Reaction Mechanisms of Nascent C567 (Reactive Lysis)

Abstract

Abstract An activated complex of the fifth and sixth components of complement (C) was generated by treatment of certain human sera with either zymosan or the low molecular weight anticomplementary factor of cobra venom. The interaction of C with C7 and unsensitized erythrocytes was studied. The formation of EC from these reactants was temperature dependent and proceeded most favorably at pH 6.0, ionicity 0.065. The half-life of the hemolytic activity of nascent C was 5 hr at 0°C and less than 2 min at 30°C. When the average numbers of C sites per erythrocyte generated in the presence of optimal C7 were plotted as a function of C input, linear responses were obtained, indicating that a single competent C site is sufficient to prepare the cell for lysis by C8 and C9. Nascent formed by the interaction of C and C7 operates in the absence of antibody and extends the membrane-damaging capacity of the complement system to unsensitized cells.