Pettersen R D, Hestdal K, Olafsen M K, Lie S O, Lindberg F P
Department of Pediatric Research, The National Hospital, Oslo, Norway.
J Immunol. 1999 Jun 15;162(12):7031-40.
Activation-induced death of T cells regulates immune responses and is considered to involve apoptosis induced by ligation of Fas and TNF receptors. The role of other receptors in signaling T cell death is less clear. In this study we demonstrate that activation of specific epitopes on the Ig variable domain of CD47 rapidly induces apoptosis of T cells. A new mAb, Ad22, to this site induces apoptosis of Jurkat cells and CD3epsilon-stimulated PBMC, as determined by morphological changes, phosphatidylserine exposure on the cell surface, uptake of propidium iodide, and true counts by flow cytometry. In contrast, apoptosis was not observed following culture with anti-CD47 mAbs 2D3 or B6H12 directed to a distant or closely adjacent region, respectively. CD47-mediated cell death was independent of CD3, CD4, CD45, or p56lck involvement as demonstrated by studies with variant Jurkat cell lines deficient in these signaling pathways. However, coligation of CD3epsilon and CD47 enhanced phosphatidylserine externalization on Jurkat cells with functional CD3. Furthermore, normal T cells required preactivation to respond with CD47-induced apoptosis. CD47-mediated cell death appeared to proceed independent of Fas or TNF receptor signaling and did not involve characteristic DNA fragmentation or requirement for IL-1beta-converting enzyme-like proteases or CPP32. Taken together, our data demonstrate that under appropriate conditions, CD47 activation results in very rapid T cell death, apparently mediated by a novel apoptotic pathway. Thus, CD47 may be critically involved in controlling the fate of activated T cells.
T细胞的激活诱导性死亡调节免疫反应，被认为涉及Fas和TNF受体连接诱导的细胞凋亡。其他受体在T细胞死亡信号传导中的作用尚不清楚。在本研究中，我们证明CD47免疫球蛋白可变结构域上特定表位的激活可迅速诱导T细胞凋亡。针对该位点的一种新单克隆抗体Ad22可诱导Jurkat细胞和CD3ε刺激的外周血单个核细胞（PBMC）凋亡，这通过形态学变化、细胞表面磷脂酰丝氨酸暴露、碘化丙啶摄取以及流式细胞术的真实计数来确定。相比之下，分别与针对远隔或紧邻区域的抗CD47单克隆抗体2D3或B6H12培养后未观察到细胞凋亡。如对缺乏这些信号通路的Jurkat细胞系变体的研究所证明，CD47介导的细胞死亡独立于CD3、CD4、CD45或p56lck的参与。然而，CD3ε和CD47的共同连接增强了具有功能性CD3的Jurkat细胞上磷脂酰丝氨酸的外化。此外，正常T细胞需要预先激活才能对CD47诱导的细胞凋亡作出反应。CD47介导的细胞死亡似乎独立于Fas或TNF受体信号传导进行，并且不涉及特征性DNA片段化，也不需要白细胞介素-1β转化酶样蛋白酶或CPP32。综上所述，我们的数据表明，在适当条件下，CD47激活导致非常快速的T细胞死亡，显然是由一种新的凋亡途径介导的。因此，CD47可能在控制活化T细胞的命运中起关键作用。
