C5 and Sepsis: A large body of research has demonstrated that C5a/C5aR1 signaling contributes to the pathogenesis of a wide range of inflammatory pathologies, including renal disorders.12, 13, 14 Furthermore, there is compelling evidence from sepsis studies indicating that C5a/C5aR1 signaling can provide counterregulatory effects in host defense through impairment of innate immune cell function and induce excessive inflammatory responses.15