Elevated plasma interleukin-1 levels in humans following ultraviolet light therapy for psoriasis

Interleukin-1 (IL-1) is a potent cytokine with a wide range of biologic activities including induction of several acute phase responses. Ultraviolet radiation (UVR) is widely used as a therapeutic modality to treat many chronic skin diseases, including psoriasis. In the present study, we investigated whether ultraviolet B (UVB) radiation induced circulating IL-1 in the plasma of patients undergoing chronic UVB therapy. In order to remove plasma proteins which inhibit IL-1-induced T-cell proliferation, each plasma sample was chromatographed and each fraction was assayed for IL-1 activity. There was no detectable IL-1 before and 1 h after UVB radiation; IL-1 appeared 4 h after treatment and was absent after 24 h. Plasma IL-1 was neutralized by antibodies to recombinant human IL-1 beta and alpha. The anti-IL-1 alpha, but not anti-IL-1 beta, antibodies partially neutralized the IL-1 activity present in a keratinocyte cell line supernate. These results demonstrate that UVB therapy induces circulating IL-1 and that this IL-1 may originate from both keratinocyte and non-keratinocyte sources.