A study on cell-mediated immunity in polymorphic light eruption.

Polymorphic light eruption (PLE) can be defined as a delayed abnormal response to sunlight. In this paper some features of the presumable immune response were studied in 55 patients with PLE and the results were compared with the findings available in 58 cases with porphyria cutanea tarda (PCT). The mean intracutaneous reactivity index measured by skin tests of delayed type was normal in both diseases. The number of the active and total E-rosette-forming peripheral lymphocytes was significantly lower in the active stage of PLE whereas in remission normal values were found. In active PCT only the number of the total E-rosette-forming cells was decreased. The percentage of lymphocytes with so-called dot-like alpha-naphthyl acetate esterase enzyme reaction was reduced significantly in the active stage of PLE whereas in remission their number was normal. Changes observed in PLE seem to be functional and suggest the involvement of T lymphocytes in some phases of the hypersensitive cutaneous reaction induced by sunlight.