Nature Immunology

Single-cell studies have defined immune states in inflammatory bowel disease (IBD), but how adaptive receptor histories organize circulating immunity remains unclear. We generated a single-cell transcriptomic atlas of peripheral blood from 249 participants with Crohn's disease, ulcerative colitis, or non-IBD control status, including 182 with productive TCR and BCR recovery. Expanded TCR clonotypes marked inflammatory-memory and cytotoxic states, while distinct but similar paired TCRs shared inflammatory programs across participants. BCR lineage maturation linked IgA-associated mucosal and plasma B cell programs to somatic mutation and class switching, distinguishing maturation-associated biology from clonal expansion. Helper, regulatory, and cytotoxic T-cell programs covaried with B-cell states, and inferred interactions nominated reciprocal antigen-presentation and helper pathways. Repertoire-based machine learning distinguished diagnosis, inflammation, and contemporaneous six-month treatment-response status. Together, this atlas connects receptor architecture to coordinated systemic immune remodeling, establishes a foundation for repertoire-informed patient stratification, and prioritizes candidate mechanisms of IBD pathogenesis.

T and B cell-mediated immunosurveillance of the central nervous system (CNS) can become maladaptive in multiple sclerosis (MS). Epstein-Barr virus (EBV) is a likely driver of MS, yet how exactly EBV-specific T cells contribute remains unclear. We generated an antigen-resolved atlas of blood and cerebrospinal fluid (CSF) T cells from untreated MS patients and controls. T cell clones carrying a GZMK effector-memory program in blood were CSF-biased, particularly in MS, and associated with EBV reactivity. In CSF, EBV-reactive GZMK CD8 T cells engaged B lineage cells. Activated CD8 T cells promoted atypical B cell and plasmablast formation, whereas GZMK-enriched effector-memory cells induced IL-6 and IL-8 release from myeloid cells. Together, these findings identify an infection-imprinted, CNS-biased state and support a model in which EBV-specific CD8 T cells contribute to inflammation through a non-canonical mode of B cell and myeloid cell activation.

Inflammatory signals are broadly conserved, yet how tissue context converts them into programs of recovery or maladaptive repair remains unclear. Using kidney injury as a model of inflammation-to-repair transitions, we identify an injury-induced proximal-tubule complement program in which cell-intrinsic complement proteins are repurposed across subcellular compartments to couple inflammation to metabolic and chromatin regulation and promote maladaptive fibrotic remodeling. Mechanistically, myeloid-derived IL-1b; signals through IL-1R1 on injured tubular cells to recruit NF-kB and AP-1 to C3 and Cfb, coordinately inducing complement component 3 (C3) and Factor B (FB). Cytoplasmic FB drives cleavage-activation of cell-intrinsic C3, which supports tubular cell mitochondrial metabolic adaptation to stress and accumulation of C3aR-expressing macrophages around injured tubules. Nuclear FB, on the other hand, binds chromatin through a previously unrecognized DNA-binding interface and mediates histone H3 proteolysis and the preferential remodeling of chromatin promotors enriched in transcriptional programs relevant to maladaptive repair. Key features of this injury-associated C3-FB response, including intranuclear FB, are conserved in human kidney disease, associate with kidney dysfunction, and distinguish diseased from healthy kidneys. Together, these findings suggest that extracellular complement-targeting therapies may miss disease-relevant intracellular functions and suggest nuclear FB as a distinct target whose chromatin interaction and processing capacity could selectively limit maladaptive tissue responses beyond conventional inhibition.

Chronic or persistent T cell activation is widely thought to culminate in T cell exhaustion, yet how autoreactive CD8+ T cells remain functionally intact despite sustained self-antigen exposure is poorly understood. In chronic infection and cancer this durability is attributed to stem-like, TCF1+ PD-1+ progenitor-exhausted (Tpex) cells that reside in lymphoid tissue and continuously replenish functional effectors; whether such a reservoir operates within a chronically inflamed peripheral organ during sterile autoimmunity is unknown. Here we show that mice lacking the lysosomal nuclease DNase2a together with the type I interferon receptor Ifnar1 (Dnase2a-/- Ifnar1-/-) develop spontaneous, progressive hepatic inflammation. This hepatitis was dependent on the endosomal DNA sensor TLR9, identifying self-DNA as the initiating ligand. Inflammation was marked by expansion of inflammatory macrophages and accumulation of CD8+ T cells co-expressing PD-1 and TOX that retained, rather than lost, effector function. Paired single-cell TCR and transcriptomic analysis revealed progenitor-exhausted T cells within the liver itself that shared clonotypes with clonally expanded PD-1+ TOX+ T cells, defining a locally operating progenitor-to-effector pipeline. Spatial transcriptomics positioned these intrahepatic T cell clusters adjacent to IL-27-expressing inflammatory macrophages, and disruption of IL-27 or its receptor in bone marrow-derived cells reduced PD-1+ CD8+ T cells and their effector functions. These findings define a novel mechanism for sustaining autoreactive T cells in the liver via TLR9-driven macrophage-induced IL-27 circuit that sustains a functional, self-renewing autoreactive PD-1+ CD8+ T cell program in situ.

Vaccination generates heterogenous B cell responses that collectively provide protective immunity, yet how this diversity is established remains poorly understood. Here, we identify the draining lymphatic network as a spatial organizer of humoral immunity. Vaccine dispersal across interconnected draining lymph nodes (dLNs) establishes gradients of antigen and inflammation that create distinct B cell differentiation and selection environments. dLNs proximal to the vaccination site preferentially support antibody-secreting cells and clonally diverse germinal center (GC) responses. In contrast, distal dLNs impose more stringent selection, favoring clonally restricted GCs enriched for high-affinity B cells. Spatially distinct inflammatory environments further determine antibody isotype, linking LN position to antibody effector class. These spatial biases persist upon recall and can be reprogrammed through vaccine design, including nanoparticle properties and LN-directed targeting. Thus, lymphatic networks diversify B cell fate, repertoire and affinity selection, and antibody isotype, revealing a programmable axis for tuning humoral immunity through vaccine design.

Tissue microenvironments differ widely in nutrient composition; yet how local nutrient conditions shape epigenetic programs that direct immune cell fate is poorly understood. We identify histone lysine propionylation (Kpr) as a chromatin mechanism linking nutrient availability to T cell fate decisions. Proteomic analysis reveals that Kpr is broadly reduced in exhausted T cells. H3K18pr is enriched at stemness-associated loci in effector T cells and depleted upon exhaustion. Isoleucine and propionate supply propionyl-CoA in T cells, and restricted nutrient availability within the tumor microenvironment limits histone Kpr, promoting T cell exhaustion. Disrupting isoleucine catabolism in T cells further suppresses Kpr, without altering histone acetylation, and impairs T cell function and antitumor immunity in a manner rescued by propionate. Dietary supplementation of isoleucine and propionate increases Kpr in tumor infiltrating lymphocytes, limits exhaustion, and improves tumor control. These findings establish a microenvironment-chromatin axis crucial for antitumor immunity and amenable to nutritional intervention.

Tertiary lymphoid structures (TLS) predict response to checkpoint inhibition, and conventional dendritic cells (cDC) are required to build and maintain them. What renders a niche permissive for their assembly is unknown: chemokines recruit the cellular constituents but do not specify how they organize. Here we show that the organizing signal is a matrix fragment. Proteolysis of the proteoglycan versican (VCAN) releases the matrikine versikine, constitutively in germinal center light zones and inducibly in tumor stroma. Versikine activates CD11b+ cDC and expands cDC1 to assemble TLS-archetypal triads, apposed DC: CD4+ T: CD8+ T units. Versikine-conditioned DC engage progenitor-exhausted CD8+ T cells (Tpex) and Th1-polarized follicular helper CD4+ T cells. Excess unproteolyzed VCAN inverts this toward DC-Treg crosstalk and Tpex loss. Versikine supplied as mRNA or recombinant protein sensitizes refractory tumors to PD-L1 blockade. VCAN proteolysis prospectively predicted outcomes after PD-1 blockade in metastatic colorectal cancer. Matrikines organize chemokine-recruited cells into functional immune niches.

Rheumatic diseases, including rheumatoid arthritis (RA), spondyloarthritis (SpA) and osteoarthritis (OA), show distinct phenotypes yet respond to overlapping therapies, implicating shared immune mechanisms. In the Transimmunom cohort, we profiled peripheral blood from 240 individuals (47 healthy, 44 OA, 91 RA, 58 SpA) across deep immunophenotyping, immunoproteomics and Treg-Teff transcriptomics. Single-layer analyses revealed broader Treg than Teff remodeling, along with a shared pattern of reduced activated Tregs and expanded Helios+ Tregs across all diseases, alongside a decrease in functional Treg subpopulations, including CTLA4+ and CD45RA- Tregs. In RA specifically, LAG3+ Tregs were also expanded. Combining omics layers outperformed single-layer approaches for disease classification. Among individual layers, Treg transcriptomes were most discriminative, and integration uncovered disease-specific programs. Unsupervised clustering identified a cross-disease cluster independent of activity, treatment and age, mapping to early disease (<= years) and dominated by a Treg dysfunction-associated program. These results provide a biological rationale for the therapeutic "window of opportunity" concept and duration-stratified Treg-directed trials.

Lymphocyte activation gene-3 (Lag3) is an inhibitory receptor that limits effector T cell activation and function. We previously demonstrated that Lag3 supports regulatory T (Treg) cell function through Myc-dependent metabolic reprogramming. However, the intracellular mechanisms underlying this regulation remain incompletely understood. Here, we generated mice with Treg-specific deletion of the Lag3 KIEELE motif and demonstrated that this motif is required for Treg-mediated suppression of autoimmune inflammation. Loss of the Lag3 KIEELE motif led to enhanced TCR/PI3K-Akt/MEK-ERK signaling and Myc expression, accompanied by increased glycolytic activity and acquisition of effector T cell-like features. We also identified that hematopoietic progenitor kinase 1 (HPK1) and Cbl-interacting protein of 85 kDa (CIN85) associate with Lag3 through the KIEELE motif. HPK1 depletion partially recapitulated the phenotypic changes and impaired Treg suppressive function in vivo. Together, these findings identify the KIEELE motif as a critical link between Lag3-associated signaling machinery and metabolic regulation that sustains Treg suppressive function during autoimmune inflammation.

Intestinal V{gamma}4 {gamma}{delta} intraepithelial lymphocytes (IELs) persistently bind the constitutively expressed epithelial ligand BTNL3/8 through germline-encoded T cell receptor (TCR) determinants. While they resemble innate-like T cells such as NKT cells, unlike these populations, V{gamma}4 IELs encounter ligand only after thymic development. Moreover, unlike conventional {beta} T cells, V{gamma}4 IELs sustain persistent physiological ligand engagement without becoming exhausted. Here, using biophysical, functional, and multimodal single-cell approaches, we show how V{gamma}4 IELs address this challenge. While germline-encoded TCR regions broadly mediate BTNL3 recognition, productive activation requires additional non-germline TCR features that license responsiveness to BTNL3/8 and enable local selection in the gut. Rather than driving exhaustion, BTNL3/8 reactivity directly promotes expression of an NK-like program marked by adaptor molecules that license innate-like signaling in healthy tissue. These findings reveal how combined innate and adaptive features of the {gamma}{delta}TCR enable durable tissue specialization under conditions of persistent physiological ligand engagement.

T cells persist in the central nervous system (CNS) and can drive both protection and neurological disease. How these cells are organized in humans and what they recognize is largely unknown. Here, we profiled CD8 T cells across anatomically distinct CNS regions, obtained through on-site autopsies and temporal lobe resection surgeries, using single-cell RNA sequencing, paired T cell receptor sequencing, and DNA-barcoded tetramers. Resident memory T cells (TRM) specific for Epstein-Barr virus, cytomegalovirus, influenza A, and SARS-CoV-2 were identified across CNS compartments. Anatomical location was the strongest correlate of TRM cell state, with leptomeningeal cells adopting a cytokine-poised TRM program, whereas brain TRM cells were transcriptionally restrained. Cells of the same clonotype spanned tissues yet adopted local transcriptional states. Viral specificity added another layer of TRM heterogeneity with GZMK/GZMA-expressing EBV-specific populations and interferon-stimulated gene signatures in SARS-CoV-2 and Influenza A-specific cells. The human CNS thus harbors regionally distinct CD8+ TRM shaped by common viral exposures.

Decoding which antigens activate a given T cell receptor (TCR) is a central challenge in immunology. We present SEEKER, a functional genome-scale library-on-library screening platform built on three elements: a Jurkat-derived T-APC cell (TAPCell) that combinatorially expresses one TCR and one peptide-MHC drawn from separate libraries together with an NFAT activation reporter; encapsulation of single TAPCells in a thermos-reversible hydrogel for isolated clonal expansion, so recognition is read out as intraclonal activation; and dual-asymmetric PCR that links TCR- and pMHC-encoding sequences into a heritable unit, enabling progressive hit enrichment over screening rounds. SEEKER interrogates ~10^8 TCR-pMHC combinations per run without prior knowledge. Screening joint-infiltrating CD8+ T cells from HLA-B*27+ ankylosing spondylitis patients against proteome-wide libraries validated 53 TCR-peptide pairs, uncovered extensive cross-recognition of self and common viral epitopes, and revealed highly polyreactive T cells recognizing up to 80 autoantigens, implicating virus-triggered poly-autoreactivity in multi-organ autoimmune diseases.

The bronchial epithelium in asthma is vulnerable to damage and has impaired barrier function, but the mechanisms by which it contributes to airway inflammation and remodelling remain unclear. Here, we dissect these epithelial and immunological disease mechanisms by establishing a comprehensive single cell atlas of the bronchial wall from 21 patients with childhood-onset asthma and 25 matched healthy controls. We identify a novel asthma-associated non-canonical epithelial differentiation trajectory in which a repair-associated KLF4+ basal cell subset differentiates into KRT13+ hillock-like cells through a proliferative KRT14+ intermediate. In vitro cultured matched primary bronchial epithelial cells show that this trajectory is retained in absence of exogenous factors. We find that IL-13 induces hillock-like cell differentiation into CEACAM5hi goblet cells, driving goblet cell metaplasia. Repair-associated basal cells and transitioning CEACAM5hi hillock-like cells strongly contribute to airway inflammation and remodelling. In turn, dendritic cells and mast cells promote a state of highly active epithelial differentiation, which shows increased multiciliated cell fate decisions, in concordance with an increase in multiciliated cell death observed in asthma. Proportions of the epithelial cells of the non-canonical differentiation trajectory are associated with clinical outcomes such as disease severity, FeNO, and small airway function.

Pathogenic T helper 17 (pTH17) cells are a subset of CD4+ T cells driving autoimmune diseases including multiple sclerosis (MS). Compared to homeostatic TH17 cells and other TH subsets, pTH17 have enhanced mitochondrial function and oxidative phosphorylation (OXPHOS) that supports their differentiation and pathogenic function. Here we identify Copper Transporter 1 (CTR1), encoded by Slc31a1, as essential for copper uptake in CD4+ T cells, OXPHOS and pTH17 cell differentiation and function. While copper levels are known to be higher in the cerebrospinal fluid of patients with MS compared to healthy individuals, and excess copper contributes to oligodendrocyte loss in murine models of MS, the effect of copper on T cell function and pathogenicity in MS are unclear. We demonstrate that deletion of Slc31a1 in CD4+ T cells decreased intracellular copper levels, disrupting mitochondrial respiration and rewiring metabolism. These changes altered the epigenetic landscape of pTH17 cells by impairing DNA demethylation capacity, leading to hypermethylated DNA and altered chromatin accessibility at key binding sites for AP-1 transcription factors essential for pTH17 differentiation. As a result, CTR1-deficient T cells showed defective differentiation into pTH17 cells, with decreased production of IL-17A and expression of TH17 signature genes, while the differentiation of other CD4+ T cell subsets remained largely unaffected. Moreover, T cell-specific deletion of Slc31a1 protected mice from central nervous system (CNS) inflammation in the experimental autoimmune encephalomyelitis (EAE) model of MS by suppressing clonal expansion of autoreactive CD4+ T cells. These findings establish copper as a critical regulator of pTH17 differentiation and function, revealing a previously unknown molecular link between copper homeostasis, metabolism and epigenetic regulation governing pTH17-mediated autoimmunity.

Cytoplasmic DNA sensing triggers intense innate immune responses that require tight regulation. PPAR{gamma} is a master metabolic regulator in macrophages, but its role in cytoplasmic DNA immunity remains unclear. Using poly(dA:dT) to mimic cytoplasmic DNA stimulation, we combined transcriptomics, epigenomics (PPAR{gamma}/H3K27ac ChIP-seq), and functional assays. Poly(dA:dT) induced a cytokine storm with MAPK activation and apoptosis/necrosis. PPAR{gamma} activation by rosiglitazone (RGZ) antagonized this response, reducing cell death and transcriptionally inhibiting MAPK genes (e.g., DUSP4/10). Mechanistically, PPAR{gamma} bound promoters/enhancers via PPRE motifs and distal intergenic regions, remodeling H3K27ac (reduced at inflammatory loci, increased at metabolic genes). RGZ induced de novo super-enhancers coupling PPAR metabolic programs (e.g., CPT2) with immune suppression by targeting TLR4, CEBPB, and PIM3. Thus, PPAR{gamma} acts as a brake in cytoplasmic DNA immunity, integrating metabolic reprogramming and inflammation suppression through a multi-level genomic/epigenetic program. This study highlights PPAR{gamma} as a key immune-metabolic integrator and therapeutic target for diseases driven by excessive cytoplasmic DNA sensing.

Systemic iron sequestration occurs frequently in cancer due to inflammation-driven expression of the iron-regulatory hormone hepcidin. The impact of systemic iron availability on tumoral immunity is unclear. Here, we show that elevated serum hepcidin is associated with reduced survival and decreased intratumoral CD8+ T cells in patients with pancreas cancer. While hepcidin is not induced in murine tumor models, administration of a hepcidin mimetic phenocopies the T-cell-depleted tumor microenvironment seen in patients. Mechanistically, chronic antigen-driven mitochondrial dysfunction disrupts iron metabolism and selectively depletes high avidity CD8+ T cells during iron restriction. These findings establish a direct link between hepcidin-mediated iron sequestration and tumoral immunity and nominate systemic iron dysregulation as a therapeutic target to enhance anti-tumoral CD8+ T cell responses.

Systemic lupus erythematosus (SLE) is the prototypical systemic autoimmune disease defined by the production of autoantibodies directed against diverse self-antigens. Antinuclear antibodies (ANA) are central to SLE diagnosis, and anti-double-stranded DNA (anti-dsDNA) antibodies are clinically used to track disease activity. However, these biomarkers provide only partial insight into the full spectrum of autoimmune changes in patients. To expand the known landscape of SLE autoreactivity shared among patients and associated with disease activity, we performed an unbiased characterization of 1,268 SLE plasma samples from 695 SLE patients and 301 healthy controls using phage immunoprecipitation and sequencing (PhIP-seq). This technique preferentially displays linear epitopes, and thus provides a complementary set of autoreactivities to previously discovered autoreactive targets. Despite the marked clinical heterogeneity of SLE, machine learning applied to this data surfaced a shared, reproducible signature that robustly discriminates between SLE and healthy controls in two validation cohorts. Autoreactivities in SLE were significantly enriched for RNA-binding protein targets. Autoreactive proteins containing Basic Acidic Dipeptides (BAD) repeat domains, features associated with biomolecular condensate formation, distinguished patients with high disease activity (by SLEDAI score) from patients with no disease activity. Among all shared autoreactivities, a peptide derived from YTHDF2 emerged as the most prevalent target across SLE cohorts occurring in ~25% of SLE patients and displayed striking sequence similarity to a peptide derived from the Epstein Barr virus (EBV) lytic switch protein BZLF1. Competition assays demonstrated higher-affinity binding to the viral peptide, supporting a model in which antiviral humoral responses to EBV may drive secondary epitope spreading toward molecularly mimicked self-antigens. Remarkably, orthogonal validation using the Luminex bead platform containing a panel of only 10 peptides, including BZLF1, demonstrated strong discrimination between SLE and healthy controls (AUC = 0.95). Together, these findings identify a rich, greatly expanded landscape of autoreactivities in SLE, candidate biomarkers associated with high disease activity, and provide mechanistic insight linking EBV-driven immunity to epitope-specific autoimmunity in lupus.

Natural killer (NK) cells and type 1 innate lymphoid cells (ILC1s), collectively known as group 1 innate lymphoid cells (ILCs), are critical mediators of anti-tumor immunity, yet their role in brain metastasis remains poorly defined. Using single-cell RNA sequencing and functional depletion models, we show that group 1 ILCs fail to provide adequate tumor control in breast cancer brain metastasis (BCBM). In contrast to the liver, where diverse, functionally competent group 1 ILC populations facilitate excellent metastatic control, group 1 ILCs in BCBM show limited diversity and profound tissue-specific dysfunction such that their depletion had no effect on tumor burden despite modest parenchymal infiltration. We attribute this group 1 ILC dysfunction to severely restricted IL-15 availability, with IL-15R protein detected at 500-fold lower concentration in the brain than in the liver. Local IL-15 complex administration restored group 1 ILC accumulation, cytotoxicity, and tissue residency, significantly reducing brain metastatic burden independent of T cells. Intracranial delivery of IL-15-secreting induced pluripotent stem-cell-derived (iPSC)-NK cells, already in clinical testing for non-small cell lung cancer, significantly reduced tumor burden. Collectively, these findings reveal how tissue-specific differences in cytokine availability shape group 1 ILC population diversity and disease response, establishing localized IL-15 signaling as a compelling strategy to unlock innate immunity against intracranial malignancies.

Human leukocyte antigen B*27 (HLA-B*27) is a major risk factor for autoimmune diseases such as axial spondyloarthritis (axSpA), acute anterior uveitis (AAU), and psoriatic arthritis (PsA). HLA-B*27 presents bacterial and self-antigens to disease-associated CD8+ T cells, however, how this leads to a pathogenic IL-17-mediated disease remains unclear. We performed mutational experiments in an established disease-associated TCR and demonstrated that the pathogenic motif encompasses a wider range of TCR sequences than previously appreciated. We next leveraged computational pairing of alpha/beta TCR sequencing (TCR-seq) to demonstrate that the broadened pathogenic motif distinguishes axSpA and AAU patients from healthy controls. Paired single-cell RNA sequencing and single-cell TCR sequencing datasets demonstrated that the pathogenic cells have a distinct transcriptional signature. We find a coupling of pathogenic TCRs to this transcriptional signature in public datasets from axSpA and PsA joint fluid and AAU ocular fluid. Finally, we detect the pathogenic CD8+ T cells in the gut and demonstrate that they express a Type 17 program. Our findings suggest that HLA-B*27+ axSpA, AAU, and PsA are initiated by HLA-B*27-restricted pathogenic CD8+ T cells that undergo Type 17 differentiation in response to intestinal antigens.

Ectopic lymphoid structures are typically associated with chronic tissue inflammation in autoimmunity and cancer, where they can amplify local immune responses. Similar structures arise spontaneously with age, yet their origin and function remain unclear. Here we identify tissue retention of mature migratory conventional dendritic cells (cDCs) as a driver of age-associated lymphoid organization. Mature cDCs accumulated within lymphoid structures in aged human and mouse tissues. We demonstrate that impaired cDC egress or pharmacological cDC expansion induced de novo structures in mice across multiple otherwise homeostatic organs without associated pathology. Strikingly, senescence-associated tissue cues, which promoted a distinct cDC maturation state, were required for lymphoid niche initiation. Unlike inflammatory structures described in disease, these cDC-driven structures preferentially accumulated tissue-adapted regulatory T cells and protected against inflammatory injury, revealing a previously unrecognized regulatory dimension of age-associated lymphoid organization.