Determination of insulin specific IgE in serum of diabetic patients by solid-phase radioimmunoassay.

A solid-phase assay system for quantitative measurement of insulin specific IgE has been developed. Insulin specific IgE and IgG are bound to insulin covalently coupled to Sepharose particles. After a washing procedure which removes unbound immunoglobulins, 125I-anti-human IgE-rabbit globulin is added to the Sepharose to determine the amount of bound IgE. The use of standardized 125I-anti-human-IgE-globulin permits quantitation against a calibration curve of IgE and expression as units/ml. No cross-reactivity of IgG was found. Insulin specific IgE was determined in the sera of diabetic patients. Patients treated with porcine or mixed species purified insulin (monocomponent MC) did not differ significantly from a non-diabetic control group, whereas serum samples taken from patients treated with crystallized insulin preparations showed a significantly higher level of insulin specific IgE (p less than 0.05). Twenty-four patients with generalized insulin allergy and eight patients with immunological insulin resistance also had considerably higher values of IgE antibodies than the control group (p less than 0.001 and p less than 0.005, respectively). No correlation was found between the concentration of insulin specific IgE and IgG in individual sera and the level of insulin specific IgE was independent of the total IgE. In all cases of allergy elicited by purified insulin (monocomponent MC), it was ascertained that the diabetic patients in question had received less pure insulin during earlier treatment.