Washington University in St Louis St. Louis, Missouri, United States
Disclosure(s): No financial relationships with ineligible companies to disclose
Background/Purpose: Systemic lupus erythematosus is a chronic, multisystem autoimmune disease characterized by the dysregulated clearance of dying cells, which results in the release of damage-associated molecular patterns and intracellular targets of disease-associated autoantibodies. Dendritic cells are important mediators of ‘efferocytosis’ (the phagocytosis of apoptotic cells) and present apoptotic cell-derived autoantigens to CD4+ T cells via endocytic processing and MHC class II binding. Despite autoreactive T cells being essential to the pathogenesis and progression of diverse autoimmune diseases, there is only a nascent understanding of their autoantigen specificities. Prior studies have utilized almost exclusively model antigen systems (e.g. ovalbumin), without focus on cell death- and other inflammation-associated endogenous autoantigens. Methods: We have developed and validated a mass spectrometry-based approach to characterize apoptotic cell-derived peptide autoantigens presented by dendritic cells (the ‘efferocytic immunopeptidome’). Furthermore, we have developed a novel approach for testing T cell antigen recognition, using TCR-dependent expression of a fluorescent timer protein, that operates independently of cytokine production, proliferation or effector function. This approach will be used to define populations of autoreactive T cells during homeostasis and in multiple mouse models of lupus. Results: Our mass spectrometry studies have identified unique subcellular pools of antigens presented in the efferocytic immunopeptidome, including those of nuclear and ribosomal origin. Through our studies on T cell autoreactivity, we identify a small population of T cells from naïve and diseased mice that are reactive against the efferocytic immunopeptidome. Conclusion: Efferocytosis promotes the presentation of unique pools of cellular peptide antigens that represent a potential source of autoantigen and the driving of autoreactive T cell modulation of diverse immune pathology. We hypothesize that T cell autoreactivity against apoptotic cell-derived antigens will be associated with pathogenic loss of tolerance or protective regulatory responses during disease.
