Activation of complement in the skin after PUVA therapy.

Suction blister fluid from the abdominal skin of 14 healthy subjects was examined for the presence of split products of complement C3 (C3-split) as an indicator of complement activation before and after treatment with either UVA or PUVA. Following PUVA a significant increase in C3-split was found (p less than 0.05) in both irradiated and non-irradiated skin areas. Following UVA the increase in C3-split was less pronounced. The activation of complement may play an important role in the maintenance of the delayed erythema that appears after irradiation with long-wave ultraviolet light.