Evidence for the involvement of the Ss protein of the mouse in the hemolytic complement system.

A significant within-strain correlation has been demonstrated between the levels of Ss and hemolytic complement (C) activity in two Ss-high strains. Mouse serum specifically depleted of Ss by absorption with F(ab')2 fragments of anti-Ss had negligible C activity. In control experiments, Ss-specific antigen-antibody complexes formed with F(ab')2 fragments did not fix rabbit C, and bovine serum albumin-specific antigen-antibody complexes formed with F(ab')2 fragments did not fix mouse C. Therefore the removal of C activity by anti-Ss [F(ab')2] was apparently not due to C fixation. These results suggest that the Ss protein is a necessary component of the C system.