Richter W, Eiermann T H, Endl J, Seissler J, Wolfahrt S, Brandt M, Jungfer H, Scherbaum W A
Department of Internal Medicine 1, University of Ulm, Germany.
Diabetologia. 1993 Aug;36(8):785-90. doi: 10.1007/BF00401152.
The first human monoclonal islet cell antibodies of the IgG class (MICA 1-6) obtained from an individual with Type 1 (insulin-dependent) diabetes mellitus were cytoplasmic islet cell antibodies selected by the indirect immunofluorescence test on pancreas sections. Surprisingly, they all recognized the 64 kDa autoantigen glutamate decarboxylase. In this study we investigated which typical features of cytoplasmic islet cell antibodies are represented by these monoclonals. We show by double immunofluorescence testing that MICA 1-6 stain pancreatic beta cells which is in agreement with the beta-cell specific expression of glutamate decarboxylase. In contrast an islet-reactive IgM monoclonal antibody obtained from a pre-diabetic individual stained all islet cells but lacked the tissue specificity of MICA 1-6 and must therefore be considered as a polyreactive IgM-antibody. We further demonstrate that MICA 1-6 revealed typical features of epitope sensitivity to biochemical treatment of the target tissue which has been demonstrated for islet cell antibodies, and which has been used to argue for a lipid rather than a protein nature of target antigens. Our results provide direct evidence that the epitopes recognized by the MICA are destroyed by methanol/chloroform treatment but reveal a high stability to Pronase digestion compared to proinsulin epitopes. Conformational protein epitopes in glutamate decarboxylase therefore show a sensitivity to biochemical treatment of sections such as ganglioside epitopes. MICA 1-6 share typical features of islet cell and 64 kDa antibodies and reveal that glutamate decarboxylase-reactive islet cell antibodies represent a subgroup of islet cell antibodies present in islet cell antibody-positive sera.
从一名1型（胰岛素依赖型）糖尿病患者体内获得的首批IgG类人单克隆胰岛细胞抗体（MICA 1 - 6）是通过对胰腺切片进行间接免疫荧光试验筛选出的细胞质胰岛细胞抗体。令人惊讶的是，它们都识别64 kDa自身抗原谷氨酸脱羧酶。在本研究中，我们调查了这些单克隆抗体所代表的细胞质胰岛细胞抗体的哪些典型特征。我们通过双重免疫荧光测试表明，MICA 1 - 6对胰腺β细胞进行染色，这与谷氨酸脱羧酶的β细胞特异性表达一致。相比之下，从一名糖尿病前期个体获得的一种胰岛反应性IgM单克隆抗体对所有胰岛细胞进行染色，但缺乏MICA 1 - 6的组织特异性，因此必须被视为一种多反应性IgM抗体。我们进一步证明，MICA 1 - 6显示出对靶组织生化处理的表位敏感性的典型特征，这已在胰岛细胞抗体中得到证实，并且已被用于支持靶抗原的脂质而非蛋白质性质的观点。我们的结果提供了直接证据，即MICA识别的表位被甲醇/氯仿处理破坏，但与胰岛素原表位相比，对链霉蛋白酶消化具有高稳定性。因此，谷氨酸脱羧酶中的构象蛋白表位对切片的生化处理表现出敏感性，如神经节苷脂表位。MICA 1 - 6具有胰岛细胞和64 kDa抗体的典型特征，并表明谷氨酸脱羧酶反应性胰岛细胞抗体代表胰岛细胞抗体阳性血清中存在的胰岛细胞抗体亚组。
