Horneff G, Guse A H, Schulze-Koops H, Kalden J R, Burmester G R, Emmrich F
Institut für Klinische Immunologie und Rheumatologie, Universität of Erlangen-Nürnberg, Germany.
Clin Immunol Immunopathol. 1993 Jan;66(1):80-90. doi: 10.1006/clin.1993.1011.
Clinical improvement after treatment with anti-CD4 antibodies has been documented in patients suffering from rheumatoid arthritis. This observation has stimulated the interest in effects induced by the in vivo application of anti-CD4 antibodies. Here, we have investigated features of CD4 modulation during and after anti-CD4 therapy with the monoclonal anti-body MAX.16H5. Depletion of circulating helper T cells was accompanied by modulation of the CD4 molecule down to 30% of the initial antigen density 1 hr after antibody infusion. However, despite the reappearance of CD4+ cells in the circulation CD4 remained down-modulated for up to 28 days without a significant residual anti-CD4 binding. Depletion of CD4+ cells as well as CD4 modulation were observed to a similar extent both in responders and non-responders to anti-CD4 therapy. Modulation of CD4 was more effective in vivo than in vitro with a mean reduction of CD4 density down to 46% in vitro. It was induced in varying degrees by all anti-CD4 antibodies investigated except for OKT4 and required viable monocytes in the case of MAX.16H5 and most of the anti-CD4 antibodies investigated. Supernatants from LPS-activated monocytes or the addition of monocytes that were freeze-fractioned or fixed monocytes did not substitute for this requirement. The effect was Fc-receptor dependent since F(ab)2 fragments of MAX.16H5 did not induce CD4 modulation. No significant co-modulation was found for a variety of T-cell surface antigens including CD2, CD3, CD8, CD45R, CD45RO, CD25, CDw29, and HLA-DR. In order to test functional effects, the influence of CD4 modulation on the increase of free cytosolic Ca2+ concentration ([Ca2+]i) stimulated via the T-cell receptor complex by an anti-CD3 antibody was studied. A significant inhibition was observed upon direct binding of anti-CD4 to its ligand. However, a diminished CD4 density alone as induced by in vivo modulation did not reduce, but rather enhanced the T cell receptor-mediated mobilization of [Ca2+]i in T cells of the patients. Taken together, no evidence was found that CD4 modulation per se could explain the beneficial effects of anti-CD4 therapy.
类风湿关节炎患者接受抗 CD4 抗体治疗后临床症状改善的情况已有文献记载。这一观察结果激发了人们对体内应用抗 CD4 抗体所诱导效应的兴趣。在此，我们用单克隆抗体 MAX.16H5 研究了抗 CD4 治疗期间及之后 CD4 调节的特征。循环辅助性 T 细胞的耗竭伴随着 CD4 分子的调节，在抗体输注后 1 小时，CD4 分子下调至初始抗原密度的 30%。然而，尽管循环中 CD4+细胞再度出现，但 CD4 持续下调长达 28 天，且无明显的抗 CD4 残留结合。在抗 CD4 治疗的应答者和非应答者中，CD4+细胞的耗竭以及 CD4 的调节程度相似。CD4 的调节在体内比在体外更有效，体外 CD4 密度平均降低至 46%。除 OKT4 外，所有研究的抗 CD4 抗体均能不同程度地诱导 CD4 调节，对于 MAX.16H5 和大多数研究的抗 CD4 抗体而言，这需要有活力的单核细胞。来自 LPS 激活的单核细胞的上清液，或添加经冷冻破碎或固定的单核细胞，均不能满足这一要求。该效应依赖于 Fc 受体，因为 MAX.16H5 的 F(ab)2 片段不会诱导 CD4 调节。对于包括 CD2、CD3、CD8、CD45R、CD45RO、CD25、CDw29 和 HLA-DR 在内的多种 T 细胞表面抗原，未发现明显的共调节。为了测试功能效应，研究了 CD4 调节对抗 CD3 抗体通过 T 细胞受体复合物刺激引起的游离胞质 Ca2+浓度（[Ca2+]i）升高的影响。当抗 CD4 直接与其配体结合时，观察到显著抑制。然而，体内调节单独诱导的 CD4 密度降低并未减少，反而增强了患者 T 细胞中 T 细胞受体介导的[Ca2+]i 动员。综上所述，没有证据表明 CD4 调节本身可以解释抗 CD4 治疗的有益效果。
