Product Testing of Immunological Biopharmaceuticals, Division of Immunology, Paul-Ehrlich-Institut, Langen, Germany.
Institute of Virology, Medical Center, University of Freiburg, Freiburg, Germany.
Eur J Immunol. 2019 Jul;49(7):1117-1126. doi: 10.1002/eji.201847924. Epub 2019 Apr 29.
The first-in-human clinical trial of the CD28-specific monoclonal antibody (mAb) TGN1412 resulted in a life-threatening cytokine release syndrome. Although TGN1412 was designed as IgG4, known for weak Fc:Fcγ receptor (FcγR) interactions, these interactions contributed to TGN1412-induced T-cell activation. Using cell lines (TFs) expressing human FcγRI, -IIa, -IIb, or -III, we show that TGN1412 and TGN1412 as IgG1 and IgG2 are bound by FcγRs as it can be deduced from literature. However, upon coculture of TGN1412-decorated T cells with TFs or human primary blood cells, we observed that binding capacities by FcγRs do not correlate with the strength of the mediated effector function. FcγRIIa and FcγRIIb, showing no or very minor binding to TGN1412, mediated strongest T cell proliferation, while high-affinity FcγRI, exhibiting strong TGN1412 binding, mediated hardly any T-cell proliferation. These findings are of biological relevance because we show that FcγRI binds TGN1412, thus prevents binding to FcγRIIa or FcγRIIb, and consequently disables T-cell proliferation. In line with this, FcγRI FcγRII but not FcγRI FcγRII monocytes mediate TGN1412-induced T-cell proliferation. Collectively, by using TGN1412 as example, our results indicate that binding of monomeric IgG subclasses does not predict the FcγR-mediated effector function, which has major implications for the design of therapeutic mAbs.
首例人源化 CD28 特异性单克隆抗体（mAb）TGN1412 的临床试验导致危及生命的细胞因子释放综合征。尽管 TGN1412 被设计为 IgG4，因其与 Fcγ 受体（FcγR）的弱相互作用而闻名，但这些相互作用导致了 TGN1412 诱导的 T 细胞激活。使用表达人 FcγRI、-IIa、-IIb 或 -III 的细胞系（TFs），我们表明 TGN1412 和 TGN1412 作为 IgG1 和 IgG2 可被 FcγR 结合，正如文献中推断的那样。然而，在 TGN1412 包被的 T 细胞与 TFs 或人原代血细胞共培养时，我们观察到 FcγR 的结合能力与介导的效应功能的强度不相关。FcγRIIa 和 FcγRIIb 对 TGN1412 的结合能力较弱或没有，介导最强的 T 细胞增殖，而高亲和力的 FcγRI 对 TGN1412 具有很强的结合能力，几乎不介导 T 细胞增殖。这些发现具有生物学相关性，因为我们表明 FcγRI 结合 TGN1412，从而阻止与 FcγRIIa 或 FcγRIIb 结合，并因此使 T 细胞增殖失活。与此一致的是，FcγRI FcγRII 而不是 FcγRI FcγRII 单核细胞介导 TGN1412 诱导的 T 细胞增殖。总之，我们的结果以 TGN1412 为例表明，单体 IgG 亚类的结合不能预测 FcγR 介导的效应功能，这对治疗性 mAb 的设计具有重要意义。
