Interactions between Ricinus Agglutinin and Human Plasma Proteins

Abstract

Ricinus agglutinin purified to homogeneity precipitates certain serum glyco‐proteins containing terminal non‐reducing galactose residues. Immunoelec‐trophoresis of human sera in agarose gel with ricinus agglutinin in the antibody trough gave 2 fusing precipitin lines due to reaction with IgM and haptoglobin. All of 50 monoclonal IgM proteins precipitated with ricinus agglutinin, and the reactive sites were localized to the Fc μ fragment. By affinity chromatography on Sepharose columns containing insolubilized ricinus agglutinin prealbumin, albumin, α1‐lipoprotein, α1‐antitrypsin, α1‐acid glycoprotein, α1‐antichymotrypsin, α2HS glycoprotein, Ge‐globulin, caerulo‐plasmin, β‐lipoprotein, β1 C‐globulin, and transferrin were not retained, whereas α2‐macroglobulin, haptoglobin, IgM, IgA, and IgG were retained and could be eluted with lactose. Fused rocket immunoelectrophoresis revealed varying degrees of microheterogeneity among the latter proteins; almost all of IgM but only a small fraction of polyclonal IgG was retained on the ricinus column.