Yen A, Liu F T, Barrett K E, Gigli I
Department of Medicine, University of California, San Diego, School of Medicine 92103.
J Immunol. 1993 Jul 15;151(2):1003-11.
As previously reported, protoporphyrin plus long-wavelength UV light (PP/UVA) inhibits IgE-mediated degranulation of mouse bone marrow-derived mast cells, as assessed by measurement of the release of beta-hexosaminidase. This inhibitory effect was seen with cells sensitized with IgE either before or after PP/UVA treatment (57.8 and 55.3% inhibition, respectively). PP/UVA did not dissociate IgE already bound to cells as assessed either by measuring release of bound 125I-IgE or by flow cytometric analysis. Results from immunoadsorption followed by SDS-PAGE analysis suggested that PP/UVA treatment may cause stable conjugation of IgE to its receptor. In unsensitized cells, PP/UVA did not cause conjugation of the unoccupied Fc epsilon RI to other proteins in the plasma membrane. Nevertheless, Scatchard analysis revealed that PP/UVA decreased the number of Fc epsilon RI per cell by 37% (0.95 x 10(5) vs 1.51 x 10(5)/cell), whereas affinity of the receptor for IgE was comparable between PP/UVA-treated and untreated cells (3.40 nM vs 3.27 nM). Flow cytometric analysis also confirmed the decrease in Fc epsilon RI number in PP/UVA-treated unsensitized mouse bone marrow-derived mast cells. Although 84% of PP/UVA-treated and 82% of untreated cells expressed positive fluorescence when stained with FITC-conjugated IgE, fluorescence intensity was reduced by 40% after PP/UVA treatment. We conclude that PP/UVA alters the conformational structure and/or number of Fc epsilon RI expressed on the mast cell surface. This effect could potentially explain the ability of PP/UVA to inhibit mast cell secretory function and may be related to an ability of PP/UVA to alter the properties of the plasma membrane.
如先前报道，原卟啉加长波紫外线（PP/UVA）可抑制IgE介导的小鼠骨髓来源肥大细胞脱颗粒，这通过测量β-己糖胺酶的释放来评估。在用PP/UVA处理之前或之后用IgE致敏的细胞中均观察到这种抑制作用（分别为57.8%和55.3%的抑制率）。通过测量结合的125I-IgE的释放或流式细胞术分析评估，PP/UVA不会使已结合到细胞上的IgE解离。免疫吸附后进行SDS-PAGE分析的结果表明，PP/UVA处理可能导致IgE与其受体的稳定结合。在未致敏的细胞中，PP/UVA不会导致未占据的FcεRI与质膜中的其他蛋白质结合。然而，Scatchard分析显示，PP/UVA使每个细胞的FcεRI数量减少了37%（0.95×10⁵个/细胞对1.51×10⁵个/细胞），而PP/UVA处理组和未处理组细胞中受体对IgE的亲和力相当（3.40 nM对3.27 nM）。流式细胞术分析也证实了PP/UVA处理的未致敏小鼠骨髓来源肥大细胞中FcεRI数量的减少。尽管用异硫氰酸荧光素（FITC）偶联的IgE染色时，84%的PP/UVA处理细胞和82%的未处理细胞表达阳性荧光，但PP/UVA处理后荧光强度降低了40%。我们得出结论，PP/UVA改变了肥大细胞表面表达的FcεRI的构象结构和/或数量。这种效应可能潜在地解释了PP/UVA抑制肥大细胞分泌功能的能力，并且可能与PP/UVA改变质膜特性的能力有关。
