Isolation of IgG3 from Polyclonal Human IgG by Affinity Chromatography with Ricinus Agglutinin

Abstract

Ricinus agglutinin purified to homogeneity reacts with serum glycoproteins containing terminal nonreducing galactose residues, including about 10% polyclonal IgG. To study the IgG subclass distribution of this reaction, four monoclonal IgG1 proteins, two IgG2, four IgG3, and two IgG4 proteins were tested by affinity chromatography experiments with insolubilized ricinus agglutinin. Only the IgG3 proteins reacted, and the reactive sites were localized to the Fc fragment. Passage of polyclonal human IgG through a ricinus agglutinin–Sepharose column, followed by elution with lactose, permitted the isolation of IgG3 from normal polyclonal IgG.