DESCRIPTION (provided by applicant): This renewal application seeks support for the continuation of our studies designed to elucidate the regulatory programs of dendritic cell subsets that are required for antimicrobial host defenses in the intestine. We recently discovered a cellular circuitry, whereby mucosal DCs interact with the fenestrated capillary vessel system of the small intestine for the sampling of antigens that transition from the blood circulation through the lamina propria into the intestinal lymphatic system and the control of mucosal inflammation. The integration of luminal and circulatory antigen surveillance in the SI indicates that mucosal dendritic cells and macrophages could receive microbial signals that originate outside the intestine and that intestinal pathogen recognition could impact peripheral immune responses. The focus of this proposal will be the foreign nucleic acid recognition pathways in mucosal Zbtb46+ DCs that include distinct classical DC subsets that can induce IL-17 expressing T helper cells (Th17) cells in the mucosal immune system but also drive inducible T regulatory cell development and IL-10 expression. Defining these pivotal mechanisms is important for strategies that can control intestinal inflammation but also for the understanding of the impact of mucosal immune responses on the peripheral immune system and extra intestinal manifestation of inflammatory bowel diseases.

PUBLIC HEALTH RELEVANCE: A detailed understanding of sensing of microbial components by dendritic cells in the intestine for the induction of host defenses or tolerance is critical for strategies to curtail mechanisms that impede or exacerbate mucosal immune responses leading to Inflammatory Bowel Diseases. We aim to unravel mechanisms that control the differentiation of mucosal dendritic cells for the regulation of host defenses against viral and bacterial pathogens by elucidating the transcriptional programs that determine T cell polarization in the intestinal mucosa and mesenteric lymph nodes.