The ninth component of guinea-pig complement. Isolation and identification as an alpha 2-globulin

Abstract

A method was described for isolation of the ninth component of guinea-pig complement (C9). Injection of the isolated C9 into rabbits resulted in the production of antisera which contained antibody to a serum protein with an electrophoretic mobility of an α₂-globulin. The identity of C9 with the α₂-globulin was proved by means of immunolysoelectrophoresis and quantitative precipitin reaction. The development of the haemolytic band, observed in the α₂-region by overlaying blood agar containing EAC14235678 after immunoelectrophoresis of guinea-pig serum or purified C9, was completely inhibited by the precipitin line formed with IgG fraction of the antisera. Further, upon incubation of the IgG fraction with varying amounts of guinea-pig serum in the presence of ethylene-diaminetetraacetate, more than 99.5 per cent of C9 activity in serum was precipitated in the antibody excess region and the equivalence zone. It was found only in the antigen excess region and all the other eight components remained unaffected in the supernatant fluids.