Kinetics of the binding of immunoglobulins, antibodies and virus haemagglutination inhibitors to kaolin

Kaolin is widely used in diagnostic virology, mainly to remove serum lipoproteins that may interfere with antibody assaying. The binding kinetics of antibody to kaolin at different pH values and with varying amounts of kaolin indicated a uniform and characteristic binding pattern for IgG with maximum adsorption at pH 5 and no adsorption at pH above 9. To avoid loss of IgG antibody adsorption with kaolin should therefore be performed at pH≥9. The amount adsorbed increased with the amount of kaolin used. The IgM pattern was less uniform with maximum adsorption of total IgM at about 7·0, the amount adsorbed being highly dependent on kaolin concentration. Serum lipoproteins were rapidly and strongly adsorbed independent of pH from 7 to 11 and independent of the lipoprotein content of the serum. The amount of kaolin used was, however, critical.