Activation of complement by antibodies to the keratosulphate-like host antigen of Sendai virus

Sendai virus is haemolytic against erythrocytes from different species. Pre-treatment of Sendai virus with antibody and complement (C) enhances the haemolytic activity of the virus. This property was used to examine the pathway by which C is activated by Sendai virus antigen-antibody complexes. Antibody against the keratosulphate-like host antigen was used in a monospecific antigen-antibody system. Evidence is presented that both the classical and the alternative pathway is activated; the alternative to a much lower extent.