Evaluation of the bactericidal effect of the membrane attack complex of serum complement

: The bactericidal activity of serum complement and particularly of the membrane attack complex (MAC-C5b-C9) was studied on E. coli C600 with a simple functional test. The test evaluates the in vitro kinetics of the bactericidal effect and the subsequent counting of surviving germs. Homozygous deficiency of a particular membrane attack complex protein was easily detected from a total loss of bactericidal activity. These results were confirmed on Neisseriae meningitidis A and C, but in this case a more complex protocol was required. Deficits of proteins of the membrane attack complex sequence of complement are often found in sera of patients suffering from recurrent Neisseriae infections. This simple test, adapted to family studies, appears, thus, as a valuable basis for a detection of relatives at risk.