Department of Pathology, University of New Mexico, Albuquerque, NM 87131, USA.
J Immunol. 2010 Feb 1;184(3):1328-38. doi: 10.4049/jimmunol.0903071. Epub 2009 Dec 30.
Fc epsilonRI on mast cells form a synapse when presented with mobile, bilayer-incorporated Ag. In this study, we show that receptor reorganization within the contacting mast cell membrane is markedly different upon binding of mobile and immobilized ligands. Rat basophilic leukemia mast cells primed with fluorescent anti-DNP IgE were engaged by surfaces presenting either bilayer-incorporated, monovalent DNP-lipid (mobile ligand), or chemically cross-linked, multivalent DNP (immobilized ligand). Total internal reflection fluorescence imaging and electron microscopy methods were used to visualize receptor reorganization at the contact site. The spatial relationships of Fc epsilonRI to other cellular components at the synapse, such as actin, cholesterol, and linker for activation of T cells, were also analyzed. Stimulation of mast cells with immobilized polyvalent ligand resulted in typical levels of degranulation. Remarkably, degranulation also followed interaction of mast cells, with bilayers presenting mobile, monovalent ligand. Receptors engaged with mobile ligand coalesce into large, cholesterol-rich clusters that occupy the central portion of the contacting membrane. These data indicate that Fc epsilonRI cross-linking is not an obligatory step in triggering mast cell signaling and suggest that dense populations of mobile receptors are capable of initiating low-level degranulation upon ligand recognition.
当遇到可移动的双层整合 Ag 时，肥大细胞上的 Fc epsilonRI 形成突触。在这项研究中，我们表明，在结合可移动和固定配体时，接触肥大细胞膜内的受体重组明显不同。用荧光抗 DNP IgE 预致敏的大鼠嗜碱性白血病肥大细胞通过表面呈现双层整合的单价 DNP-脂质（可移动配体）或化学交联的多价 DNP（固定配体）来参与。全内反射荧光成像和电子显微镜方法用于可视化接触部位的受体重组。还分析了 Fc epsilonRI 与突触处其他细胞成分（如肌动蛋白、胆固醇和 T 细胞激活连接蛋白）的空间关系。用固定的多价配体刺激肥大细胞会导致典型的脱颗粒水平。值得注意的是，与呈现可移动单价配体的双层膜相互作用后，肥大细胞也会脱颗粒。与可移动配体结合的受体聚集成大的富含胆固醇的簇，占据接触膜的中心部分。这些数据表明，Fc epsilonRI 交联不是触发肥大细胞信号转导的必需步骤，并表明大量可移动受体能够在配体识别时引发低水平的脱颗粒。
