Blais David R, Vascotto Sandy G, Griffith May, Altosaar Illimar
Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ontario, Canada.
Invest Ophthalmol Vis Sci. 2005 Nov;46(11):4235-44. doi: 10.1167/iovs.05-0543.
Lipopolysaccharide (LPS) is one of the most powerful bacterial virulence factors in terms of proinflammatory properties and is likely to contribute to corneal bacterial keratitis. Better understanding of the spatial expression of the LPS receptor components at the tear-corneal interface might facilitate enhanced functions of the LPS receptor complex in ocular defense against Gram-negative infections.
The expression of LPS-binding protein (LBP), CD14, toll-like receptor (TLR)-4, and MD-2 in human lacrimal glands, reflex tears, and corneal epithelia was examined by ELISA, RT-PCR, Western blot analysis, and immunofluorescence. The release of proinflammatory cytokines after the activation of primary and immortalized corneal epithelial cells with LPS and human tears was measured by ELISA.
LBP and CD14 proteins were detected in reflex human tears. Human lacrimal glands and corneal epithelia expressed LBP, CD14, TLR4, and MD-2 mRNAs and proteins. In the corneal epithelium, LBP was mainly expressed by superficial and basal epithelial cells, whereas CD14, TLR4, and MD-2 expression were limited to the wing and basal epithelial cells. In a dose-dependant manner, tear CD14 and LBP mediated the secretion of interleukin (IL)-6 and IL-8 by corneal epithelia cells when challenged with LPS.
Tear CD14 and LBP complemented the LPS receptor complex expressed by the corneal epithelia to trigger an immune response in the presence of LPS. The complementation of these tear and corneal immune proteins could play an important role in LPS recognition and signaling and, therefore, could modulate ocular innate immunity.
就促炎特性而言，脂多糖（LPS）是最强大的细菌毒力因子之一，可能与角膜细菌性角膜炎有关。更好地了解泪液-角膜界面处LPS受体成分的空间表达，可能有助于增强LPS受体复合物在眼部抵御革兰氏阴性感染中的功能。
通过酶联免疫吸附测定（ELISA）、逆转录-聚合酶链反应（RT-PCR）、蛋白质印迹分析和免疫荧光法，检测人泪腺、反射性泪液和角膜上皮中LPS结合蛋白（LBP）、CD14、Toll样受体（TLR）-4和MD-2的表达。通过ELISA测定用LPS和人泪液激活原代和永生化角膜上皮细胞后促炎细胞因子的释放。
在人反射性泪液中检测到LBP和CD14蛋白。人泪腺和角膜上皮表达LBP、CD14、TLR4和MD-2的信使核糖核酸（mRNA）和蛋白质。在角膜上皮中，LBP主要由表层和基底上皮细胞表达，而CD14、TLR4和MD-2的表达仅限于翼状和基底上皮细胞。当受到LPS刺激时，泪液中的CD14和LBP以剂量依赖的方式介导角膜上皮细胞分泌白细胞介素（IL）-6和IL-8。
泪液中的CD14和LBP补充了角膜上皮表达的LPS受体复合物，以在存在LPS的情况下触发免疫反应。这些泪液和角膜免疫蛋白的互补作用可能在LPS识别和信号传导中起重要作用，因此可能调节眼部固有免疫。
