Determination of an action spectrum for ultraviolet radiation-induced immunosuppression in humans

紫外线（UV）辐射会导致皮肤突变，多年后会发展成癌症。皮肤的免疫系统是一个重要的防御系统，可以防止大多数潜在的癌细胞发展成皮肤肿瘤。紫外线还会抑制皮肤免疫力，使癌细胞不受控制地增殖。还有证据表明，这种紫外线诱导的免疫抑制可能对疱疹病毒、麻风病和热带溃疡等传染病有重要影响。阳光中含有导致晒伤的中波紫外线和长波紫外线。直到最近，人们还认为长波紫外线对皮肤免疫力几乎没有影响。我们之前的研究表明，宽带UVB和UVA都有免疫抑制作用，即使是在一次相当于8分钟的阳光照射后也是如此。目前尚不清楚哪种长波长波最具免疫抑制作用。这些研究将使用氙弧太阳模拟器和一系列干涉滤光器来产生窄的中波和中波波段。这些波段对人体的影响可以通过故意引起志愿者对已经敏感的物质的免疫反应来研究。这些研究中的一种皮肤免疫模型是对镍（耳环和人造珠宝中的镍）过敏，10%的女性受到影响。志愿者的背部暴露在不同波长的紫外线下，然后在暴露在紫外线下的区域和邻近的未暴露的区域贴上镍片。通过比较这些镍反应的强度（红度和厚度），可以测量每个波段引起的免疫抑制。同样，曼图反应（在接种结核病疫苗的人群中）提供了另一种皮肤免疫的补充模型。了解不同紫外线波长（紫外线免疫抑制的作用光谱）的免疫作用将提高对皮肤癌的认识，并使开发更好的防晒霜成为可能，目前这些防晒霜只能提供部分免疫保护。

Ultraviolet (UV) radiation causes mutations in the skin which can develop into cancers many years later. The skin's immune system is an important defence that prevents most potentially cancerous cells from developing into skin tumours. UV also suppresses skin immunity, allowing cancer cells to proliferate unchecked. There is also evidence that this UV-induced immunosuppression may have important effects on infectious diseases such as herpes virus, leprosy and tropical ulcers. Sunlight contains UVB, which causes sunburn, and UVA. Until recently, UVA was thought to have little effect on skin immunity. We have previously shown that both broadband UVB and UVA are immunosuppressive, even after single exposures equivalent to 8 minutes of sunlight. It is not known which UVA wavelengths are most immunosuppressive. These studies will use a xenon arc solar simulator and a series of interference filters to produce narrow UVB and UVA wavebands. The effects of these wavebands on humans can be studied by deliberately eliciting immune responses to substances which volunteers are already sensitive to. One model of skin immunity in these studies is allergy to nickel (in earrings and costume jewellery), which affects 10% of women. The volunteers' backs are exposed to different UV wavelengths, and then nickel patches are taped to both the UV-exposed areas and adjacent, unexposed areas. By comparing the intensity (redness and thickness) of these nickel reactions, immunosuppression caused by each waveband can be measured. Similarly, the Mantoux reaction (in people vaccinated against tuberculosis) provides another, complementary model of skin immunity. Knowledge of the immune effects of different UV wavelengths (an action spectrum for UV immunosuppression) would improve understanding of skin cancer and enable development of better sunscreens, which currently offer only partial immune protection.