Brett S J, Rowan W, Smith M, Bartholomew M, Tite J P
Immunology Unit, Glaxo-Wellcome Medicines Research Centre, Stevenage, UK.
Immunology. 1997 Jul;91(3):346-53. doi: 10.1046/j.1365-2567.1997.00265.x.
A fully humanized immunoglobulin G1 (IgG1) anti-CD4 monoclonal antibody is currently being evaluated in phase I/II clinical trials for rheumatoid arthritis. In order to understand the mode of action of this antibody in vivo, we have carried out a detailed functional analysis in vitro of the effects of this antibody on T-cell activation. The anti-CD4 antibody was found to inhibit both antigen-specific responses involving recognition of human leucocyte antigen (HLA) class II and processed antigenic peptides as well as non-class II dependent responses via anti-CD3 antibodies. The antibody did not cause total blockade of T-cell proliferation, but rather induced a shift in the dose-response curve, decreasing the sensitivity of cells to antigen or anti-CD3-mediated stimulation. The antibody appears to allow at least a partial early signal into the T cell as it does not inhibit the increase in tyrosine phosphorylation induced by anti-CD3 antibodies. A comparison of the intact antibody with that of either the F(ab')2 fragment or an engineered non-Fc receptor (FcR) binding form revealed that the intact antibody was the most effective at inhibiting proliferation of resting peripheral blood CD4+ T cells. However, this difference was only apparent when excess antibody was removed from culture prior to antigen or anti-CD3 mediated stimulation. The intact antibody induced both CD4 down-modulation and increases in CD4-associated tyrosine phosphorylation of resting CD4+ T cells, which were not seen with the non-FcR binding versions, which may account for the enhanced potency of the intact antibody at inhibiting T-cell activation. Interestingly, the anti-CD4 antibody induced a differential effect on activated CD4+ T cell clones compared with resting CD4+ T cells with respect to degree of CD4 cross-linking required to induce functional effects in the T cell. Both intact and non-FcR binding antibodies were equally effective at inhibiting T-cell proliferation of activated T-cell clones. In addition CD4 down-modulation and increased CD4-associated tyrosine phosphorylation were observed with T-cell clones in the absence of secondary cross-linking. Such observations may be of relevance when studying the effects of the antibody at sites of inflammation, where there will be CD4+ T cells of differing activation states as well as varying numbers of FcR positive cells.
一种完全人源化的免疫球蛋白G1（IgG1）抗CD4单克隆抗体目前正在类风湿性关节炎的I/II期临床试验中进行评估。为了了解该抗体在体内的作用模式，我们对其在体外对T细胞活化的影响进行了详细的功能分析。发现抗CD4抗体既能抑制涉及识别人类白细胞抗原（HLA）II类和加工后的抗原肽的抗原特异性反应，也能抑制通过抗CD3抗体介导的非II类依赖性反应。该抗体并未导致T细胞增殖的完全阻断，而是引起剂量反应曲线的偏移，降低细胞对抗原或抗CD3介导刺激的敏感性。该抗体似乎允许至少部分早期信号进入T细胞，因为它不抑制抗CD3抗体诱导的酪氨酸磷酸化增加。完整抗体与F(ab')2片段或工程化的非Fc受体（FcR）结合形式的抗体进行比较，结果显示完整抗体在抑制静息外周血CD4+ T细胞增殖方面最有效。然而，只有在抗原或抗CD3介导刺激之前从培养物中去除过量抗体时，这种差异才明显。完整抗体诱导静息CD4+ T细胞的CD4下调和与CD4相关的酪氨酸磷酸化增加，而在非FcR结合形式的抗体中未观察到这种现象，这可能解释了完整抗体在抑制T细胞活化方面增强的效力。有趣的是，与静息CD4+ T细胞相比，抗CD4抗体对活化的CD4+ T细胞克隆诱导功能性效应所需的CD4交联程度产生了不同的影响。完整抗体和非FcR结合抗体在抑制活化T细胞克隆的T细胞增殖方面同样有效。此外，在没有二次交联的情况下，T细胞克隆也观察到了CD4下调和与CD4相关的酪氨酸磷酸化增加。在研究抗体在炎症部位的作用时，这些观察结果可能具有相关性，因为在炎症部位会存在不同活化状态的CD4+ T细胞以及数量各异的FcR阳性细胞。
