Project Summary:
Innate-like ¿d 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 ¿d T cells is their ability
to rapidly produce large amounts of cytokines (e.g., IFN-¿, 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 ¿d T cells exhibit innate-like T cell characteristics, evidence in both mouse and humans
indicates the presence of naïve, unpolarized ¿d T cells. The mechanisms/pathways that confer an innate-like
phenotype on developing ¿d 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 ¿dT 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 ¿d V(D)J profiling platform and
scATACseq to define the gene regulatory programs that distinguish SAP-dependent innate-like ¿d T cells during
development. Our preliminary data suggest that the SLAM/SAP signaling pathway functions at a very early stage
of ¿d T cell development, is involved in shaping the ¿d TCR repertoire, and reveals the presence of SAP-
dependent ¿d TCR clonotypes. Altogether, these published and unpublished lead us to hypothesize that
SLAM/SAP signaling regulates the development of functionally distinct innate-like ¿d TCR clonotypes. To test
this hypothesis, we will i) define the gene regulatory programs that distinguish SAP-dependent and SAP-
independent thymic ¿d T cells during development and ii) define the mechanisms through which SLAM/SAP
signaling regulates innate-like ¿d T cell developmental and function. Upon completion of these Aims, we expect
to have defined new SAP-dependent innate-like ¿d T cell subsets and to have generated a comprehensive map
of the SAP-dependent gene regulatory programs of ¿d 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 ¿d 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.