Recognition of thyroid autoantigen by T cell clones derived from autoimmune thyroiditis lesions ; Analysis of epitope in thyroglobulin

利用4种来源于小鼠自身免疫性甲状腺炎病变的CD4~+T细胞克隆，分析了在诱发自身免疫性甲状腺炎过程中起关键作用的甲状腺球蛋白抗原决定簇(表位)。F1唯一MHC(H-2；b/k&gt；)限制性T细胞克隆N5P-0E14(TCRVbeta8.3)对小鼠TG有反应，而对牛和人TG无反应。I-A^b限制性N5P-0E15(Vbeta2)能识别小鼠和人TG，但不能识别人TG。而I-A^k限制性、N5P-3B2(Vbeta14)和N6G-4B1(Vbeta未知)对所有小鼠、牛和人的TG均有反应。这些结果表明，TG分子中至少存在3个T细胞识别的表位。其次，分析了人TG的3个合成肽：激素性酪氨酸、TA(HTg1-11)、TB(HTg2546-2571)和TC(HTg2738-2748)。TA和TB的氨基酸序列在人、牛和大鼠TG中高度保守。而TC与大鼠TG的同源性相对较低。此外，TB含有氨基酸序列(D-Y-A-S)，与Rothbard算法一致。这3种合成肽和TB-I(碘化TB)均不能被4种类型的CD4~+T细胞克隆识别。换句话说，自身免疫性甲状腺炎诱导的CD4^+T细胞克隆不识别甘油三酯的激素生成部分。进一步的分析将需要使用由cDNA合成的大肽来确定T细胞的TG表位。

We analyzed the antigenic determinants (epitopes) of thyroglobulin (Tg) critical for the induction of autoimmune thyroiditis by using 4 types of CD4^+T cell clones derived from autoimmune thyroiditis lesions in mice. F1 unique MHC (H-2^<b/k>) restricted T cell clone, N5P-0E14 (TCRVbeta8.3) responded to mouse Tg but not to bovine and human Tg. I-A^b restricted, N5P-0E15 (Vbeta2) recognized mouse and boving Tg but not human Tg. On the other hand, I-A^k restricted, N5P-3B2 (Vbeta14) and N6G-4B1 (Vbetaunknown) could respond to all of mouse, bovine and human Tg. These results seggest that at least 3 epitopes recognized by T cells should exist in Tg molecule. Next, 3 synthetic peptides of human Tg including hormonogenic tyrosine ; TA (HTg1-11) , TB (HTg2546-2571) and TC (HTg2738-2748) , were analyzed. Amino acid sequence of TA and TB were considered highly conserved among human, boving and rat Tg. In contrast, homology of TC to rat Tg was relatively low. In addition, TB contained amino acid sequence (D-Y-A-S) which is compatible to Rothbard's algorithm. None of these 3 synthetic peptides and TB-I (iodinated TB) could not be recognized by 4 types of CD4^+T cell clones. In other words, autoimmune thyroiditis inducing CD4^+T cell clones did not recognize hormonogenic portion of Tg. Further analysis using large peptide synthesized by cDNA will be required to identify epitopes of Tg for T cells.