[The effects of UVA irradiation on human neutrophil function]

We investigated the in vitro effects of ultraviolet A (UVA) irradiation on human neutrophil function. For measurements of reactive oxygen species (ROS) and serum opsonic activity, chemiluminescence was used. Chemotactic activity was determined by the Boyden technique. In this study, for detection of the effects of UVA irradiation on human neutrophil ROS production, we used luminol-dependent and lucigenin-dependent chemiluminescence, in addition to two kinds of action stimuli, opsonized zymosan and phorbol myristate acetate (PMA). We found that UVA irradiation at low doses of UVA (0.2-0.4J/cm2) did not affect the generation of OC1-, and it was suggested that high doses of UVA (0.6-1.0J/cm2) suppressed OC1- production by inactivating the signalling cascade which induces ROS on the membrane surface of neutrophils. No significant difference was observed in the chemotactic activity. The serum opsonic activity was increased by UVA irradiation. These results suggest that low doses of UVA do not impair neutrophil phagocytic activity, and that higher doses of UVA suppress the ROS generating capacity of neutrophils. However, to compensate for ths suppression, serum opsonic activity was induced, so it seemed that the neutrophil-related immune system could be retained.