BHLHE40 Orchestrates ILC3 and RORγt+ APC-Mediated Barrier Immunity 2309149

Abstract Introduction A central feature of the intestinal immune system is its ability to protect against pathogens while maintaining tolerance to commensal microbiota. Group 3 innate lymphoid cells (ILC3s), which express the transcription factor RORγt, produce effector cytokines such as IL-22 that are essential for epithelial repair and barrier restoration. Recent studies have identified a subset of RORγt+ antigen-presenting cells (APCs) that promote peripherally induced regulatory T cell (pTreg) responses in the intestine. However, the molecular mechanisms by which RORγt+ immune cells coordinate tissue protection and antigen-specific tolerance are not well defined. Here, we investigated the role of the transcription factor Bhlhe40 in regulating intestinal mucosal immunity. Methods Bulk and single-cell RNA sequencing were used to define Bhlhe40-dependent transcriptional programs in ILC3s and RORγt+ APCs. Innate colitis and Helicobacter hepaticus-specific T cell transfer models were used for assessing the function of Bhlhe40 in vivo. Results We identified Bhlhe40 as a central regulator of both ILC3- and RORγt+ APC-dependent mucosal immunity. TNF-like ligand 1A (TL1A) stimulation and colitis enhance intestinal ILC3s expression of Bhlhe40 in mice and humans. Basal Bhlhe40 expression in ILC3s is essential for efficient transcription of cytokine effectors and maintenance of mucosal immunity, whereas TL1A-induced upregulation of Bhlhe40 further amplifies these effects by epigenetic imprinting. Mechanistically, Bhlhe40 regulated expression of the co-stimulatory molecule Tnfsf4 (OX40L) on ILC3s, supporting the induction and maintenance of Helicobacter hepaticus-specific Tregs. Bhlhe40 is also highly expressed in RORγt+ APCs and required for the expression of maturation markers as well as optimal generation of antigen-specific Tregs and oral tolerance. Conclusion Our study reveals a central role for Bhlhe40 in shaping both intestinal ILC3 effector response as well as antigen-specific tolerance in shaping barrier immunity. Funding Source N/A Topic Categories Mucosal and Regional Immunology (MUC)