Project summary The highly specialized intestinal immune system is charged with maintaining tolerance to harmless stimuli from food and commensal bacteria, while providing protective immunity against pathogens. Dysregulation of this critical balance can lead to food allergy, inflammatory bowel disease (IBD), or increased susceptibility to enteric pathogens. Dendritic cells (DCs) are key players in intestinal homeostasis, finely orchestrating immune responses by presenting luminal antigens and inducing functional differentiation of CD4+ T cells into regulatory or pro-inflammatory subsets. The cellular mechanisms underlying the decision between tolerance or immunity to intestinal antigens remain unknown, largely because the identification and characterization of the exact DCs involved in these processes has been a decades-long technical challenge. To overcome this problem, I established the use of the LIPSTIC (Labeling Immune Partnerships by SorTagging Intercellular Contacts) technology in the gut, which enables proximity-dependent labeling of specific intestinal cell-cell interactions. The main goal of this research proposal is to elucidate the mechanisms that determine whether DCs will induce regulatory or pro-inflammatory T cells in vivo, by combining the LIPSTIC system with gene targeting, functional imaging, intersectional genetics, and interaction-based transcriptomics approaches. This proposal tests the hypothesis that DCs specialized for different functions exist in the intestine and that continuous dynamic reprogramming of DCs subsets by luminal content dictate tolerance or immunity to food and microbes. Specifically, this concept will be tested in mice under physiological (tolerance to food and microbes) and pathological (allergic sensitization, enteric infection, and colitis) scenarios. To this end, the K99 mentored phase (Aim 1) will reveal the exact nature of the DCs that induce tolerance or inflammation to food and the cellular and molecular mechanisms by which food-specific pTregs maintain oral tolerance. Next, the R00 independent phase (Aim 2) will focus on studying immune responses to commensals, with relevance to disorders such as colitis. Elucidating the DC populations, location and molecular mechanisms involved in tolerance to distinct microbes will reveal the nature of host-microbe interactions in health and disease. Together, this research program will lend fundamental insight into the etiology of certain intestinal disorders and will provide foundation for the development of new therapies for food allergy, colitis, and enteric infections, with profound implications for public health. The proposed development plan complements my training in mucosal immunology and cellular interactions with transcriptomics analysis, imaging, and mouse genetics. I will take advantage of the extensive resources of the Rockefeller University, the mentorship of Dr. Daniel Mucida, Dr. Gabriel Victora and the Advisory Committee team that will lend expertise in key aspects of the project and career development. At the end of the mentored phase, I will be equipped with the necessary tools to conduct comprehensive studies at the intersection of cellular communication and immune response to commensals as an independent investigator.

Project narrative Dysregulated mucosal immune responses to dietary or microbial antigens can cause severe diseases. The main goal of this research program is to study the nature of immune cells communication that dictates tolerance or inflammation to food and microbes. This work will provide both a new perspective for the understanding of intestinal disorders and a foundation for the development of new therapies targeting specific cells, genes, and pathways.