Suppression of basophil activation by IgE glycovariants

项目摘要 大多数过敏反应是由免疫球蛋白E(IgE)抗体引起的，这种抗体是针对过敏原和 触发由肥大细胞和嗜碱性粒细胞介导的强烈炎症反应。免疫球蛋白与高亲和力结合 受体(FcεRI)在这些过敏效应细胞上表达，使这一关键相互作用普遍存在于 许多不同的过敏原特异性反应。目前使用的是抗IgE治疗性抗体(Omalizumab) 用于治疗过敏性哮喘和慢性特发性荨麻疹患者。我们确定了 Omalizumab Fab与IgE-Fc结合，阐明omalizumab如何阻止IgE与两种受体的相互作用。 我们还设计了一种IgE-Fc糖基化突变体，它不与奥马珠单抗结合，但保留了与 高、低亲和力的IgE受体。这种IgE糖变异体可以与奥马珠单抗联合使用，以取代 与细胞结合的IgE，与非反应性变异体交换过敏原反应性IgE。细胞的这种共处理 提供协同抑制，在阻止嗜碱性细胞激活方面比单独使用任何一种抑制剂都更有效。我们的 Ige糖变异体在IgE-Fc中加入了一个额外的N-连接糖基化位点，也显示出 与野生型IgE-Fc相比，其自身对嗜碱性粒细胞的抑制作用更强。这种抑制并不是 需要通过“过敏性”IgE直接竞争FceRI结合。我们假设碳水化合物专一性 抑制性受体，如Siglec家族的成员，可能被IgE糖变异体激活以阻断 FCεRI信令。在这项建议中，我们将探讨IgE糖基化对人血清白蛋白抑制的影响。 在奥马珠单抗治疗和不联合奥马珠单抗治疗的情况下，嗜碱性细胞的激活，并通过 哪些IgE糖变异体抑制FceRI依赖的变态反应性炎症细胞的激活。

Project Summary Most allergic reactions are caused by immunoglobulin E (IgE) antibodies that are specific for allergens and trigger potent inflammatory responses mediated by mast cells and basophils. IgE binds to the high affinity receptor (FcεRI) expressed on these allergic effector cells, making this a key interaction that is common to many different allergen-specific responses. The anti-IgE therapeutic antibody (Omalizumab) is currently used to treat allergic asthma and chronic idiopathic urticaria in patients. We determined the structure of the Omalizumab Fab bound to the IgE-Fc, clarifying how Omalizumab blocks IgE interactions with both receptors. We also designed an IgE-Fc glycosylation mutant that does not bind Omalizumab, but retains interactions with high and low affinity IgE receptors. This IgE glycovariant can be co-administered with Omalizumab, to replace the cell-bound IgE, exchanging allergen-reactive IgE with a non-reactive variant. This co-treatment of cells provides synergistic inhibition that is more potent at blocking basophil activation than either inhibitor alone. Our IgE glycovariant, which incorporates a single additional N-linked glycosylation site into the IgE-Fc, also shows more potent inhibition of basophils on its own as compared to the wild type IgE-Fc. The inhibition does not require direct competition for FceRI binding by “allergic” IgE. We hypothesize that carbohydrate-specific inhibitory receptors, such as members of the Siglec family, may be engaged by the IgE glycovariant to block FcεRI signaling. In this proposal, we will explore the impact of IgE glycosylation on the inhibition of human basophil activation, both with and without concomitant Omalizumab treatment, and identify the mechanisms by which IgE glycovariants suppress FceRI-dependent activation of allergic inflammatory cells.