Identifying innate immune receptors causing production of proinflammatory cytokine IL-6 by infection of Francisella tularensis 4488

Abstract Description Francisella tularensis (F.t) is a pathogenic species and a causative agent of tularemia. This bacterium is highly infectious and often lethal as F.t causes an overproduction of proinflammatory cytokines. During necroptosis, damage-associated molecular patterns (DAMPs) released from cells bind to the cell surface receptors on macrophages inducing an inflammatory response. Necroptosis activates when RIPK3 phosphorylates the mixed lineage kinase domain-like (MLKL). Toll like-receptors (TLRs) initiate necroptosis mediated by TRAF and RIPK3. The objective of this study is to identify innate immune receptors responsible for the production of proinflammatory cytokines during infection with F.t. The study uses an immortalized C57BL/6 Bone Marrow Macrophage (BMMac) cell line and knockout BMMac that are deficient in various innate immune receptors. The supernatants are collected from these cells and analyzed by ELISA, an enzyme-linked immunosorbent assay, to measure production of inflammatory cytokines. The data from these cells are compared with uninfected and infected C57BL/6 BMMac control cells. Analysis of these mutants reveal the involvement of innate immune receptors, such as IRF3, in triggering the pro-inflammatory cytokine production in response to F.t infection that leads to death of the host. Future direction includes identifying switches in the pathway between apoptosis, necroptosis, and pyroptosis during infection that could clarify receptors’ involvement in cell death. Funding Sources Research reported in this publication was supported by the National Institute Of General Medical Sciences of the National Institutes of Health under Award Number R25GM069621. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Topic Categories Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)