PROJECT SUMMARY My long-term career goal is to do hypothesis-driven research as an independent investigator at a university spanning basic and clinical immunology in inflammatory bowel diseases (IBD). In order to achieve this goal, I have put together an advisory team composed of Dr. Matthew Olson (sponsor), Dr. Timothy Ratliff (co-sponsor), Dr. Tzu-wen Cross (collaborator), Dr. Majid Kazemian (collaborator), Dr. Shihuan Kuang, and Dr. Wayne Campbell to provide technical training for in vitro cell culture techniques, in vivo mouse models of intestinal disease, and gnotobiotic training, as well as other professional development skills in scientific writing and communication. My preliminary work outlined in this proposal has demonstrated that mice with conventional T cell-specific deletions in two important T cell transcription factors, STAT3 and BATF, developed an aggressive spontaneous colitis that was marked by a dysregulated microbiota and elevated numbers of γδ T cells in the intestines similar to what is observed in human patients. Given that the current treatment options available for IBD are not fully effective in long term treatment, my data indicate that disrupting this STAT3/BATF-axis through targeting the dysregulated gut microbiota or γδ T cells may represent a novel therapeutic strategy. To further understand this complex relationship between dysregulated gut microbiota and non-conventional γδ T cells in IBD-like colitis, this proposal will address the following: (1) Elucidate the role of the microbiota in regulating intestinal γδ T cell homeostasis during intestinal disease. 16S rRNA sequencing will be used to define shifts in the microbial community in each mouse genotype. To determine if this microbiota is required and sufficient to induce γδ T cell responses and disease we will treat animals with antibiotics and perform fecal microbiota transfers into germ-free animals, respectively. (2) Determine the role of γδ T cells in driving IBD. Therapeutically, I will treat mice with monoclonal antibodies that block γδ T cell receptor activation and monitor its impact on inflammatory responses in the intestines and clinical disease development. In order to determine if γδ T cells can confer disease, I will isolate γδ T cells from Stat3fl/flBatffl/flCd4Cre+ mice and transfer them into colitis susceptible (Rag-/-) mice. The results of this proposal will further elucidate the role of γδ T cells in Stat3fl/flBatffl/flCd4Cre+ mice, which may serve as useful model to study γδ T cells in IBD-like colitis. Given that current therapies for IBD patients are only partially effective, the resulting data from this study and the establishment of this unique mouse model of γδ T cells in IBD-like colitis will potentially identify novel therapeutic targets to make a positive impact on the 6.8 million people living with IBD worldwide.