An immunochemical method for the quantitation of insulin antibodies.

A 125I-labelled insulin binding assay is described in which IgG antibody is precipitated by the addition of an optimal concentration of second antibody. Other features include the removal of unlabelled insulin from test sera prior to assay and the use of 22Na as a volume marker. This approach overcomes problems associated with previous assays for insulin antibodies. Clear differences are seen in the IgG insulin binding capacity (IBC) of sera from patients with insulin resistance and injection site lipo-atrophy when compared with insulin-treated diabetics who lack such complications. The precision and flexibility of this technique make it particularly suitable for studies of the immune response to different species and forms of insulin.