Brinkhaus Maximilian, Douwes Ruben G J, Bentlage Arthur E H, Temming A Robin, de Taeye Steven W, Tammes Buirs Matthias, Gerritsen Jacoline, Mok Juk Yee, Brasser Giso, Ligthart Peter C, van Esch Wim J E, Verheesen Peter, de Haard Hans, Rispens Theo, Vidarsson Gestur
Department of Experimental Immunohematology, Sanquin Research and Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, 1066 CX, Amsterdam, the Netherlands.
Department of Immunopathology, Sanquin Research and Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, 1066 CX Amsterdam, the Netherlands.
J Immunol. 2020 Dec 15;205(12):3456-3467. doi: 10.4049/jimmunol.2000961. Epub 2020 Nov 13.
Abs of the IgG isotype mediate effector functions like Ab-dependent cellular cytotoxicity and Ab-dependent cellular phagocytosis by Fc interactions with FcγRs and complement-dependent cytotoxicity upon IgG-Fc binding to C1q. In this study, we describe the crucial role of the highly conserved dual glycines at position 236-237 in the lower hinge region of human IgG, including the lack of one glycine as found in IgG2. We found several permutations in this region that either silence or largely abrogate FcγR binding and downstream FcγR effector functions, as demonstrated by surface plasmon resonance, Ab-dependent cellular phagocytosis, and Ab-dependent cellular cytotoxicity assays. Although the binding regions of FcγRs and C1q on the IgG-Fc largely overlap, IgG1 with a deletion of G236 only silences FcγR-mediated effector functions without affecting C1q-binding or activation. Several mutations resulted in only residual FcγRI binding with differing affinities that are either complement competent or silenced. Interestingly, we also found that IgG2, naturally only binding FcγRIIa, gains binding to FcγRI and FcγRIIIa after insertion of G236, highlighting the crucial importance of G236 in IgG for FcγR interaction. These mutants may become invaluable tools for FcγR-related research as well as for therapeutic purposes in which only complement-mediated functions are required without the involvement of FcγR.
IgG 同种型的抗体通过与 FcγR 的 Fc 相互作用介导效应功能，如抗体依赖性细胞毒性和抗体依赖性细胞吞噬作用，以及 IgG-Fc 与 C1q 结合后的补体依赖性细胞毒性。在本研究中，我们描述了人 IgG 下铰链区第 236 - 237 位高度保守的双甘氨酸的关键作用，包括 IgG2 中发现的缺少一个甘氨酸的情况。我们发现该区域的几种排列方式要么使 FcγR 结合沉默，要么在很大程度上消除 FcγR 结合及下游 FcγR 效应功能，表面等离子体共振、抗体依赖性细胞吞噬作用和抗体依赖性细胞毒性试验证明了这一点。尽管 FcγR 和 C1q 在 IgG-Fc 上的结合区域大部分重叠，但仅缺失 G236 的 IgG1 仅使 FcγR 介导的效应功能沉默，而不影响 C1q 结合或激活。几种突变导致仅残留具有不同亲和力的 FcγRI 结合，这些亲和力要么具有补体活性，要么沉默。有趣的是，我们还发现天然仅结合 FcγRIIa 的 IgG2 在插入 G236 后获得了与 FcγRI 和 FcγRIIIa 的结合，突出了 G236 在 IgG 与 FcγR 相互作用中的关键重要性。这些突变体可能成为 FcγR 相关研究以及仅需要补体介导功能而无需 FcγR 参与的治疗目的的宝贵工具。
