The Interuniversity Messerli Research Institute of the University of Veterinary Medicine Vienna, Medical University Vienna and University Vienna, Vienna, Austria; Institute of Pathophysiology and Allergy Research, Center of Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria.
The Interuniversity Messerli Research Institute of the University of Veterinary Medicine Vienna, Medical University Vienna and University Vienna, Vienna, Austria; Laboratory Medicine and Immunology Department, Faculty of Medicine, Menoufia University, Menoufia, Egypt.
J Allergy Clin Immunol. 2021 Jan;147(1):321-334.e4. doi: 10.1016/j.jaci.2020.05.023. Epub 2020 May 30.
Beta-lactoglobulin (BLG) is a bovine lipocalin in milk with an innate defense function. The circumstances under which BLG is associated with tolerance of or allergy to milk are not understood.
Our aims were to assess the capacity of ligand-free apoBLG versus loaded BLG (holoBLG) to protect mice against allergy by using an iron-quercetin complex as an exemplary ligand and to study the molecular mechanisms of this protection.
Binding of iron-quercetin to BLG was modeled and confirmed by spectroscopy and docking calculations. Serum IgE binding to apoBLG and holoBLG in children allergic to milk and children tolerant of milk was assessed. Mice were intranasally treated with apoBLG versus holoBLG and analyzed immunologically after systemic challenge. Aryl hydrocarbon receptor (AhR) activation was evaluated with reporter cells and Cyp1A1 expression. Treated human PBMCs and human mast cells were assessed by fluorescence-activated cell sorting and degranulation, respectively.
Modeling predicted masking of major IgE and T-cell epitopes of BLG by ligand binding. In line with this modeling, IgE binding in children allergic to milk was reduced toward holoBLG, which also impaired degranulation of mast cells. In mice, only treatments with holoBLG prevented allergic sensitization and anaphylaxis, while sustaining regulatory T cells. BLG facilitated quercetin-dependent AhR activation and, downstream of AhR, lung Cyp1A1 expression. HoloBLG shuttled iron into monocytic cells and impaired their antigen presentation.
The cargo of holoBLG is decisive in preventing allergy in vivo. BLG without cargo acted as an allergen in vivo and further primed human mast cells for degranulation in an antigen-independent fashion. Our data provide a mechanistic explanation why the same proteins can act either as tolerogens or as allergens.
β-乳球蛋白（BLG）是牛奶中的一种牛脂球蛋白，具有先天的防御功能。目前尚不清楚 BLG 与牛奶耐受或过敏相关的情况。
我们旨在评估配体自由的脱载 BLG（apoBLG）与负载 BLG（holoBLG）在使用铁-槲皮素复合物作为典型配体的情况下保护小鼠免受过敏的能力，并研究这种保护的分子机制。
通过光谱和对接计算对 BLG 与铁-槲皮素的结合进行了建模和确认。评估了对牛奶过敏和耐受的儿童血清 IgE 与 apoBLG 和 holoBLG 的结合。用 apoBLG 和 holoBLG 对经鼻处理的小鼠进行了系统挑战后的免疫学分析。用报告细胞评估芳香烃受体（AhR）的激活，并用 Cyp1A1 表达进行分析。通过荧光激活细胞分选和脱颗粒分别评估处理后的人 PBMC 和人肥大细胞。
模型预测配体结合会掩盖 BLG 的主要 IgE 和 T 细胞表位。与该模型一致，对牛奶过敏的儿童对 holoBLG 的 IgE 结合减少，这也损害了肥大细胞的脱颗粒。在小鼠中，只有用 holoBLG 处理才能预防过敏致敏和过敏反应，同时维持调节性 T 细胞。BLG 促进了槲皮素依赖性 AhR 激活，并且在 AhR 下游，肺 Cyp1A1 表达。holoBLG 将铁转运到单核细胞中，并损害了它们的抗原呈递。
holoBLG 的货物在预防体内过敏中起决定性作用。无货物的 BLG 在体内充当过敏原，并以抗原非依赖性方式进一步引发人类肥大细胞脱颗粒。我们的数据提供了一个机制解释，说明为什么相同的蛋白质可以作为耐受原或过敏原。
