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，这些突变可能会在许多年后发展为癌症。皮肤的免疫系统是防止大多数潜在癌细胞发展成皮肤肿瘤的重要防御系统。紫外线还会抑制皮肤免疫力，允许癌细胞不受控制地扩散。也有证据表明，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。阳光中含有会导致晒伤的UVB和UVA。直到最近，UVA还被认为对皮肤免疫力几乎没有影响。我们之前已经证明，宽带UVB和UVA都具有免疫抑制作用，即使在相当于8分钟阳光的单次照射后也是如此。目前尚不清楚哪些UVA波长的免疫抑制作用最强。这些研究将使用氙弧太阳模拟器和一系列干涉滤光片来产生窄的UVB和UVA波段。这些波段对人类的影响可以通过故意激发对志愿者已经敏感的物质的免疫反应来研究。在这些研究中，皮肤免疫的一个模型是镍过敏(在耳环和服装首饰中)，影响10%的女性。志愿者的背部被暴露在不同的紫外线波长下，然后镍贴片被贴在紫外线暴露的区域和邻近的未暴露的区域。通过比较这些镍反应的强度(红色和厚度)，可以测量到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中)提供了另一种皮肤免疫的补充模式。了解不同紫外线波长(紫外线免疫抑制的作用光谱)的免疫效果将提高对皮肤癌的理解，并使更好的防晒霜的开发成为可能，目前防晒霜只提供部分免疫保护。

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.