Suppression of pathogenesis in cutaneous leishmaniasis by UV irradiation.

The effects of suberythematous levels of UV-B radiation on the development of of cutaneous leishmaniasis were studied in B10.129(10M) mice. Doses of 15 mJ cm-2 UV-B applied locally to the injection site suppressed the development of skin lesions after the inoculation of Leishmania major promastigotes. The primary targets of UV-B radiation appeared to be host cells and not leishmanial parasites, because UV-B irradiation of parasites cultured in vitro did not affect their viability, but did kill host cells. Furthermore, the same numbers of parasites were recovered from skin at the injection site in both irradiated and control mice. UV-B irradiation abrogated the induction of contact hypersensitivity to dinitrofluorobenzene and also abrogated the induction of delayed-type hypersensitivity responses to leishmanial antigens. These results suggest that local perturbations in the functions of the skin-associated lymphoid tissue during the initial phases of leishmanial infection can profoundly influence immunological response and the subsequent development of clinical disease.