Maecker H T, Levy R
Stanford University Medical School, CA 94305.
J Immunol. 1988 Nov 1;141(9):2994-3002.
We have sought to address the question of clonal variation of TCR within a human T leukemia cell line, HPB-ALL. To do so, a panel of anti-idiotypic antibodies was produced and the cell line examined for variants. We isolated both spontaneous idiotype and receptor-negative variants without applying mutagens or any selective pressure other than sorting the cells. These sorted and cloned populations are all clonally related to each other as shown by their beta-TCR locus gene rearrangements. The idiotype variants have alpha-chains which are differentially glycosylated, but they have the same size core protein after treatment with peptide N-glycosidase F to remove their carbohydrate side chains. This probably accounts for their idiotypic difference, since the antibody that distinguishes them appears dependent upon glycosylation for its binding, as shown by immunoprecipitation in the presence versus the absence of tunicamycin, which inhibits glycosylation from occurring. The idiotype variants differed from one another in variable region sequences by only a single amino acid substitution in the beta-chain, which is likely not important for the idiotypic difference. The receptor-negative variant produces both alpha- and beta-mRNA and cytoplasmic protein for TCR, but fails to transport this protein to the cell surface. We conclude that idiotype and receptor-negative variants of a T cell clone can occur in the absence of appreciable somatic mutation.
我们试图解决人类T白血病细胞系HPB - ALL中TCR的克隆变异问题。为此，制备了一组抗独特型抗体，并对该细胞系进行变异检测。我们分离出了自发独特型变异体和受体阴性变异体，未施加诱变剂或任何选择性压力，只是对细胞进行了分选。如β - TCR基因座基因重排所示，这些分选并克隆的群体彼此均为克隆相关。独特型变异体的α链存在差异糖基化现象，但在用肽N - 糖苷酶F去除其碳水化合物侧链后，它们具有相同大小的核心蛋白。这可能解释了它们的独特型差异，因为区分它们的抗体的结合似乎依赖于糖基化，在存在与不存在衣霉素（抑制糖基化发生）的情况下进行免疫沉淀实验可证明这一点。独特型变异体在可变区序列上彼此仅在β链中有一个氨基酸替换的差异，这可能对独特型差异并不重要。受体阴性变异体可产生TCR的α和β mRNA以及细胞质蛋白，但无法将该蛋白转运至细胞表面。我们得出结论，T细胞克隆的独特型和受体阴性变异体可在无明显体细胞突变的情况下发生。
