Abstract
The purpose of the present investigation is to be established a more specific method for the determination of a property of insulin binding antibody in human serum and its clinical evaluations. As the principle of this techinque, double antibody precipitation technique using 125I-insulin (porcine) was employed. This method is applicable to only 50 μl of serum of each dilution step (IgG=1: 16, IgA=1: 4, IgM=1: 1, Kappa, Lambda=1: 16) for the determination, and also relatively smaller amount of the second antibody is sufficient to proceed the assay system. Furthermore, it revealed that this method is superior to the other methods (i. e. PEG, gelfiltration, electro phoresis method) in terms of specificity, reproducibility and sensitivity.
The property of insulin binding antibody were observed clinically as followings.
(1) Clases of immunoglobulins: IgG-insulin binding antibodies were detected in 61 patients out of 72 diabetics with insulin treatment and in 3 patients out of 155 hyperthyroidism with thiamazole treatment. However, IgA, IgM-insulin binding antibodies were detected in none of the patients.
(2) Types of light chains of immunoglobulins: Forty-three patients out of 45 diabetics with insulin treatment showed to have both K-and L-type of light chains, but only 2 patients showed K-or L-types. One case of hyperthyroidism with insulin autoimmunity had K-type only.
(3) 125I-insulin binding antibodies showed various affinities to the native human, procine and bovine insulin, respectively. However, sera of 9 patients out of 61 with 125I-insulin binding antibody did not show affinities to various native insulins, but only showed high affinity to the iodinated insulin.
It is suggests that this unique antibody have a high affinity to an altered insulin by means of the iodination.
