Project Summary This proposal centers on a novel super-enhancer that we initially discovered to coordinate a non-prototypical T cell response in which effector T cells are triggered to produce the key type 1 cytokine interferon gamma (IFN- g), independently of the T cell receptor, via stimulation with precise cytokine combinations that are known to activate certain innate immune cells. In particular, effector T cells synthesize IFN-g in response to a STAT- activating cytokine (IL-2 or IL-12) plus an IL-1 family member (IL-33, IL-36 or IL-18). Although such "innate-like" T cell responses have not been extensively studied, they have been shown to facilitate host defense against various infections, and may also boost cancer immunotherapy. In analyzing the molecular mechanisms underpinning innate-like T cell responsiveness, we identified a novel super-enhancer on mouse chromosome 1 that facilitates STAT-activating cytokine-mediated transcription of the genes encoding the receptors for IL-33 and IL-18. Importantly, human GWAS studies identified SNPs in this region (on human chromosome 2) linked to the IL-33-regulated pathologies asthma and allergy as well as lung cancer. Further, we generated a novel CRISPR-Cas9 genome-edited mouse lacking this super-enhancer, whose conventional CD8 and CD4 T cells have impaired innate-like capacity. Additionally, Foxp3+ T regulatory cells lacking the super-enhancer exhibit reduced expression of the IL-33 receptor, that is known to confer suppressor function. These global super- enhancer knockout mice also exhibit slower rates of tumor growth in the absence of immunotherapy, as well as increased resistance to endotoxin shock, suggesting that the super-enhancer may also regulate the function of additional immune cell types. This project will generate a novel conditional super-enhancer knockout mouse strain that will facilitate studies to precisely define the role of the super-enhancer in different immune cell types and physiologic and therapeutic settings impacted by IL-33 or IL-18.