Moodycliffe A M, Kimber I, Norval M
Department of Medical Microbiology, University of Edinburgh Medical School, U.K.
Immunology. 1992 Nov;77(3):394-9.
Irradiation with ultraviolet-B light (UV-B) suppresses some cell-mediated immune responses to a variety of antigens, including contact sensitizers. Following UV irradiation there is modulation of Langerhans' cells' markers and keratinocytes are induced to synthesize and secrete tumour necrosis factor-alpha (TNF-alpha). Cis-urocanic acid (cis-UCA) has been suggested as a photoreceptor for UV and has been demonstrated to suppress immune responses in several experimental systems. UCA is found naturally in the stratum corneum as the trans-isomer and converts to the cis-isomer on irradiation. In the present study the migration of dendritic cells (DC) to lymph nodes following UV-B irradiation or epicutaneous application of UCA isomers was examined in unsensitized mice and mice sensitized with fluorescein isothiocyanate (FITC). It was found that UV-B irradiation alone induced DC migration to draining lymph nodes (DLN) and that UV-B irradiation prior to skin sensitization at the same site enhanced DC migration. A maximum number of DC was present in DLN 48 hr following irradiation. In sensitized mice, the percentage of DC bearing FITC and the quantity of FITC per DC was unaltered by prior UV exposure. In contrast, neither isomer of UCA had any significant effect on DC numbers in sensitized or unsensitized mice. It was concluded that UV-B irradiation induced the migration of DC from the epidermis to draining lymph nodes, an effect possibly mediated by TNF-alpha release, while UCA may act by a different mechanism, perhaps via histamine-like receptors in the epidermis.
紫外线B光（UV-B）照射可抑制对多种抗原（包括接触性致敏剂）的一些细胞介导的免疫反应。紫外线照射后，朗格汉斯细胞标志物会发生调节，角质形成细胞被诱导合成并分泌肿瘤坏死因子-α（TNF-α）。顺式尿刊酸（cis-UCA）被认为是紫外线的光感受器，并已在多个实验系统中被证明可抑制免疫反应。尿刊酸在角质层中天然以反式异构体形式存在，照射后会转化为顺式异构体。在本研究中，在未致敏小鼠和用异硫氰酸荧光素（FITC）致敏的小鼠中，检测了UV-B照射或经皮应用尿刊酸异构体后树突状细胞（DC）向淋巴结的迁移情况。发现单独的UV-B照射可诱导DC迁移至引流淋巴结（DLN），并且在同一部位进行皮肤致敏之前的UV-B照射可增强DC迁移。照射后48小时，DLN中存在最大数量的DC。在致敏小鼠中，预先暴露于紫外线对携带FITC的DC百分比和每个DC的FITC数量没有影响。相比之下，尿刊酸的两种异构体对致敏或未致敏小鼠的DC数量均无任何显著影响。得出的结论是，UV-B照射诱导DC从表皮迁移至引流淋巴结，这一效应可能由TNF-α释放介导，而尿刊酸可能通过不同机制起作用，也许是通过表皮中的组胺样受体。
