Granja C B, Gozashti C S, Dasgupta J D
Department of Pathology, Harvard Medical School, Dana-Farber Cancer Institute, Boston, Massachusetts.
Immunology. 1994 Nov;83(3):414-9.
The membrane-bound CD4 glycoprotein has been proposed to act like a co-receptor along with the T-cell antigen receptor (TCR/CD3) during ligand recognition and cell activation. Due to its association with the protein tyrosine kinase (PTK) p56lck, CD4 is believed to transduce a signal and support CD3 activation of T cells. In this study we have shown that CD3 ligation on murine T-cell hybridomas induces tyrosine phosphorylation of proteins, including phospholipase C-gamma 1 (PLC gamma 1), both in the presence as well as in the absence of CD4-linked p56lck. Furthermore, using HPB clones deficient in CD3/PTK association, it has been found that the presence of CD4/p56lck does not overcome the defect in signalling. Not even co-aggregation of CD4 with CD3 triggers tyrosine phosphorylation of proteins in these cells. Together, the present results indicate that CD3-linked PTK(s) plays a primary role in the induction of signalling through TCR/CD3, and the presence of CD4/p56lck is neither necessary nor sufficient to elicit these events. In the light of these results a possible role for CD4 in antigen presentation has been proposed.
有人提出，膜结合型CD4糖蛋白在配体识别和细胞激活过程中可作为共受体与T细胞抗原受体（TCR/CD3）协同发挥作用。由于CD4与蛋白酪氨酸激酶（PTK）p56lck相关联，因此人们认为CD4可转导信号并支持T细胞的CD3激活。在本研究中，我们发现，在存在和不存在与CD4相连的p56lck的情况下，鼠T细胞杂交瘤上的CD3连接均可诱导包括磷脂酶C-γ1（PLCγ1）在内的蛋白质发生酪氨酸磷酸化。此外，使用缺乏CD3/PTK关联的HPB克隆发现，CD4/p56lck的存在并不能克服信号传导缺陷。即使CD4与CD3共聚集也不会引发这些细胞中蛋白质的酪氨酸磷酸化。总之，目前的结果表明，与CD3相连的PTK在通过TCR/CD3诱导信号传导中起主要作用，而CD4/p56lck的存在对于引发这些事件既非必要条件也非充分条件。鉴于这些结果，有人提出了CD4在抗原呈递中的可能作用。
