Stingl G, Maurer D
Department of Dermatology, University of Vienna Medical School, Austria.
Int Arch Allergy Immunol. 1997 May-Jul;113(1-3):24-9. doi: 10.1159/000237499.
In atopic individuals, cutaneous antigen-presenting cells (APC), i.e. Langerhans' cells (LC) and dermal dendritic cells (DDC), frequently display anti-IgE reactivity. While earlier observations suggested that this phenomenon results from the binding of (complexed) IgE to the low affinity IgE receptor (Fc epsilonRII/CD23), recent evidence exists that LC and DDC, as well as peripheral blood dendritic cells and monocytes from atopic individuals, can bind monomeric IgE via the high-affinity receptor for IgE (Fc epsilonRI). We have now found that Fc epsilonRI, both quantitatively and qualitatively, is the pivotal serum IgE-binding structure on APC of atopic individuals, that Fc epsilonRI on APC functions as allergen-focusing molecule and that allergens are more efficiently taken up, processed and presented to T cells following targeting to APC via Fc epsilonRI compared to allergen binding to APC in the conventional manner. In vivo, Fc epsilonRI-IgE-dependent allergen presentation may critically lower atopic individuals' threshold to mount allergen-specific T cell responses. This would result in the perpetuation of allergen-specific IgE production (type I reactions) and perhaps even in the occurrence of T-cell-mediated delayed-type hypersensitivity reactions in allergen-exposed tissues.
在特应性个体中，皮肤抗原呈递细胞（APC），即朗格汉斯细胞（LC）和真皮树突状细胞（DDC），经常表现出抗IgE反应性。虽然早期观察结果表明这种现象是由于（复合的）IgE与低亲和力IgE受体（FcεRII/CD23）结合所致，但最近有证据表明，LC和DDC以及特应性个体的外周血树突状细胞和单核细胞可以通过IgE的高亲和力受体（FcεRI）结合单体IgE。我们现在发现，FcεRI无论在数量上还是质量上，都是特应性个体APC上关键的血清IgE结合结构，APC上的FcεRI作为变应原聚焦分子发挥作用，并且与变应原以传统方式结合到APC相比，变应原通过FcεRI靶向至APC后能更有效地被摄取、加工并呈递给T细胞。在体内，FcεRI-IgE依赖性变应原呈递可能会严重降低特应性个体引发变应原特异性T细胞反应的阈值。这将导致变应原特异性IgE产生（I型反应）持续存在，甚至可能导致在暴露于变应原的组织中发生T细胞介导的迟发型超敏反应。
