The structure and function of beta TCR on immature thymocytes.

最近的研究表明，betaTCR的表达是CD4^-8^-胸腺细胞向CD4^+8^ -细胞分化的重要步骤，并且betaTCR链在没有其他TCR链的情况下在未成熟的胸腺细胞上表达。为了研究未成熟betaTCR复合物的结构及其在胸腺细胞分化中的作用，我们建立了胸腺淋巴瘤细胞系（lss11 -1）。lb11 -1细胞表面表达较多的atcr，但CD3表达较少。同样在这个细胞系中，betaTCR与alphaatcr没有关联。lls11 -1细胞的α - atcr基因转染物lls11 -1alpha29在细胞表面表达带CD3复合物的α - atcr。最近有研究表明，在B细胞中，在缺乏与CD3相对应的mbl分子的情况下，IgD分子可以在细胞表面表达，并且这些IgD分子与糖基磷脂酰肌醇（GPI）连接。用磷脂酰肌醇特异性磷脂酶C（PI-PLC）处理lls11 -1细胞，降低了lls11 -1细胞上betaTCR的表达，表明betaTCR与gpi相关，尽管PI-PLC处理没有改变lls11 -1alpha29细胞上alphabetaTCR的表达。在转betaTCR的小鼠的CD3^-、betaTCR^+胸腺细胞上也发现了gpi连接的betaTCR的细胞表面表达。而成熟胸腺细胞CD3^<高>,betaTCR^<高>在细胞表面不表达GPI-linked betaTCR，说明未成熟胸腺细胞可以表达GPI-linked betaTCR。虽然用betaTCR抗体或CD3抗体刺激LSB11-1alpha29细胞时，细胞质CA^<2+>有短暂性升高，但用这些抗体刺激LSB11-1细胞时，细胞质CA^<2+>未见升高。目前我们正在研究什么样的信号是通过未成熟的betaTCR复合体转导的。这些结果表明未成熟的betaTCR复合物在未成熟胸腺细胞分化中的作用。

Recently it has been shown that the expression of betaTCR is an important step in the differentiation of CD4^-8^- thymocytes into CD4^+8^+ cells ant that the betaTCR chain is expressed on immature thymocytes in the absence of other TCR chains.In order to study the structure of the immature betaTCR complex and its function in thymocyte differentiation,a thymic lymphoma cell line (LSB11-1)was established.LSB11-1 cells express betaTCR on the cell surface but few CD3.Also in this cell line,betaTCR is not associated with alphaTCR.alphaTCR-gene-transfectant of LSB11-1 cells,LSB11-1alpha29, express alphabetaTCR with CD3 complex on the cell surface.Recently it has been shown that IgD molecules could be expressed on the cell surface in the absence of mbl molecules which correspond to CD3 in B cells,and that those IgD molecules are linked with glycosylphosphatidylinositol(GPI). Treatment of LSB11-1 cells with phosphatidylinositol specific phospholipase C(PI-PLC)reduced the expression of betaTCR on LSB11-1 cells,indicating that the betaTCR is GPI-linked,although the expression of alphabetaTCR on LSB11-1alpha29 cells was not changed by PI-PLC treatment.Cell surface expression of GPI-linked betaTCR was also found on CD3^-,betaTCR^+ thymocytes in betaTCR transgenic mice.However CD3^<high>,betaTCR^<high> mature thymocytes did not express GPI-linked betaTCR on the cell surface,indicating that immature thymocytes can express the GPI-linked betaTCR.Although a transient increase in cytoplasmic CA^<2+> was observed when LSB11-1alpha29 cells were stimulated with betaTCR antibodies or CD3 antibodies,cytoplasmic CA^<2+> increase in LSB11-1 cells was not found when stimulated with those antibodies.Presently we are investigating what kind of signal is transduced via the immature betaTCR complex.These results should show the role of immature betaTCR complex in differentiation of immature thymocytes.