Evidence that rabbit gamma G haemolysin in capable of utilizing guinea-pig complement more efficiently than rabbit gamma M haemolysin.

Sheep erythrocytes sensitized with rabbit γG anti-Forssman haemolysin may be haemolysed more efficiently and to a greater extent by limited amounts of guinea-pig complement components than are cells sensitized with γM anti-Forssman haemolysin. This apparent difference, noted in all components titrations, was two-fold or greater in titrations of C2 and components following C2 in the haemolytic sequence. Neither site to site transfer of C2 nor AC142 could account for the 100 per cent greater haemolytic efficiency of C2 in haemolytic assays. These results indicate that immunoglobulin class plays a more complex role in immune haemolysis than simple initiation of complement fixation and suggest that γG complement fixing sites may be more efficient than γM sites in producing biological damage.