Comparison of the behaviour of IgG and IgM anti-Forssman antibodies in agglutination, haemolysis and cytolysis.

Three anti-Forssman sera, prepared after two, three and six courses of injections with horse kidney antigen, have been fractionated by DEAE-cellulose chromatography. The IgG and IgM antibody activities in the various fractions have been measured by agglutination of untreated and papain treated sheep red cells. They have also been tested by haemolysis of sheep red cells and by immune cytolysis of a continuous line of dog kidney cells. The activity of IgG antibody measured by haemolysis and cytolysis are similar, but the IgM fraction shows much greater activity by haemolysis than by cytolysis. It appears that IgM anti-Forssman antibody is inefficient in lysing nucleated cells with guinea-pig complement.