Differential effectiveness of complement fixed by IgG and IgM antibodies in the cytolysis of dog kidney tissue culture cells.

Sensitizing and complement fixing properties of IgG (7S) and IgM (19S) rabbit anti-horse kidney (Forssman) antibodies have been studied. Agglutination, indirect antiglobulin and mixed antiglobulin techniques were used to determine the extent of antibody sensitization of sheep red cells and dog kidney tissue culture cells. Immune adherence and mixed conglutination were used to demonstrate the presence of sites of complement fixation on these sensitized cells. The relationship between the presence of fixed complement and the subsequent immune lysis of the test cells was examined. Guinea-pig serum-complement appeared to be less well fixed by IgG than by IgM antibodies. However, the complement fixed by IgG antibody was shown to be highly lytic both for sheep red cells and dog kidney tissue culture cells. The fixation of complement by IgM antibodies resulted in weak and relatively ineffective cytolysis of dog kidney cells, but effective haemolysis of sheep red cells. The sensitivity of the immune adherence test for detection of `natural' antibodies was also demonstrated.