Inhibition of the Eighth Component of Complement (C8) by Ethylenediaminetetra-Acetate (Edta)

Abstract

Functionally pure C8 from human or guinea pig serum was inactivated by 1 to 2 × 10-3 M EDTA. Native C8 in serum was partially inactivated by EDTA, but much longer periods of incubation at 37°C were required for this to be evident. The effect of EDTA on C8 was dependent upon time, temperature, and concentrations of both the chelating agent and C8. The inactivation of C8 by EDTA was partially or totally reversed by the addition of Ca2+ or by dialysis, but reversal was dependent upon the duration of exposure and the temperature. The process became irreversible within relatively short periods of time at 30°C and 37°C. EDTA had no apparent effect on the activity of cell-bound C8 or on the binding site of C8 for C9, but it did impair the binding site of C8 for C7. Neither EAC1–7 nor C9 was affected by EDTA.