Modulation of cytokine production by 8-methoxypsoralen and UVA.

Modulatory effects on cytokine expression of 8-MOP in conjunction with UVA have been investigated in different systems using different cell types, including keratinocytes, lymphocytes, monocytes and endothelial cells. The vast majority of data have exhibited reduced production of cytokines in 8-MOP/UVA-treated cells and skin, reflecting its simplistic cellular damage. However, 8-MOP/UVA at modest doses stimulate T lymphocytes to produce Thl cytokines such as interferon-gamma, suggesting that some activational events may occur in certain types of cells phototreated with 8-MOP. Both the inhibitory and augmentative effects of 8-MOP/UVA on cytokine production appear to participate in the mechanisms underlying the therapeutic efficacy of PUVA and extracorporeal photochemotherapy (photopheresis). In particular, photopheresis may exert beneficial effects on cutaneous T-cell lymphoma as a cytokine modifier.