Anion exchange chromatographic distribution of human monoclonal immunoglobulin G is determined by heavy chain subclass and level of sialic acid expression

Anion exchange chromatography is a widely accepted method for purification of immunoglobulins. In this work, we used human monoclonal immunoglobulin G (IgG) with structure and solubility of normal human IgG as a model for studying chromatographic behavior of particular molecular forms of IgG. Human sera with monoclonal IgG were fractionated on a strong anion exchanger, Q Sepharose Fast Flow. With 20 mM Tris pH 7.5 as a start buffer, 42% of human monoclonal IgG passed through column, and 58% of them remained adsorbed. Bound monoclonal IgG were eluted from the exchanger by linear increasing of concentration of NaCl from 0 to 0.5 M. The chromatographic distribution of human monoclonal IgG correlated with their electrophoretic mobilities in agarose gels, and it was dependent on γ heavy chain isotype. Light chain type, as well as serum concentration of monoclonal IgG did not influence their chromatographic behavior. The level of heavy chain sialic acid expression, but not of galactose and N-acetylglucosamine, significantly determined chromatographic distribution of serum monoclonal IgG. In addition to the information on the chromatographic behavior of human monoclonal IgG, we believe that the presented data could provide useful information about the possible use of Q Sepharose Fast Flow matrix for the isolation of specific molecular forms of human IgG.