ULTRAVIOLET-RADIATION INDUCED SUPPRESSION OF MANTOUX REACTIONS IN HUMANS

The effects of low dose ultraviolet (UV) radiation on delayed type hyp ersensitivity responses to tuberculin purified protein derivative were investigated in 17 healthy, Mantoux-positive volunteers. Suberythemal and erythemal doses of solar simulated UV from a fluorescent lamp sou rce were delivered to the subjects' lower backs daily for five consecu tive days. Mantoux testing with intradermally injected purified protei n derivative was then performed at both the irradiated sites and an ad jacent, unirradiated site, and the Mantoux induced erythema was quanti tated 72 h later with a reflectance erythema meter. In comparison with the unirradiated Mantoux sites, Mantoux induced erythema was signific antly reduced at the irradiated test sites. In six subjects, we compar ed the effects of chronic versus short term UV irradiation on the Mant oux reaction. These volunteers were irradiated on one side of their lo wer backs with the 5 d UV protocol, and on the other side of their bac ks for 4 or 5 wk. In all but one subject, the short irradiation protoc ol induced greater suppression of Mantoux responses than prolonged UV exposure. We conclude that even suberythemal doses of UV significantly reduce delayed type hypersensitivity responses to purified protein de rivative, and that an adaptive mechanism appears to counteract the imm unosuppressive effects of chronic irradiation.