Studies of Guinea Pig Complement Component C9: Reaction Kinetics and Evidence that Lysis of EAC1–8 Results from a Single Membrane Lesion Caused by One Molecule of C9

摘要

The generation of EAC1–9 from EAC1–8 by reaction with C9 proceeds without time lag and the initial reaction velocity is directly proportional to the concentrations of C9 and EAC1–8. These characteristics, as well as the low temperature sensitivity, indicate that the reaction is not enzymatic. The subsequent lysis of EAC1–9 is highly sensitive to temperature, the Q10 being approximately 2. Rabbit anti-guinea pig C9 blocks the reaction of C9 with EAC1–8, but does not interfere with lysis of EAC1–9. Input of 1 to 2 molecules of C9 suffices for lysis of 1 EAC1–8. The rate of lysis of EAC1–9 is proportional to the concentration of C9 per cell. The dose-response curve in the titration of C9 follows a monotonic course concave to the abscissa representing the concentration of C9. It is concluded from these results that lysis of EAC1–8 results from a single membrane lesion caused by 1 molecule of C9.