Hormonal control of IgG galactosylation in murine arthritis

说明书(申请人提供)：人免疫球蛋白G(IgG)的效应器功能依赖于抗体Fc部分内部的两个糖链。成人类风湿性关节炎(RA)在这些糖链中表现出一个特征的异常：更高比例的抗体使用缺乏末端半乳糖的糖型。这种抗体可以更有效地修复补体，因此更有可能引发组织炎症。然而，影响抗体糖基化的因素尚不清楚。在对类风湿关节炎患者的免疫球蛋白多糖的研究过程中，我们发现了令人信服的证据，即激素环境是体内免疫球蛋白多糖结构的关键决定因素。在这里，我们展示了我们可以在炎症性关节炎的小鼠K/BxN模型中模拟这种人类生理学的关键方面，从而能够进行详细的机制探索。因此，我们提出了两个目标。首先，我们将通过对培养的B细胞和关节炎前期K/BxN小鼠进行激素处理，并研究产生的Ig G糖化形式，来研究引起Ig G糖基化变化的内分泌因素。其次，我们将通过一系列实验，将荷尔蒙操控的K/BxN小鼠的免疫球蛋白转移到正常受体动物身上，研究激素驱动的免疫球蛋白糖基化改变对关节炎的体内重要性。我们期望观察到的差异中的葡聚糖的作用将通过对免疫球蛋白的体外酶促操作来评估，我们进一步期望通过这些实验来明确回答特定的糖链变化在致病抗体的关节致病性中的重要性。因此，这些研究将有助于理解抗体糖基化的基本生物学，为炎性关节炎的性别差异提供新的线索，并确定是否以及如何将免疫球蛋白多糖用于类风湿关节炎和相关疾病的治疗。 与公共卫生相关：现在许多证据表明，抗体在导致类风湿性关节炎(RA)关节炎症和破坏的一连串事件中起着关键作用。我们已经发现，抗体上附着的糖结构的变化--在类风湿关节炎中观察到的变化，并倾向于使抗体更具促炎作用--在人类受到荷尔蒙的控制。这项提案要求支持开发工具，在关节炎的小鼠模型上实验性地探索这一观察。我们的长期目标是了解抗体糖在类风湿性关节炎中的原因和重要性，了解糖的变化是否有助于疾病发病率的性别差异，并探索操纵糖类可能成为类风湿关节炎和相关疾病的新治疗方法的可能性。

DESCRIPTION (provided by applicant): The effector functions of human immunoglobulin G (IgG) depend on two glycans internal to the Fc portion of the antibody. Adults with rheumatoid arthritis (RA) exhibit a characteristic abnormality in these glycans: a higher proportion of antibodies employ glycoforms lacking terminal galactose. Such antibodies fix complement more efficiently and may therefore be more likely to incite tissue inflammation. However, the factors governing antibody glycosylation are not understood. In the course of studies into IgG glycans in RA patients, we have uncovered compelling evidence that hormonal milieu is a key in vivo determinant of IgG glycan structure. Here, we show that we can model key aspects of this human physiology in the murine K/BxN model of inflammatory arthritis, enabling detailed mechanistic exploration. We therefore propose two Aims. First, we will investigate the endocrine factors that induce changes in IgG glycosylation by subjecting cultured B cells and pre-arthritic K/BxN mice to hormonal manipulation and studying the resulting IgG glycoforms. Second, we will investigate the in vivo importance of hormone-driven IgG glycosylation changes to arthritis through a series of experiments in which IgG from hormonally-manipulated K/BxN mice is transferred to normal recipient animals. The role of glycans in the differences we expect to observe will be evaluated by ex vivo enzymatic manipulation of the IgG, experiments which we further anticipate to answer definitively the importance of specific glycan changes in the arthritogenicity of pathogenic antibodies. These studies will therefore contribute to the understanding of the basic biology of antibody glycosylation, shed fresh light on gender discrepancies in inflammatory arthritis, and determine whether and how IgG glycans might be manipulated for the treatment of RA and related diseases. PUBLIC HEALTH RELEVANCE: Much evidence now points to a key role for antibodies in the chain of events that leads to joint inflammation and destruction in rheumatoid arthritis (RA). We have found that changes in the structure of sugars attached to antibodies - changes observed in RA, and that tend to make antibodies more pro-inflammatory - are under hormonal control in humans. This proposal requests support to develop tools to explore this observation experimentally in a mouse model of arthritis. Our long-term goals are to understand the cause and importance of antibody sugars in RA, to learn whether sugar changes contribute to gender differences in disease incidence, and to explore the possibility that manipulation of sugars could be a new therapeutic approach to RA and related diseases.