DIFFERENCES IN TERMINAL STEPS OF COMPLEMENT LYSIS OF NORMAL AND PAROXYSMAL NOCTURNAL HEMOGLOBINURIA RED-CELLS

Abstract

The number of microscopically visible lesions produced on the membrane for a given degree of lysis by complement was compared in normal and paroxysmal nocturnal hemoglobinuria (PNH) red cells. Ten times as many such lesions were present at a given degree of lysis on normal cells as on PNH cells. Since complement lesions were not formed until C8 [complement protein 8] or C9 was incorporated into the complement sequence, the results suggest that increased lysis of red cells in PNH is due at least in part to more efficient penetration of the PNH membrane by the terminal lytic sequence of complement. Furthermore, the efficiency of the terminal lytic sequence in the lysis of PNH cells when complement was activated by the alternative pathway and the classical pathway was analyzed. There was no significant difference (P < 0.01) in the number of lesions present at an equivalent degree of lysis when initiated by antibody, cobra venom factor or acidification. The efficiency of the terminal lytic sequence apparently does not vary with different modes of activation.