophagy, pointing to an unconventional mode of antigen presentation. These findings establish TCR-like antibodies as powerful tools for dissecting noncanonical MHC-II antigen processing pathways.

{gamma}{delta} T cells are promising mediators of cancer immunotherapy, yet their potential to drive autoimmunity remains incompletely understood. Here, we identify a feedback mechanism in which innate-like V{gamma}1.1V{delta}6.3 T cells are reprogrammed into ILC1-like cells, thereby restraining autoimmune pathology. We define a previously unrecognized ILC1 subset whose development depends on an intact Tcrd locus. These cells predominantly harbor productive V{gamma}1.1 and V{delta}6 rearrangements, consistent with their origin from V{gamma}1.1V{delta}6.3 T cells. Mechanistically, TCR signaling induces Id3, which suppresses E protein-dependent activation of T cell-specific genes, including that encoding V{delta}6.3. Id3 ablation drives robust expansion of V{gamma}1.1V{delta}6.3 T cells and severe autoimmunity, characterized by tissue infiltration, autoantibody production, enhanced T follicular helper cell differentiation, and accumulation of germinal center and age-associated B cells. Together with previously described exocrine dysfunction, these features resemble human Sjogrens disease. Consistent with this, we observed in the salivary glands of Sjogrens disease patients an increased frequency of CD4-CD8- T cells enriched for {gamma}{delta} T cells, including subsets functionally analogous to murine V{gamma}1.1V{delta}6.3 cells. Collectively, these findings uncover a TCR-Id3-dependent reprogramming pathway that limit the pathogenic potential of harmful {gamma}{delta} T cells.

The mechanism by which T cell receptors (TCR) recognise mycobacterial lipids presented by CD1 family members not well understood. We used CD1c tetramers loaded with the mycobacterial phosphomycoketide (PM) or mannosyl-PM (MPM) to isolate T cells ex vivo in healthy blood donors and in individuals from a tuberculosis (TB)-endemic region of South Africa, with higher frequencies observed in individuals from the TB-endemic region. High throughput analysis of >200 paired CD1c-mycoketide tetramer+ {beta}TCRs identified a conserved TCR motif, encoded by TRBV4-1 or TRBV7-9 variable region genes in greater than half of TCRs sequenced. A cryo-EM structure of a TRBV7-9+ TCR in complex with CD1c-PM demonstrated that the TCR bound to the F side of CD1c, directly contacting the phospholipid antigen and F-portal residues. Analysis of multiple T cell clones interacting with CD1c mutants suggested that this TCR docking mode is representative of the larger TRBV7-9+ T cell population. Collectively, this study provides insight into mycobacterial lipid-antigen recognition by CD1c-restricted T cells. SummaryCao and Soliman et al study CD1c-restricted human T cells that recognize mycobacterial phosphomycoketide lipids, where they are shown to be more frequent in blood a TB-endemic region. The authors describe a strong TCR-{beta} repertoire bias and use cryoEM to provide a high-resolution structure of an archetypal TCR engaging CD1c in complex with a mycobacterial lipid.

The impaired clearance of apoptotic cells has long been associated with systemic autoimmune diseases like Sjogrens disease (SjD), which is characterised by autoantibodies targeting antigens on apoptotic cells. However, most studies analysing human samples have used patient-derived phagocytes and in vitro generated apoptotic cells, which do not reflect the heterogeneity of patient-derived apoptotic bodies (ApoBDs). Here, we molecularly and functionally compare ApoBDs derived from patients with SjD and healthy donors. ApoBDs were increased in the circulation in SjD and induced atypical memory B cell expansion, which was attenuated by blocking B cell receptor (BCR) and Toll-like receptors (TLR) 7-9 signalling. Co-cultures of ApoBDs and B cells drove autoantibody production. Macrophages engulfing SjD ApoBDs had a distinct inflammatory profile compared to macrophages engulfing healthy control ApoBDs. These findings define patient-derived ApoBDs as immunostimulatory substrates capable of driving innate and adaptive immune responses consistent with the pathogenic features observed in SjD, hence opening a new avenue of diagnostic and therapeutic development.

Colorectal cancer (CRC) remains a leading cause of cancer mortality, with most cases refractory to immunotherapy. Distinguishing tumor-induced from steady-state mucosal T cell responses has been a critical barrier to understanding antitumor immunity in CRC. Using orthotopic transplantation of CRC organoids with and without metastatic potential, combined with temporal T cell fate-mapping, we show that non-metastatic tumors elicit early recruitment of CD8{beta}+ and CD4+ T cells that acquired cytotoxic and Th1-like programs, whereas pro-metastatic tumors induce a naive-like, hypoactivated state. Tumor-infiltrating CD4+ T cells underwent clonal expansion, including clones recognizing microbial and dietary antigens. T cells in physical contact with tumor cells, identified by uLIPSTIC, were enriched for expanded and cytotoxic clones. Fate-mapped T cells from non-metastatic tumors suppressed tumor growth in an IFN-{gamma}-dependent manner, whereas pro-metastatic tumor-derived T cells failed to do so. Mechanistically, pro-metastatic tumors downregulated MHCII, and Ciita targeting in non-metastatic organoids reduced CD4+ clonal expansion and led to tumor progression. Together, these findings define divergent early T cell trajectories associated with CRC metastatic potential, indicating that ineffective local immune engagement precedes metastatic dissemination.

Epithelial remodeling is a hallmark of host antiviral responses that strengthen barrier defenses against infection. Our current understanding of viral pathophysiology within the nasal epithelium, the initial site of most respiratory viral infections, remains incomplete due to limited understanding of the native tissue architecture and protective epithelial remodeling during immune events. Leveraging coronavirus disease 2019 (COVID-19) as a model, we applied spatial multi-omics on nasal cross-sectional tissues to characterize the immune-epithelial landscape during infection, identifying a coordinated increase in goblet cells and suppressive macrophages associated with elevated IL13 in the immune compartment. Our results further reveal that goblet cell and suppressive macrophage enrichment are spatially linked in proximity to IL13-expressing CD4 T cells, consistent with IL13-driven remodeling in situ. Using a primary human nasal air-liquid interface model, we demonstrate that IL13 alone is sufficient to remodel epithelial composition and morphology, subsequently restricting viral infection by reshaping the apical mucus barrier of the nasal epithelium. Our findings uncover a spatially organized, IL13-driven circuit for immune-epithelial remodeling as a protective barrier against respiratory viral infections.

Proteinase 3 (PR3) anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is associated with HLA-DR15, implicating HLA-DR15-restricted CD4 T cell autoimmunity in the disease. However, the PR3 epitopes presented by HLA-DR15 and the autoreactive CD4 T cell responses they elicit are undefined. Using humanized hPR3.DR15+ mice, we identified PR3216-231 as an immunodominant human PR3-derived CD4 T cell epitope presented by HLA-DR15. Immunopeptidomic profiling confirmed the natural processing and HLA-DR15-restricted presentation of PR3216-231. Structural analyses of HLA-DR15-PR3216-231 complexes revealed an unconventional mode of HLA class II antigen presentation, in which a 10 amino acid peptide core occupies the 9 amino acid binding groove, causing a central kink in the bound peptide. PR3216-231-specific CD4 T cells from both hPR3.DR15+ mice and patients with PR3-ANCA-associated vasculitis exhibited convergent T cell receptor features, and patients with active vasculitis displayed a clonally expanded, PR3216-231-specific CD4 TCR repertoire. Immunization of hPR3.DR15 mice with PR3216-231 induced cell-mediated glomerulonephritis characterized by increased renal infiltration of CD4 T cells and macrophages together with segmental glomerular necrosis. These findings identify a nephritogenic PR3-derived CD4 T cell epitope presented by HLA-DR15 in ANCA-associated vasculitis and define a new extended core binding pattern, broadening our understanding of HLA class II peptide presentation.