Role of complement in in vitro and in vivo lung inflammatory reactions.

Complement is one of the integral buttresses of the inflammatory response. In addition to host defense activities, proinflammatory properties of several complement components are described. This overview elucidates the role of complement in inflammatory reactions in vitro and in vivo, focusing on the complement activation products, C5a, and the membrane attack complex, C5b-9. Using several approaches, the impact of these complement components in mechanisms relevant to neutrophil recruitment is emphasized. In addition, the participation of complement in endothelial superoxide generation and its essential requirement for full expression of lung injury is demonstrated, as are the involved intracellular signal transduction pathways. Understanding the mechanisms of complement-induced proinflammatory effects may provide a basis for future therapeutic blockade of complement and/or its activation products.