Method for rapid quantitation and characterization of insulin antibodies.

Abstract

Nearly all insulin-treated diabetic patients develop antibodies to insulin. The clinical importance of these antibodies is not exactly known regarding their general influence on the therapeutic control of the diabetic and the development of secondary complications. There is no doubt, however, about the role of the antibody titer in some forms of insulin resistance. Besides cases of hypoglycemia caused by insulin injections and the rare forms of diabetes caused by autoimmune insulin antibodies, insulin resistance is the main indication for measuring insulin antibodies. On the other hand, measurement of free and bound insulin in insulin-treated patients and the characterization of the antibodies is of broad scientific interest. The classical serological methods such as immunoprecipitation, complement binding, agglutination, and hemagglutination have proved not to be applicable to the insulin antibody, or too insensitive (see e.g., 1). The introduction of radiolabeled insulin by Kallee (2) made possible direct determination of antibody-bound insulin. In recent years several such methods have been described. Free and antibody-bound insulin are separated by either electrophoresis on various supporting materials (3-9); ultracentrifugation (1, 10, 11); adsorption by dextran-charcoal (12, 13), ion-exchange resin (14), or cellulose (15); gel filtration (16); or by precipitation methods (17-20). In some of these methods the equilibrium between free and antibody bound insulin is influenced during the procedure; moreover, most of them are too laborious for routine use. In 1971, Desbuquois and Aurbach (21) described how free and antibody-bound peptide hormones could be separated by use of polyethylene glycol (PEG). In the following we describe a method involving PEG for rapidly measuring and characterizing insulin antibodies.