Project Summary: Innate-like γδ T cells are unusual T cells that are highly enriched in mucosal tissues like the lung, gut, and skin, where they play critical roles in the host immune response to pathogens, in autoimmunity, in anti- tumor immunity, and in tissue repair/homeostasis. A defining characteristic of innate-like γδ T cells is their ability to rapidly produce large amounts of cytokines (e.g., IFN-γ, IL-4, and IL-17), chemokines, and growth factors which allows them to shape both the magnitude and quality of both the developing immune response. Although a large fraction of γδ T cells exhibit innate-like T cell characteristics, evidence in both mouse and humans indicates the presence of naïve, unpolarized γδ T cells. The mechanisms/pathways that confer an innate-like phenotype on developing γδ T cells remain largely undefined. Both our recently published and preliminary data indicate that the SLAM/SAP signaling pathway is intimately involved in the development and function of innate- like γδT cells, and that it works through multiple distinct pathways. Here, w e p r o p o s e t o use a single-cell multiomics approach that includes scCITEseq coupled with a customized γδ V(D)J profiling platform and scATACseq to define the gene regulatory programs that distinguish SAP-dependent innate-like γδ T cells during development. Our preliminary data suggest that the SLAM/SAP signaling pathway functions at a very early stage of γδ T cell development, is involved in shaping the γδ TCR repertoire, and reveals the presence of SAP- dependent γδ TCR clonotypes. Altogether, these published and unpublished lead us to hypothesize that SLAM/SAP signaling regulates the development of functionally distinct innate-like γδ TCR clonotypes. To test this hypothesis, we will i) define the gene regulatory programs that distinguish SAP-dependent and SAP- independent thymic γδ T cells during development and ii) define the mechanisms through which SLAM/SAP signaling regulates innate-like γδ T cell developmental and function. Upon completion of these Aims, we expect to have defined new SAP-dependent innate-like γδ T cell subsets and to have generated a comprehensive map of the SAP-dependent gene regulatory programs of γδ T cells at different stages of development. In addition, we will have made a significant step forward in defining one of the mechanisms that regulates innate-like γδ T cell development and function. We believe this information will be a critical step forward in defining the developmental requirements that define these lineages as well as their specific contributions to the immune response.

Gamma delta T cells are unusual white blood cells that preferentially reside in mucosal tissues and play important roles in the immune response to pathogens, to cancer, and in autoimmunity. However, unlike their well-studied conventional alpha beta T cell counterparts, we still know very little about the mechanisms that regulate gamma delta T cell development and function. The focus of this proposal is to explore the mechanisms through which a family of receptors, called SLAM family receptors, regulates the developmental programming of different functional subsets of gamma delta T cells so that we can understand better the function of these cells in health and disease.