保护性自身抗体在维持体内平衡，与临床的相关性和治疗潜力方面受到广泛关注。最近的研究表明，IgG4自身抗体在系统性红斑狼疮(SLE)和类风湿关节炎(RA)中起重要作用。一方面，IgG4自身抗体可以与其他类型的免疫球蛋白(例如，IgG1，IgG2a)竞争结合自身抗原以形成非炎性免疫复合物(IC)，其由于与Fc受体和C1补体分子的低亲和力低，诱导免疫应答的能力有限，进而降低SLE和RA中的炎症反应。另一方面，IgG4的CH2结构域，在抗体与自身抗原结合后可能成为RA中类风湿因子(RF)的结合靶点。这一含有RF-IgG4-自身抗原的更大的免疫复合物可以强烈诱导免疫应答并引起RA的组织损伤。此外，本文还对IgG4-IgG1(IgG4-IgG2或IgG4-IgG3)-复合物和双特异性IgG4在SLE和RA中的作用进行了综述。总之，IgG4自身抗体可以作为SLE和RA发病机制的监控指标，甚至可以成为SLE的一种治疗方法。

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附原文：

ABSTRACT

Protective autoantibodies in homeostasis, clinical relevance, and therapeutic potential have gained wide attention. Recent studies showed that IgG4 autoantibodies play crucial roles in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). In one aspect, IgG4 autoantibodies can bind autoantigens in competition with other classes of immunoglobulins (e.g., IgG1, IgG2a) to form non-inflammatory immune-complexes (ICs), which have a limited ability to induce immune responses because of the low affinity of IgG4 for both Fc receptors and the C1 complement molecule, resulting in reduced inflammatory response in SLE and RA. In another aspect, the CH2 domain of IgG4, post antibody binding with autoantigens, might become a target for rheumatoid factors (RFs) in RA. The resultant bigger ICs containing RF-IgG4-autoantigens were shown to strongly induce immune responses and to cause tissue damage in RA. In addition, the roles of IgG4-IgG1 (IgG4-IgG2 or IgG4-IgG3)-complexes and bispecific IgG4 in SLE and RA are also reviewed. Overall, IgG4 autoantibodies may act as a monitor for the pathogenesis in SLE and RA and even as a treatment for SLE.

引自：Pan Q, Lan Q, Peng Y, et al. Nature, functions, and clinical implications of IgG4 autoantibodies in systemic lupus erythematosus and rheumatoid arthritis. Discov Med. 2017; 23(126): 169-174.