Analysis of autoantibodies in the mechanism of the occurrence of multiple autoimmune endocrinopathies

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We have established an assay method of antipituitary antibodies (APA) as a screening test, using enzyme-linked immunosorbent assay (ELISA) and evaluated on its clinical usefulness. The soluble fractions of rat pituitary cells were used as antigens of ELISA/APA.The assay, similar to that utilized indirect enzyme autoantibodies, was performed. The results by this assay method were calculated as the cut off index (C.I value), using colorimetric reaction and absorvance at 450 nm.Pathiens with autoimmune thyroid diseases (Hashimoto's thyroiditis Graves, disease) showed approximately 20% positive for ELISA/APA.On the other hand, 34% in Hashimoto's thyroiditis and 28% in Graves disease had a positive band by Western blot analysis, which was identical with 22 kDa protein. Furthermore, 39% in patients with insulin-dependent diabetes mellitus (IDDM) was positive for ELISA/APA,in which 64% in such patients was positive by Western blot analysis.We next analyzed 22 kDa protein ontained by Western blot method, which was one of matched antigens to APA.The analysis of amino acid sequence in this protein resulted in P-A-M-L-S-S-L-F-N-A-V-L-R from the N terminal side. Employing homology analysis, this matched antigens was found to be identical with molecular weight of somatotropin.Further studies are needed to determine the nature of other positive bands by Western blot analysis. As reported previously, some patients with pituitary dwarfism and panhypopituitarism showed positive APA.On the basis of these observations, the present study suggests that measurements of APA are a useful indicator of multiple autoimmune endocrinopathies.