Anticomplementary properties of plasmin-treated human G immunoglobulin and its components

Plasmin-treated human gamma-globulin, isolated plasmin residual portion (PRG), Fab and Fc fragments were tested for anticomplementary properties. The plasmin digest had very low anticomplementary activity while some of its components were anticomplementary, the latter probably due to alterations resulting from the isolation procedures employed. The highest activity was found in the isolated Fc fragment, no activity being detected in the isolated Fab fragment. Various mixtures of the isolated components were also tested, the results indicating that the increase in anticomplementary activity of the PRG and the Fc fragment was markedly lower when the Fab fragment was present.