Mechanism of complement-induced cell lysis. Demonstration of a three-step mechanism of EAC1-8 cell lysis by C9 and of a non-osmotic swelling of erythrocytes.

Sheep erythrocytes were sized by an electrical method during lysis by antibody and complement. No volume changes were observed upon to the EAC1-8 cell intermediate. Three steps could be distinguished in the reaction of C9 with EAC1-8 cells: fixation of C9 to EAC1-8 cells, a process which proceeds also at 0 degrees C; temperature-dependent swelling of the EAC1-9 cells; and lysis of the cells. We could show that swelling of the erythrocytes induced by the complement reaction is independent of protein osmotic forces and is caused by an alteration of the erythrocyte membrane.