Whole-body exposure to ultraviolet radiation results in increased serum interleukin-1 activity in humans.

Human volunteers given one minimal erythemal dose of ultraviolet radiation (UVR) from fluorescent sunlamps developed increased serum interleukin-1 (IL-1) activity as assessed by the thymocyte co-stimulator assay. This activity peaked 1 to 4 hours after exposure and returned to baseline by 8 hours after exposure. Six to 12 months later, some of the same subjects had blood samples taken over the same time course but without exposure to UVR; no elevation in serum IL-1 was observed. In addition to lymphocyte activating activity, IL-1 has been reported to have endogenous pyrogen activity, chemotactic activity for neutrophils and mononuclear cells, and inflammatory activity when injected subcutaneously in vivo. Elevations in serum IL-1 activity after exposure to ultraviolet radiation may account for some of the manifestations of the sunburn response.