The Interchangeability of the Complement Components of Different Animal Species

Abstract

Summary: Titrations of the four major complement components in fresh sera from twelve mammalian and two avian species have been made using test reagents prepared from guinea-pig complement. All seven of the mammalian complements evincing hemolytic activity for sheep red-cells sensitized with rabbit hemolysin, were shown to contain all four components. The five mammalian complements without hemolytic effect on this system contained considerable amounts of C′1, variable amounts of C′3, but no demonstrable C′4. Small amounts of C′2 could be detected in three of these five “non-hemolytic” complements when heated guinea-pig serum was added to ensure an adequate excess of the heat-stable components, particularly of C′4. Owing possibly to species incompatibility, the guinea-pig test reagents failed to detect any of the four components in chicken or turkey sera which initially had exhibited some hemolytic activity, a presumable indication of the presence of all four. Studies of the interchangeability of the four components in the complements of the various species showed only those of guinea pig, man, and hamster to be mutually compatible, those of the other species replacing each other partially. The C′1 component of the non-hemolytic complements could be substituted for C′1 of guinea pig and certain of the other hemolytic complements; their C′2 components were not found to be mutually interactive. The role of inhibitory substances in reducing or obscuring the activities of components present in low concentration is considered, as is also the practical importance of differences in the lability of various complements in determining titer values of individual components. Fixation of complement due to interspecies antigen-antibody reactions is suggested as one possible source of anticomplementary effects.