Laboratory of Human Immunology and Infectious Disease, Graduate Institute of Clinical Medical Sciences, Chang Gung University, Taoyuan, Taiwan.
Division of Biophysics, Department of Biology, University of Osnabruck, Osnabruck, Germany.
J Exp Med. 2022 Sep 5;219(9). doi: 10.1084/jem.20212126. Epub 2022 Jul 14.
Anti-interferon (IFN)-γ autoantibodies (AIGAs) are a pathogenic factor in late-onset immunodeficiency with disseminated mycobacterial and other opportunistic infections. AIGAs block IFN-γ function, but their effects on IFN-γ signaling are unknown. Using a single-cell capture method, we isolated 19 IFN-γ-reactive monoclonal antibodies (mAbs) from patients with AIGAs. All displayed high-affinity (KD < 10-9 M) binding to IFN-γ, but only eight neutralized IFN-γ-STAT1 signaling and HLA-DR expression. Signal blockade and binding affinity were correlated and attributed to somatic hypermutations. Cross-competition assays identified three nonoverlapping binding sites (I-III) for AIGAs on IFN-γ. We found that site I mAb neutralized IFN-γ by blocking its binding to IFN-γR1. Site II and III mAbs bound the receptor-bound IFN-γ on the cell surface, abolishing IFN-γR1-IFN-γR2 heterodimerization and preventing downstream signaling. Site III mAbs mediated antibody-dependent cellular cytotoxicity, probably through antibody-IFN-γ complexes on cells. Pathogenic AIGAs underlie mycobacterial infections by the dual blockade of IFN-γ signaling and by eliminating IFN-γ-responsive cells.
抗干扰素 (IFN)-γ 自身抗体 (AIGAs) 是导致迟发性免疫缺陷伴播散性分枝杆菌和其他机会性感染的致病因素。AIGAs 阻断 IFN-γ 功能，但它们对 IFN-γ 信号的影响尚不清楚。我们使用单细胞捕获方法从 AIGAs 患者中分离出 19 种 IFN-γ 反应性单克隆抗体 (mAb)。所有 mAb 均显示出对 IFN-γ 的高亲和力（KD < 10-9 M）结合，但只有 8 种 mAb 能中和 IFN-γ-STAT1 信号和 HLA-DR 表达。信号阻断和结合亲和力相关，并归因于体细胞超突变。交叉竞争测定确定了 AIGAs 在 IFN-γ 上的三个非重叠结合位点 (I-III)。我们发现，位点 I mAb 通过阻断其与 IFN-γR1 的结合来中和 IFN-γ。位点 II 和 III mAb 结合细胞表面结合受体的 IFN-γ，从而阻止 IFN-γR1-IFN-γR2 异二聚体形成并阻止下游信号。位点 III mAb 介导抗体依赖性细胞毒性，可能是通过细胞上的抗体-IFN-γ 复合物。致病性 AIGAs 通过双重阻断 IFN-γ 信号和消除 IFN-γ 反应性细胞，导致分枝杆菌感染。
