Relationship of the anti-complementary effect of fowl serum to its own haemolytic activity.

Abstract

THE marked, anti-complementary effect of fresh fowl serum on guinea-pig complement and its reduction by heating to 56° C are well known1,2. Treatments of fowl serum by methods other than heating which reduced this effect also resulted in a decrease in its own haemolytic activity3, suggesting that the anti-complementary effect of fowl serum may be related to its own complement content. More recently, it has been shown that the euglobulin fraction of fowl serum, corresponding to the midpiece or first component of fowl complement, is the fraction which reduces the haemolytic titre of guinea-pig complement4,5. This heat-labile euglobulin fraction appears to be the same as the ‘normal chicken factor’ reported to be necessary for the specific fixation of guinea-pig end-piece by fowl antibody/antigen complexes4,6. Its anti-complementary effect on guinea-pig complement was also mentioned, but it was stated that this could be removed by dissolving the fraction in heated normal fowl serum to give a ‘concentrated normal chicken factor’5. Orlans, Rose and Clapp3 investigated this factor and found that, with certain concentrations of fowl serum, it could produce reductions in the haemolytic activity of guinea-pig complement, simulating specific fixation by antigen/antibody mixtures. We have now compared the effects of fowl serum, before and after various treatments, on the haemolytic activities of both fowl and guinea-pig complements.