C5AR1 and Sepsis: Although complement activation and inflammation are essential for the host defence and the healing process following tissue damage and infection, unduly elevated levels of C5a may promote and/or exacerbate pathological conditions underlying various acute and chronic inflammatory disorders such as acute lung injury, ischaemia-reperfusion injuries, sepsis, transplant rejection, rheumatoid arthritis, allergy and asthma9, 11, 12, 13, 14.