特集 生体膜を三重層としてとらえる 補体とそのレセプターを介して誘起される細胞障害と細胞接着

Abstract

Membranes of foreign material are generally highly susceptible to the host complement system, which is a major humoral host defense system. Via the binding of the complement effector, C3, and C9, to the membranes, foreign cells are damaged by a variety of chemical and physical reactions induced by the host immune system. We have found that two membrane proteins classified into short consensus repeat (SCR) protein family, namely CD46 and CD55, are crucial to determine the complement susceptibility of membranes : that is, host cells circumvent autologous complement attack by the expression of either CD46 or CD55, whilst foreign cells are killed by host complement because of their lack of them. In this review, we discuss 1) the molecular mechanism of the membrane deposition of C3 and C9, and the interaction between these effector molecules and inhibitor molecules including CD46 and CD55 (which occur on membranes), 2) the alteration of membrane itself induced by complement attack, 3) the intracellular events (including signal transduction) evoked secondary to complement activation.