Therapeutic potential of sialylated Pemphigoid Disease autoantibodies

近年来，越来越多的证据表明，IgG抗体（Abs）具有促炎或抗炎效应功能，这些潜力主要依赖于其双触角Fc n -糖苷链的末端糖段，该末端糖段与两条重链的Asp297偶联。其中，抗炎IgG抗体的Fc n -糖苷链含有末端半乳糖基和额外的唾液基片段，分别分为半乳糖基化和唾液基化IgG抗体。没有这些末端糖残基的IgG抗体被称为无半乳糖化，并在类风湿关节炎中执行促炎作用，如IgG自身抗体（AAbs）。这些差异末端糖部分所起的分子机制仍然是难以捉摸的。本文中，差异糖基化的IgG抗体不仅针对经典的Fcy受体，还针对c型凝集素受体（CLR）家族的成员。例如，激活Fcy受体和甘露糖受体被认为可以介导半乳糖化IgG抗体、Dectin-1和IgG抑制受体FcyRIIB对半乳糖化IgG抗体的作用，唾液化IgG抗体可以通过SIGN-R1 （DC-SIGN）和DCIR主要独立于FcyRIIB。由于半乳糖化和半乳糖化/唾液化IgG抗体的相反作用，假设它们在抗原特异性IgG抗体池中的相对频率可以决定是否产生促炎免疫反应，并可能作为表征抗原特异性免疫反应的最有价值的诊断标志物。与这一观点一致，我们发现初步证据表明，在活动性BP患者的抗XVII型胶原IgG抗体中，无半乳糖化IgG抗体占主导地位。同时，利用我们的被动AAb转移EBA小鼠模型，我们已经发现证据表明，在疾病的效应期，半乳糖化和半乳糖化IgG抗体分别具有促炎和抗炎作用。因此，从其他致病性的抗VII型胶原IgG抗体中去除糖苷链完全消除了皮肤炎症。相反，应用含有半乙酰基化IgG抗体的免疫复合物，通过Dectin-1与Fc¿RIIB在中性粒细胞上的交联机制抑制皮肤炎症。相比之下，唾液化IgG抗体在PD皮肤炎症效应期的额外作用尚未得到解决。项目4的主要目的是研究未半乳糖化、半乳糖化和唾液化的IgG抗体在PD及其受体的效应期，特别是对中性粒细胞的激活或抑制潜力。这些研究对于了解PD皮肤炎症的出现至关重要，也将阐明唾液化IgG抗体是否可以用于治疗PD患者的自身抗原特异性方式。我们的研究旨在为PD患者开发一种新的治疗策略，即患者自行获得、体外唾液化和再应用的IgG抗体。

In recent years, evidence has accumulated that IgG antibodies (Abs) can have pro- or antiinflammatory effector functions and that these potentials critically depend on the terminal sugar moieties of their biantennary Fc N-glycoside chains coupled to Asp297 of both heavy chains. Herein, the Fc N-glycoside chains of anti-inflammatory IgG Abs contain terminal galactosyl and additional sialyl moieties and are categorized into galactosylated and sialylated IgG Abs, respectively. IgG Abs without these terminal sugar residues are referred to as agalactosylated and execute proinflammatory actions such as IgG autoantibodies (AAbs) in rheumatoid arthritis. The molecular mechanisms enacted by these differential terminal sugar moieties are still largely elusive. Herein, differentially glycosylated IgG Abs not only target the classical Fcy receptors, but also members of the C-type lectin receptor (CLR) family. Activating Fcy receptors and the mannose receptor, for instance, have been suggested to mediate effects of agalactosylated IgG Abs, Dectin-1 and the IgG inhibitory receptor FcyRIIB those of galactosylated IgG Abs, and sialylated IgG Abs can act primarily independent of FcyRIIB through SIGN-R1 (DC-SIGN) and DCIR. Due to the opposite effects of agalactosylated and galactosylated/sialylated IgG Abs, their relative frequencies in the pool of antigen-specific IgG Abs is hypothesized to decide whether a proinflammatory immune response is mounted and may serve as most valuable diagnostic marker to characterize an antigen-specific immune response. In line with this notion, we have found preliminary evidence that agalactosylated IgG Abs are dominant among anti-type XVII collagen IgG AAbs in patients with active BP. In parallel, using our passive AAb transfer EBA mouse model, we have found evidence for both proinflammatory and antiinflammatory effects of agalactosylated and galactosylated IgG Abs, respectively, in the effector phase of the disease. Thus, removal of the glycoside chains from otherwise pathogenic anti-type VII collagen IgG AAbs completely abrogated skin inflammation. Conversely, application of immune complexes containing galactosylated IgG Abs suppressed skin inflammation by a mechanism including crosslinking of Dectin-1 with Fc¿RIIB on neutrophils. In contrast, the additional actions of sialylated IgG Abs in the effector phase of PD skin inflammation have not been addressed. The main aim of Project 4 is to investigate the activating or inhibitory potential of agalactosylated, galactosylated and sialylated IgG AAbs, respectively, in the effector phase of PD and their receptors, especially on neutrophils. These studies will be essential to understand the emergence of PD skin inflammation and will also clarify whether sialylated IgG AAbs can be used to treat PD patients in an autoantigen-specific manner. Our research aims to develop a new therapeutic strategy for PD patients with patient self-derived, ex vivo sialylated and re-applied IgG AAbs.