A Study on cellular requirements for apoptotic cell death of activated T cells in EBV infection

我们使用EB病毒诱导的传染性单核细胞增多症(IM)作为激活T细胞死亡的模型，以阐明病毒感染通过激活诱导T细胞死亡的细胞要求。研究结果如下：1)急性IM患者活化的T细胞和正常人的记忆T细胞均表达CD45RO和Fas抗原，可介导细胞凋亡。与记忆T细胞不同，IM中活化的T细胞在体外简单孵育后容易发生细胞凋亡。通过IM细胞免疫小鼠，我们获得了一种新的小鼠单抗，命名为IMN3.1，它被标记为与易凋亡的T细胞反应。对IMN3.1抗原的分子克隆正在进行中。2)IM中活化的T细胞似乎支持其对凋亡的敏感性，但缺乏具有预防细胞凋亡作用的Bcl2的表达。在寿命较短的粒细胞和单核细胞上可见少量或不表达Bcl2。重要的发现是抗Fas抗体可加速粒细胞和单核细胞的凋亡。这些观察表明，Fas抗原/配体系统可能在解决炎症和免疫反应中发挥关键作用。3)p53癌基因突变被认为是导致人类恶性肿瘤发生的原因。IM患者活化的T细胞虽易发生凋亡，但未见P53的表达。电离辐射可诱导全人群外周血淋巴细胞P53蛋白表达，并伴有明显的细胞凋亡。然而，我们发现淋巴细胞亚群在P53诱导方面存在显著差异。照射后CD_4~+T、CD_8~+T和B细胞中P53的诱生作用显著。相反，TCR-γ/Delta^+T细胞和NK细胞均未显示出可识别的P53水平。这些结果表明，辐射诱导的淋巴细胞凋亡可能是由p53依赖或非依赖的机制介导的。

We employed EBV-induced infectious mononucleosis (IM) as a model of activated T cell death to elucidate cellular requirements for induction of T cell death by activation with viral infection. Obtained results are as follows :1)Both activated T cells in acute IM patients and memory T cells in normal persons express CD45RO and Fas antigen, which can mediate apoptosis. Unlike memory T cells, activated T cells in IM easily undergo apoptotic cell death after on a simple incubation in vitro. By immunizing mice with IM cells, we obtained a novel mouse monoclonal antibody, termed IMN3.1, which was marked to react with apoptosis-prone T cells. Molecular cloning of IMN3.1-identified antigen is in progress.2)Seemingly supporting their susceptibility to apoptosis, activated T cells in IM lacked expression of Bcl-2, which have a preventive function against apoptotic cell death. Low or absent expression of Bcl-2 was observed on granulocytes and monocytes, both of which have shorter life-spans. The important finding was that anti-Fas antibody could accelerated apoptotic cell death in granulocytes and monocytes. These observations suggest that the Fas antigen/ligand system may play a key role in resolution of inflammatory and immune responses.3)The mutation of the p53 oncogene is thought to lead to oncogenosis in human malignancies. Expression of p53 was not found in activated T cells in IM patients, although they were sucseptible to apoptosis. Ionizing irradiation could induce p53 expression on the whole population of peripheral blood lymphocytes, concomitant with marked apoptosis. However, we found a marked difference of lymphocyte subpopulations regarding p53 induction. Induction of p53 in CD4^+ T,CD8^+ T and B cells after irradiation was prominent. In contrast, neither TCR-gamma/delta^+ T cells nor NK cells showed identifiable levels of p53. The results suggest that radiation-induced lymphocytic apoptosis may be mediated by p53-dependent or-independent mechanisms.