Precipitin Reactions of Clq with Various γ Globulins and Anionic Macromolecules

Abstract

Recently a gel diffusion method has been established for demonstrating C1q precipitin reactions with aggregates or complexes of γ globulin. In this system the marked affinity of aggregated γG3 for C1q is very evident when compared to the reactions of γG1 and γG2 aggregates and is consistent with the known affinity of the monomeric proteins for C1q: γG3 > γG1 > γG2. In contrast, however, to the affinity studies with monomeric γG4 which show no combination of this protein with C1q, aggregates of some γG4 globulin do precipitate with C1q in gel diffusion. These aggregates are unusual in that they are not anticomplementary. This situation is not unique since certain anionic substances such as DNA precipitate strongly with C1q in gel diffusion but do not have a commensurate anticomplementarity in vitro or in vivo. C1q precipitin reactions in gel diffusion have been found useful in detecting γ globulin complexes in pathologic fluids in certain immune complex diseases.