PURIFICATION OF OPSONICALLY ACTIVE HUMAN AND RAT COLD-INSOLUBLE GLOBULIN (PLASMA FIBRONECTIN)

Two different affinity chromatographic procedures were developed for the purification of opsonin from plasma or serum, utilizing either heparin or specific antibody containing columns. Activities were measured in liver tissues by the uptake of 125I-labeled latex particles to which gelatin was covalently coupled. Regardless of whether the proteins were derived from human or rat blood, opsonic potencies of the purified products were very similar to that of human cold-insoluble globulin (CIG or fibronectin) obtained as a byproduct in the course of factor XIII fractionation by the method of Lorand & Gotoh [Lorand, L., & Gotoh, T. (1970) Methods Enzymol. 19, 770-782], As judged by electrophoretic and immunological criteria, all procedures yielded materials of similar purity. Furthermore, human and rat opsonins cross-react immunologically. The hepatic system appears to be quite specific for gelatinized particles, because no uptake could be accomplished when fibrinogen, fibrin, or serum albumin was coupled to latex. In competition assays, only gelatin or collagen added in solution caused an inhibition of the uptake of gelatinized particles, while fibrinogen or serum albumin had no effect. In addition to the opsonic protein, some constituent of commercial heparin, other than that responsible for the anticoagulant activity of this mucopolysaccharide mixture, is required for promoting the hepatic uptake of gelatinized latex particles. Further support for the identity of opsonin with CIG, first suggested by Blumenstock and co-workers [Blumenstock, F. A., Saba, T. M., Weber, P., & Loffin, R. (1978) J. Biol. Chem. 253, 4387-4291], was obtained by showing that the opsonic activity of a solution could be reduced considerably by the process of specific cross-linking by factor XIIIa in the presence of fibrin. © 1979, American Chemical Society. All rights reserved.