Deciphering the immunogenicity of cell death using systematic genetic tools

Project Summary Professional phagocytes, including macrophages and dendritic cells, engulf approximately 200 billion dead cells per day in humans. The vast majority of dead cells are consumed “silently,” in that the phagocyte does not trigger an adaptive immune response targeting the material in the engulfed cell, thereby maintaining tolerance of self. Phagocytes play a critical role in maintaining self-tolerance, and their accurate decision-making during phagocytosis is essential for avoiding catastrophic immune rejection of self antigens. On the other hand, immunogenic cell death (ICD), in which an engulfed cell is interpreted as having died following infection with a pathogen, is critical for launching an effective immune response against viral pathogens and tumors. The immunogenicity of pathogen-induced cell death is known to depend on the detection of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRR) in phagocytes. By contrast, the mechanisms governing the regulation of ICD in sterile contexts (such as autoimmunity and cancer) are significantly less well understood. Our lack of knowledge of the molecular signals that govern ICD directly impedes our ability to develop rational therapeutic strategies to either trigger or suppress ICD. We argue that the absence of systematic genetic tools for understanding this complex, inter-cellular process has critically hindered the progression of the ICD field. We propose a systematic approach for investigating the mechanisms governing ICD, building on our recent development of a suite of platforms for high-throughput interrogation of the genetics of myeloid cell biology. We will focus our efforts on three key “blind spots” in our knowledge of the three sequential stages of ICD: 1) the mechanism of calreticulin-independent cellular uptake, 2) the mechanism of DAMP/adjuvant release by dead cells, and 3) the mechanisms governing PRR-driven antigen presentation in APCs. The project is designed to have high impact by providing the first systematic investigations of this core immunological process and by potentiating therapeutic targeting of these pathways in autoimmunity, cancer, and infectious diseases.