The initiating proteases of the complement system: Controlling the cleavage

The complement system is a vital component of the host immune system, but when dysregulated, can also cause disease. The system is activated by three pathways: classical, lectin and alternative. The initiating proteases of the classical and lectin pathways have similar domain structure and employ similar mechanisms of activation. The Clr, Cls and MASP-2 proteases have the most defined roles in the activation of the system. This review focuses on the mechanisms whereby their interaction with substrates and inhibitors is regulated. (c) 2007 Elsevier Masson SAS. All rights reserved.