Jabado N, Le Deist F, Fisher A, Hivroz C
INSERM U 132, Hôpital, Necker-Enfants Malades, Paris, France.
Eur J Immunol. 1994 Nov;24(11):2646-52. doi: 10.1002/eji.1830241112.
The membrane glycoprotein CD4 is required for optimal antigen-mediated activation of CD4+ T cells restricted by class II molecules of the major histocompatibility complex (MHC). CD4 cross-linking by anti-CD4 antibodies or binding by human immunodeficiency virus (HIV) gp120 has been shown to inhibit antigen-dependent and -independent T cell activation, abrogating T cell proliferation, IL-2 synthesis and the increase in the intracellular calcium concentration. The molecular basis of these opposing phenomena is ill-defined. To characterize further the inhibitory role of the CD4 molecule, we investigated the effects of CD4 ligands on the transcription factors regulating the IL-2 gene enhancer and IL-2 synthesis. We first confirmed that pre-treatment of peripheral human CD4+ T lymphocytes by CD4 ligands, HIV gp120 or anti-CD4 monoclonal antibodies inhibited IL-2 production and cell proliferation, which was normally induced by an anti-CD3 antibody (UCHT1) plus a protein kinase C activator (PMA). Moreover, these CD4 ligands inhibited the proliferation and synthesis of IL-2 induced by activators bypassing membrane events, i.e. PMA and calcium ionophore, pointing to an active signaling pathway triggered by the CD4 molecule. Gp120 and anti-CD4 antibodies induced a specific, significant decrease in the binding activity of NF-AT, NF-kappa B and AP-1, three transcription factors regulating IL-2 gene enhancer activity, as demonstrated by electrophoretic mobility shift assays. Inhibition was similarly observed following cell activation by activators involving membrane events and those bypassing them. These results strongly suggest that the inhibition mediated by cross-linking of the CD4 molecule is at least partly due to negative signal down-regulating the availability of nuclear factors necessary for the regulation of IL-2 gene transcription.
主要组织相容性复合体（MHC）Ⅱ类分子限制的CD4⁺T细胞的最佳抗原介导激活需要膜糖蛋白CD4。抗CD4抗体对CD4的交联或人类免疫缺陷病毒（HIV）gp120的结合已被证明可抑制抗原依赖性和非依赖性T细胞激活，消除T细胞增殖、IL-2合成以及细胞内钙浓度的升高。这些相反现象的分子基础尚不明确。为了进一步表征CD4分子的抑制作用，我们研究了CD4配体对调节IL-2基因增强子和IL-2合成的转录因子的影响。我们首先证实，用CD4配体、HIV gp120或抗CD4单克隆抗体预处理外周人CD4⁺T淋巴细胞可抑制IL-2产生和细胞增殖，而这通常由抗CD3抗体（UCHT1）加蛋白激酶C激活剂（PMA）诱导。此外，这些CD4配体抑制了绕过膜事件的激活剂（即PMA和钙离子载体）诱导的IL-2增殖和合成，表明CD4分子触发了一条活跃的信号通路。如电泳迁移率变动分析所示，gp120和抗CD4抗体导致调节IL-2基因增强子活性的三种转录因子NF-AT、NF-κB和AP-1的结合活性特异性、显著降低。在通过涉及膜事件的激活剂和绕过膜事件的激活剂激活细胞后，同样观察到了抑制作用。这些结果强烈表明，CD4分子交联介导的抑制至少部分是由于负信号下调了调节IL-2基因转录所需的核因子的可用性。
