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，这些抗体对过敏原具有特异性， 引发由肥大细胞和嗜碱性粒细胞介导的强有力的炎症反应。IgE与高亲和力的 受体（FcεRI）在这些过敏效应细胞上表达，使其成为一种关键的相互作用， 许多不同的过敏原特异性反应。目前使用的抗IgE治疗性抗体（奥马珠单抗） 治疗过敏性哮喘和慢性特发性荨麻疹患者。我们确定了 奥马珠单抗Fab与IgE-Fc结合，阐明奥马珠单抗如何阻断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，其不结合奥马珠单抗，但保留了与奥马珠单抗的相互作用， 高亲和力和低亲和力IgE受体。这种IgE糖变体可以与奥马珠单抗共同施用，以替代 细胞结合的IgE，用非反应性变体交换过敏原反应性IgE。这种细胞共处理 提供协同抑制，其在阻断嗜碱性粒细胞活化方面比单独的任一抑制剂更有效。我们 将单个额外的N-连接的糖基化位点并入IgE-Fc中的IgE糖变体也显示了 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 需要通过“过敏性”IgE直接竞争FceRI结合。我们假设碳水化合物特异性 抑制性受体，如Siglec家族的成员，可以被IgE糖变体接合以阻断免疫应答。 FcεRI信号传导。在本研究中，我们将探讨IgE糖基化对人类免疫球蛋白抑制的影响。 嗜碱性粒细胞活化，伴随和不伴随奥马珠单抗治疗，并通过以下方式确定机制： 所述IgE糖变体抑制变应性炎性细胞的FceRI依赖性活化。

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.