UVB/PUVA- Induced Suppression of Human Natural Killer Activity Is Reduced by Superoxide Dismutase and/or Interleukin 2 In Vitro

We have evaluated the effects of ultraviolet irradiation or PUVA treatment (8-methoxypsoralen (8-MOP) plus long-wave ultraviolet (UVA) irradiation] on natural killer (NK) activity of human peripheral blood mononuclear cells (PBMC). In vitro exposure of PBMC to UVB (280-320 nm, 1–30 mJ/cm2) or PUVA [8-MOP, 0.1 μg/mI; UVA (320–400 nm), 0.5–5 J/cm2] resulted in a dose-dependent suppression of NK activity, whereas UVA (0.5–5 J/cm2) or 8-MOP, (0.1 μg/ml) treatment alone did not have the inhibitory effects. This suppressive effect of UVB/PUVA irradiation was successfully reduced in the presence of superoxide dismutase (SOD) (100 or 1000 U/ml) during the irradiation. The addition of interleukin 2 (IL-2) (100 U/ml) markedly enhanced the NK activity of both irradiated and nonirradiated PBMC. Combination treatment with both SOD and IL-2 to UVB/PUVA-irradiated PBMC resulted in a more remarkable improvement of NK suppression than with either SOD or IL-2 treatment alone.