SMAD7-Mediated Modulation of TGF-β Signaling Drives the Emergence of ex-Tissue-Resident CD8 T Cells in Autoimmune Uveitis 2259507

Abstract Introduction Tissue-resident memory T cells (TRMs) maintain local immune surveillance, yet their persistence and potential for egress during autoimmune inflammation remain unclear. In autoimmune uveitis, recurrent flares imply dynamic circulation between the inflamed eye and peripheral blood. We hypothesized that dysregulation of TGF-β signaling within ocular TRMs could impair tissue retention and promote their release as circulating ex-TRM cells. Methods We performed paired single-cell RNA sequencing of vitreous and peripheral blood mononuclear cells from patients with autoimmune uveitis, focusing on shared TCR clones to delineate tissue—circulation transitions. Transcriptomic findings were validated by flow cytometry, cytokine assays to retinal autoantigen (IRBP), and antisense oligonucleotide knockdown of candidate signaling regulators. Results Shared CD8 T cell clones exhibited distinct compartmental signatures: vitreous clones expressed TRM-associated genes (CD69, ITGAE, ITGA1, CXCR6, ZNF683) and TGF-β—responsive regulators (PMEPA1, SMAD7), while circulating members re-expressed S1PR1, CCR7, and cytotoxic mediators, defining an ex-TRM phenotype. Flow cytometry confirmed CD8 ex-TRM and, to a lesser degree, CD4 ex-TRM cells in blood that responded to IRBP stimulation. Vitreous TRMs expressed higher SMAD7 and PMEPA1 than their circulating counterparts. SMAD7 silencing restored CD103 (ITGAE) expression, suggesting that SMAD7-mediated inhibition of TGF-β signaling reduces epithelial anchorage. Conclusion Our data reveal that SMAD7 suppresses TGF-β—driven retention cues, facilitating TRM egress from the eye into circulation as ex-TRM cells. This SMAD7—TGF-β axis defines a mechanistic link between tissue residency, egress, and systemic autoreactivity in autoimmune uveitis, highlighting a potential target for modulating chronic tissue inflammation. Funding Source DBT Wellcome Trust India Alliance, Hyderabad Eye Research Foundation Topic Categories Immune Mechanisms of Human Disease (HUM)