Tracking Competent Host Defence to Chronic Inflammation: An In Vivo Model of Peritonitis

Anti-microbial host defence is dependent on the rapid recruitment of inflammatory cells to the site of infection, the elimination of invading pathogens, and the efficient resolution of inflammation so as to minimise damage to the host. The peritoneal cavity provides an easily accessible and physiologically relevant system where the delicate balance of these processes may be studied. Here, we describe murine models of peritoneal inflammation that enable studies of both competent anti-microbial immunity and inflammation associated tissue damage as a consequence of recurrent bacterial challenge. The inflammatory hallmarks of these models reflect the clinical and molecular features of peritonitis episodes seen in renal failure patients on peritoneal dialysis. Development of these models relies on the preparation of a cell-free supernatant derived from an isolate of Staphylococcus epidermidis (termed SES). Intraperitoneal administration of SES induces a TLR2-driven acute inflammatory response that is characterised by an initial transient influx of neutrophils that are replaced by a more sustained recruitment of mononuclear cells and lymphocytes. Adaptation of this model using a repeated administration of SES allows investigations into the development of adaptive immunity and memory responses, and the hallmarks associated with tissue remodelling and fibrosis. These models are therefore clinically relevant and provide exciting opportunities to study both innate and adaptive immune responses in the control of bacterial infection and pathogenesis.