[Studies of the possible importance of complement in increasing the hemagglutination-inhibiting activity of rabbit IgM against Sendai virus].

An investigation has been carried out in order to ascertain the effect of the presence of complement on the HI antibodies of the IgM class obtained in rabbit against Sendai virus. Contrary to the results obtained by some AA. with other viruses, in this case the presence of complement in the form of fresh guinea-pig serum has not modified the HI titre. It has however been demonstrated that in the guinea-pig serum an inhibitor is present, which is active towards Sendai virus and can be identified as a 19S alpha-globulin.