DENDRITIC CELL-SPECIFIC IL-36 RECEPTOR DEFICIENCY AMELIORATES COLONIC INFLAMMATION IN COLITIS

Abstract INTRODUCTION Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn’s disease (CD), is a chronic, life-threatening disorder of the gastrointestinal tract that often arises during childhood. Pathogenesis is driven by dysregulated immune responses and inflammatory cytokine signaling, including interleukin-36 (IL-36)/IL-36 receptor (IL-36R) pathways. Work from our laboratory and others has demonstrated the key role of IL-36 cytokines and their signaling in the pathogenies of ulcerative colitis both in humans and preclinical mouse models. IL-36R regulates innate and T cell immunity, and IL-36 ligands are known to modulate dendritic cell (DC) functions, highlighting the importance of investigating their role in UC. Here, we aimed to investigate the specific role of IL-36R in mediating DC responses in IBD pathogenesis. Approach and Results We first analyzed single-cell RNA sequencing (scRNA-seq) datasets and colon biopsies from UC patients to assess IL-36R expression on gut-resident immune cells. Transcriptomic analysis revealed high IL36R expression in classical DC (cDC) subsets in UC, while digital spatial profiling of colon biopsies showed increased IL-36R expression in the lamina propria and barrier-adjacent regions, correlating positively with gut-resident DC markers (CD11c, CD103). Based on these findings, we generated cDC-specific Il36r knockout mice (Il36rΔcDC) to determine the role of IL-36R signaling in cDCs during experimental colitis. Age-matched, littermate controls were administered 2% dextran sulfate sodium (DSS) for 5 days and sacrificed on day 7. Il36rΔcDC mice were markedly protected from DSS-induced acute colitis, exhibiting reduced disease activity index, less body weight loss, reduced colon shortening, decreased inflammatory gene expression, and improved histology compared to wild-type counterparts. Under homeostasis, no baseline microbiome alterations were observed in Il36rΔcDC mice. However, RNA sequencing of colon tissue revealed upregulation of pathways linked to immune tolerance and barrier protection, including antigen processing and presentation, retinol metabolism, and mitogen-activated protein kinase signaling. These findings suggest that IL-36R deficiency in cDCs shapes the colonic microenvironment critical for barrier function and tolerance. CONCLUSION Collectively, our data indicate that IL-36R signaling is altered in colonic cDCs of UC patients and that IL-36R deletion in cDCs protects mice against acute colitis, supporting further exploration of IL-36R-targeted therapies in UC.