C5 and Sepsis: Blockade of C5a or the C5a receptor has markedly improved morbidity and mortality in rodent models of cecal ligation and puncture, leading to severe poly-microbial sepsis [106] C1-inhibitor has been used in patients with sepsis and other systemic inflammatory reactions associated with capillary leakage, but randomized clinical studies using complement inhibitors in sepsis have not been performed.