Project Summary/Abstract “Necroptosis” is a form of cell death with roles in host defense, autoimmunity, and cancer. Necroptosis is associated with inflammation and immunity, but how cells in which the necroptotic pathway is active alter the immune response is poorly understood. Much of the prior research in this area has focused on the role of lytic cell death and the release of “DAMP” molecules in necroptosis-induced inflammation. However, recent work from our group and others has highlighted key roles for proteins of the necroptotic pathway—including RIPK1 and TRIF—in activating inflammatory transcription programs, and has demonstrated that activation of “necroptosis” can drive cytokine production in the absence of cell death in some settings. The work proposed here will test the hypothesis that transcriptional signaling, not lytic cell death, represents the most immunologically significant output of the “necroptotic” pathway, and that necroptotic cell death may actually reduce inflammation by eliminating cells in which inflammatory transcription programs are active. To do this, we will focus on thee Aims: First, we will define the interactions and transcription programs activated by necroptotic pathway components in cultured cells, using engineered proteins and natural ligands. Second, we will study the role of necroptosis pathway activation in vivo, by delivering engineered, constitutively active forms of necroptosis inducers to the lung epithelium of mice. Third, we will evaluate the roles of necroptotic transcription and cell death in the immune response to influenza A virus, a potent activator of the necroptotic pathway. The work proposed here will use novel experimental tools to understand the immune response to “necroptosis” in vivo. Given the emerging roles of this pathway in infection, autoimmunity and cancer, and the substantial efforts underway to target it therapeutically, we suggest that these studies are timely and potentially impactful.