Cubitt C L, Lausch R N, Oakes J E
Department of Microbiology and Immunology, College of Medicine, University of South Alabama, Mobile 36688-0002.
J Immunol. 1994 Jul 1;153(1):232-40.
Neutrophils and Langerhans cells participate in inflammatory reactions within the human cornea. Because granulocyte-macrophage (GM)-CSF is a chemotactic and activating factor for these two cell types, we investigated whether this cytokine is produced by human corneal epithelial cells and corneal fibroblasts. Cultures of each cell type were exposed to increasing concentrations of IL-1 alpha or TNF-alpha. Culture supernatants were assayed for GM-CSF by using ELISA and cytokine mRNA levels were monitored by using reverse transcriptase-PCR. IL-1 alpha treatment of both cell types resulted in the appearance of GM-CSF mRNA and the production of > 480 pg protein/10(6) cells. However, TNF-alpha treatment yielded divergent results. Stimulation of epithelial cells with TNF-alpha resulted in the appearance of > 560 GM-CSF mRNA molecules per cell and production of > 1300 pg GM-CSF/10(6) cells. In contrast, stimulation of corneal fibroblasts resulted in < 16 GM-CSF mRNA molecules/cell and < 60 pg GM-CSF/10(6) cells. Binding studies with 125I-labeled TNF-alpha revealed that corneal fibroblasts had as many receptor sites as did corneal epithelial cells. Furthermore, corneal fibroblasts could respond to TNF-alpha-receptor-mediated signal transduction because they produced nanogram amounts of IL-6 after being treated with this cytokine. The results suggest that both cell types synthesize GM-CSF in response to IL-1 alpha, but that only corneal epithelial cells produce significant amounts of GM-CSF after TNF-alpha exposure. Differences in the responses of the two cell types to TNF-alpha may reflect a means of limiting accumulation of neutrophils and Langerhans cells and, thus, minimize corneal damage.
中性粒细胞和朗格汉斯细胞参与人体角膜内的炎症反应。由于粒细胞-巨噬细胞（GM）-集落刺激因子是这两种细胞类型的趋化和激活因子，我们研究了这种细胞因子是否由人角膜上皮细胞和角膜成纤维细胞产生。将每种细胞类型的培养物暴露于浓度递增的白细胞介素-1α或肿瘤坏死因子-α中。通过酶联免疫吸附测定法（ELISA）检测培养上清液中的GM-集落刺激因子，并使用逆转录-聚合酶链反应监测细胞因子mRNA水平。用白细胞介素-1α处理这两种细胞类型均导致GM-集落刺激因子mRNA的出现以及每10^6个细胞产生超过480 pg的蛋白质。然而，肿瘤坏死因子-α处理产生了不同的结果。用肿瘤坏死因子-α刺激上皮细胞导致每个细胞出现超过560个GM-集落刺激因子mRNA分子，并产生超过1300 pg的GM-集落刺激因子/10^6个细胞。相比之下，刺激角膜成纤维细胞导致每个细胞产生少于16个GM-集落刺激因子mRNA分子和少于60 pg的GM-集落刺激因子/10^6个细胞。用125I标记的肿瘤坏死因子-α进行的结合研究表明，角膜成纤维细胞与角膜上皮细胞具有相同数量的受体位点。此外，角膜成纤维细胞能够对肿瘤坏死因子-α受体介导的信号转导作出反应，因为在用这种细胞因子处理后它们会产生纳克量的白细胞介素-6。结果表明，这两种细胞类型均响应白细胞介素-1α合成GM-集落刺激因子，但只有角膜上皮细胞在暴露于肿瘤坏死因子-α后产生大量的GM-集落刺激因子。这两种细胞类型对肿瘤坏死因子-α反应的差异可能反映了一种限制中性粒细胞和朗格汉斯细胞积累的方式，从而使角膜损伤最小化。
