Crisá L, Sarkar P, Waite D J, Friedrich F H, Rajan T V, Mordes J P, Handler E S, Thiele H G, Rossini A A
Diabetes Division, University of Massachusetts, Worcester Medical Center 01605.
Diabetes. 1993 May;42(5):688-95. doi: 10.2337/diab.42.5.688.
T-cells expressing the RT6 surface alloantigen appear to perform important immunoregulatory functions in the rat. Diabetes-prone BB rats lack circulating RT6+ T-cells and spontaneously develop autoimmune diabetes mellitus and thyroiditis. The coisogenic diabetes-resistant BB rat does circulate RT6+ T-cells and is free of disease. Transfusions leading to engraftment of RT6+ T-cells prevent both diabetes and thyroiditis in the diabetes-prone rat. To investigate the absence of this subset in the lymphopenic BB rat, we used both molecular and biochemical procedures and made the following observations: 1) an mRNA encoding RT6 protein is present in diabetes-prone spleen cells; 2) nucleotide sequencing of this transcript reveals an intact coding sequence for the RT6.1 alloantigen; 3) sensitive chemiluminescent assay of diabetes-prone lymph node cell detergent extracts shows that diabetes-prone RT6 mRNA is translated in vivo; 4) quantitatively, diabetes-prone lymph node cells express < or = 10% of the RT6.1 protein found on similar numbers of diabetes-resistant BB cells; and 5) finally, we obtained evidence of an intact phosphatidylinositol linkage of the molecule to the cell surface and successfully immunoprecipitated the phosphatidylinositol-linked protein with DS4.23 monoclonal antibody, indicating that the RT6.1 antigen is correctly processed and folded in diabetes-prone lymph node cells. We conclude that the near total absence of RT6+ T-cells in the diabetes-prone BB rat is unlikely to be because of a defect in RT6 gene expression per se. Defects in RT6 gene regulation or other cellular defects leading to premature cell death in the T-cell lineage, alone or in combination, may instead be responsible.
表达RT6表面同种异体抗原的T细胞似乎在大鼠中发挥重要的免疫调节功能。易患糖尿病的BB大鼠缺乏循环中的RT6⁺ T细胞，并自发发展为自身免疫性糖尿病和甲状腺炎。同基因抗糖尿病BB大鼠确实有循环中的RT6⁺ T细胞，且无疾病。导致RT6⁺ T细胞植入的输血可预防易患糖尿病大鼠的糖尿病和甲状腺炎。为了研究淋巴细胞减少的BB大鼠中该亚群的缺失情况，我们使用了分子和生化方法，并得出以下观察结果：1）编码RT6蛋白的mRNA存在于易患糖尿病的脾细胞中；2）该转录本的核苷酸测序揭示了RT6.1同种异体抗原的完整编码序列；3）对易患糖尿病的淋巴结细胞去污剂提取物进行灵敏的化学发光分析表明，易患糖尿病的RT6 mRNA在体内被翻译；4）定量分析显示，易患糖尿病的淋巴结细胞表达的RT6.1蛋白占相同数量抗糖尿病BB细胞上发现的RT6.1蛋白的≤10%；5）最后，我们获得了该分子与细胞表面完整磷脂酰肌醇连接的证据，并用DS4.23单克隆抗体成功免疫沉淀了磷脂酰肌醇连接蛋白，表明RT6.1抗原在易患糖尿病的淋巴结细胞中被正确加工和折叠。我们得出结论，易患糖尿病的BB大鼠中RT6⁺ T细胞几乎完全缺失不太可能是由于RT6基因表达本身存在缺陷。相反，RT6基因调控缺陷或其他导致T细胞谱系中细胞过早死亡的细胞缺陷，单独或共同作用，可能是原因所在。
