Role of the polymorphonuclear neutrophils in the phototoxic reaction in porphyria cutanea tarda

We have compared the superoxide production of polymorphonuclear cells (PMNLs) from healthy donors, when incubated with either control or porphyria cutanea tarda (PCT) sera at 4, 24 and 48 hours after exposure in vivo to UVA light. Serum from UVA-irradiated (1-5 J/cm2) PCT patients generated significantly greater amounts of superoxides from PMNLs than serum from UVA-irradiated (8-12 J/cm2) normal controls. This indicates that serum factors activated by porphyrin plus UVA stimulate neutrophilic granulocytes to liberate superoxides, triggering a series of events that cause tissue damage. The vascular lesions in patients with PCT could be, at least in part, due to this cytotoxic effect.