Complement binding is an early feature of necrotic and a rather late eventduring apoptotic cell death

The phagocytosis of dying cells is an integral feature of apoptosis and nec rosis, There are many receptors involved in recognition of dying cells, how ever, the molecular mechanisms of the scavenging process remain elusive. Th e activation by necrotic cells of complement is well established, however, the importance of complement in the scavenging process of apoptotic eel Is was just recently described, Here we report that the complement components C3 and C4 immediately bound to necrotic cells. The binding of complement wa s much higher for lymphocytes compared to granulocytes, In case of apoptoti c cell death complement binding was a rather late event, which in lymphocyt es was preceded by secondary necrosis, Taken together complement binding is an immediate early feature of necrosis and a rather late event during apop totic cell death. We conclude that complement may serve as an opsonin for f ragments of apoptotic cells that have escaped regular scavenging mechanisms .