Immune bactericidal reactions by guinea-pig gamma1 and gamma2 antibodies

Guinea-pigs produced both gamma1 and gamma2 antibodies against Escherichia coli K12, W3110/SM when they were injected intraperitoneally with a suspension of heat-killed bacteria without adjuvant twice a week for 12 weeks. The antibodies were separated by DEAE-cellulose chromatography. The gamma1 antibodies gave PCA reaction against soluble antigens prepared from sonicated E. coli, but the gamma2 antibodies did not. Both gamma1 and gamma2 antibodies induced complement-mediated bactericidal reaction against the homologous bacteria. In the case of gamma1 antibodies presensitization of bacteria with the antibodies before the addition of complement enhanced their bactericidal activity to a degree, EGTA inhibited the bactericidal activity of gamma2 antibodies, more than that of gamma1 antibodies. It is suggested that the gamma1 antibodies kill bacteria via the alternative pathway of complement activation, whilst the gamma2 antibodies exert their bactericidal activity mainly through the classical pathway.