Lembo S, Fallon J, O'Kelly P, Murphy G M
Department of Dermatology, Beaumont Hospital, Dublin 9, Ireland.
Br J Dermatol. 2008 Dec;159(6):1342-7. doi: 10.1111/j.1365-2133.2008.08734.x. Epub 2008 Oct 14.
Ultraviolet (UV) radiation (UVR) interacts with chromophores in cutaneous cells with consequent antigenicity. The normal response to this is a downregulation of immune responsiveness. Failure of the immune system to downregulate and to ignore transient photoantigens in human skin results in polymorphic light eruption (PLE), the commonest of the photodermatoses. UVR initiates and promotes skin cancer (SC): UV-induced immunosuppression permits the expansion of UV-mutated clones of cells which ultimately lead to SC.
Because there is increased immune surveillance and resistance to immune suppression following UVR exposure in PLE one might expect a protective effect of PLE against SC and, conversely, a reduced risk of PLE among patients with SC.
We therefore constructed a prospective case-control study to see if this were the case. Two groups were studied: a group comprising 214 patients with SC and 210 gender- and aged-matched controls, and a group comprising 100 patients with PLE and 155 gender- and aged-matched controls. Each participant answered a questionnaire aimed at establishing personal and family history of SC and photodermatoses. Skin type and exposure to UVR were also documented.
The prevalence of PLE in people with SC was 7.5%, compared with 21.4% for controls (P<0.001). The prevalence of SC in patients with PLE was 4% compared with 7.1% for controls.
Our results show (i) strong evidence of reduced PLE in patients with SC, and (ii) a trend for reduced SC in patients with PLE. The immunological basis of PLE may therefore confer protection against SC.
紫外线（UVR）与皮肤细胞中的发色团相互作用，从而产生抗原性。对此的正常反应是免疫反应下调。人体皮肤免疫系统无法下调并忽略短暂的光抗原会导致多形性日光疹（PLE），这是最常见的光皮肤病。UVR引发并促进皮肤癌（SC）：紫外线诱导的免疫抑制使紫外线突变的细胞克隆得以扩增，最终导致皮肤癌。
由于PLE患者在UVR暴露后免疫监视增加且对免疫抑制有抵抗力，因此可能预期PLE对SC有保护作用，反之，SC患者发生PLE的风险降低。
因此，我们开展了一项前瞻性病例对照研究，以验证是否如此。研究了两组：一组包括214例SC患者和210例性别及年龄匹配的对照，另一组包括100例PLE患者和155例性别及年龄匹配的对照。每位参与者都回答了一份旨在确定SC和光皮肤病个人及家族史的问卷。还记录了皮肤类型和UVR暴露情况。
SC患者中PLE的患病率为7.5%，而对照组为21.4%（P<0.001）。PLE患者中SC的患病率为4%，而对照组为7.1%。
我们的结果表明：（i）有强有力的证据表明SC患者中PLE减少，（ii）PLE患者中SC有减少的趋势。因此，PLE的免疫学基础可能对SC有保护作用。
