Cutrona G, Leanza N, Ulivi M, Majolini M B, Taborelli G, Zupo S, Baldari C T, Roncella S, Ferrarini M
Istituto Nazionale per la Ricerca sul Cancro, IST-Servizio di Immunologia Clinica, Genoa, 16132, Italy.
Cell Immunol. 1999 Apr 10;193(1):80-9. doi: 10.1006/cimm.1999.1455.
Using immunofluorescence, RT-PCR, and Western blotting, we have demonstrated the ability of human B cells to express CD4. In each of the 10 lymphoblastoid cell lines (LCL) tested there was variable, but definite, proportion of CD4-positive B cells. Expression of CD4 was related to the cell cycle; CD4 was expressed in the G1 phase and continued at later phases of the cell cycle. CD4 was in part internalized and degraded by the LCL B cells. Surface CD4 was associated to lck and its crosslinking resulted in tyrosine phosphorylation. Additional experiments conducted on freshly prepared tonsillar B cells demonstrated that CD4 was expressed by large activated B cells, but not by small resting B cells. However, not all the activated tonsillar B cells had surface CD4 since germinal center cells were CD4-negative. Crosslinking of CD4 on LCL or on tonsillar activated B cells resulted in apoptosis in vitro, a finding that indicates the capacity of CD4 to deliver functional signals to B cells and to play a regulatory function in their physiology. Exposure of CD4 expressing B cells to gp120 under conditions that resulted in CD4 crosslinking also caused apoptosis suggesting some implications for the pathophysiology of AIDS.
通过免疫荧光、逆转录聚合酶链反应（RT-PCR）和蛋白质免疫印迹法，我们已经证明人类B细胞具有表达CD4的能力。在所检测的10个淋巴母细胞系（LCL）中，每个系都有比例不等但确定的CD4阳性B细胞。CD4的表达与细胞周期有关；CD4在G1期表达，并在细胞周期的后期持续表达。CD4部分被LCL B细胞内化并降解。表面CD4与lck相关联，其交联导致酪氨酸磷酸化。对新鲜制备的扁桃体B细胞进行的额外实验表明，大型活化B细胞表达CD4，而小型静止B细胞不表达。然而，并非所有活化的扁桃体B细胞都有表面CD4，因为生发中心细胞是CD4阴性的。LCL或扁桃体活化B细胞上的CD4交联在体外导致细胞凋亡，这一发现表明CD4有能力向B细胞传递功能性信号并在其生理过程中发挥调节功能。在导致CD4交联的条件下，将表达CD4的B细胞暴露于gp120也会导致细胞凋亡，这对艾滋病的病理生理学有一些启示。
