Effects of whole-body UVB irradiation on cytokine production by peripheral blood mononuclear cells from stage I melanoma patients

Ultraviolet (UV) radiation causes significant impairment of immunological function in human skin. The immunosuppressive effects of UV radiation are thought to be due to local release of cytokines by human keratinocytes, leading to impaired function of epidermal antigen-presenting cells (APC) and failure to induce cutaneous delayed-type hypersensitivity (DTH) reactions. Recent studies have shown that individuals susceptible to UV-induced suppression of DTH may be more prone to develop skin cancer including malignant melanoma (MM). Since the causal relationship between UV radiation and the induction of MM still seems obscure, we investigated the immunological reactions of peripheral blood mononuclear cells (PBMC) to whole-body irradiation with UVB in 15 stage I melanoma patients as compared to PBMC from normal volunteers matched for age, gender and skin type. Whole-body irradiation was performed with 0.8 minimal erythema dosages on five consecutive days. Peripheral blood was obtained before and after the procedure. Overall, there were no major effects of UVB irradiation on peripheral lymphocyte subsets and proliferation of PBMC from patients or normal controls, but UVB irradiation led to a significant increase in PWM-stimulated production of IL-6, IL-2R and TNF by PBMC. These changes were independent of the individual UVB dosages administered and appeared in both groups similarly. UVB irradiation did not lead to significant changes on IL-1 and IL-2 expression by PBMC. Our results suggest that PBMC participate in the cytokine response to UV, even in the absence of inflammatory reactions, but that this participation is not specific to MM patients.