The role of complement in inflammation and adaptive immunity

Major advances in our understanding of the immunobiology of complement were made within the past 5 years primarily due to the development of gene-targ eting technology. New strains of mice bearing specific deficiencies in seru m complement proteins or their receptors were developed using this approach . Characterization of these mice has provided new and exciting insights int o the biology of the complement system. In this review, we discuss recent r esults on two important aspects of the complement system, i) host protectio n and inflammation, and ii) regulation of B lymphocytes of adaptive immunit y. While these two roles appear distinct, they are linked. We discuss how n atural antibody and classical pathway complement work together in host prot ection against bacterial infection on the one hand bur, on the other, they co-operate to induce inflammation as observed in reperfusion injury. Signif icantly, the lymphocytes that produce natural antibody, the B-1 lymphocytes , are regulated in part by the complement system.