Clinical significance of auto natural anti-insulin antibodies in normal cats

研究表明，猫血清中存在天然的抗胰岛素自身抗体，这些抗体就是免疫球蛋白。为了阐明抗胰岛素免疫球蛋白的意义，我们建立了检测猫血清中免疫球蛋白的夹心ELISA法。该酶联免疫吸附试验的准确性足以确定胰岛素结合的免疫球蛋白浓度。用该方法测定了130只家猫和11只猫科动物(狮子、豹、雪豹、山猫和山猫)的血浆抗胰岛素免疫球蛋白浓度。所有受试者的抗胰岛素免疫球蛋白检测范围为80~4884μg/ml。瘦肉猫的抗胰岛素免疫球蛋白浓度较高，且与总免疫球蛋白浓度呈正相关，但与血糖和胰岛素浓度无相关性。糖尿病猫的血浆抗胰岛素免疫球蛋白浓度略高，但在正常猫的范围内。初生幼猫脐血中未检测到抗胰岛素免疫球蛋白，哺乳后升高。这些母体抗体在哺乳期间逐渐下降，并在断奶时逆转下降的趋势。利用牛胰岛素的部分多肽进行表位定位。抗原识别部分为胰岛素分子A、B链的亲水末端。用高效液相色谱法将血清中的抗胰岛素免疫球蛋白分为4个组分。利用一个峰最高的组分，我们在猫的脂肪细胞中检测到一种磷酸化的酪氨酸蛋白。加入免疫球蛋白结合的胰岛素后，其磷酸化程度比游离胰岛素强，提示抗胰岛素免疫球蛋白可能增强了胰岛素的作用。

It has been revealed that there have been anti-insulin natural auto anti-insulin antibodies in serum of cats, and those were the IgG. To clarify the significance of anti-insulin IgGs, we developed a sandwich ELISA for determination of the IgGs in serum of cats. The accuracy of the ELISA was sufficient for determination of insulin-bound IgG concentrations. By used of this ELISA, we determined plasma anti-insulin IgG concentrations in 130 domestic cats and 11 other felidae(lions, leopards, snow leopards, bobcats and lynx). Anti-insulin IgGs were detected in ranges from 80 to 4, 884μg/ml in all individuals. Anti-insulin IgG concentrations were high in lean cats, and correlated positively with total IgG concentrations, but not with plasma glucose and insulin concentrations. In cats with diabetes mellitus, plasma anti-insulin IgG concentrations were slightly high, but within the range of normal cats. Anti-insulin IgGs were not detected in cord blood of newborn kittens, and increased after suckling. These maternal antibodies decreased gradually during suckling period, and reversed the falling trend at weaning.Anti-insulin IgGs were fractionated by affinity chromatography with a column fixed bovine insulin. Epitope mapping was carried out by use of partial peptides of bovine insulin. The antigen-recognition parts were extrapolated hydrophilic terminals of A and B chains of insulin molecule.Serum anti-insulin IgGs were divided into 4 fractions by high performance liquid chromatography. By use of a fraction with highest peak, we detected a phosphorylated tyrosine proteins in cultured adipocytes derived from the cat. The phospholylation was stronger after addition of the IgG-binding insulin than free insulin, suggesting that the anti-insulin IgG might enhance the action of insulin.