Suppression of delayed and contact hypersensitivity responses in mice have different UV dose responses

Although acute exposure to UV radiation suppresses the induction of delayed-type (DTH) and contact (CHS) hypersensitivity in mice, it is not clear whether the photobiological mechanism(s) involved in suppressing these closely related immune reactions is the same. A careful examination of the UV dose responses and wavelength dependencies involved in suppressing CHS and DTH may provide important insights into the mechanisms involved. We compared the UV dose-response curves for suppressing four closely related immune reactions, local and systemic suppression of CHS to dinitrofluorobenzene, systemic suppression of DTH to Candida albicans and systemic suppression of DTH to alloantigen using three different UV spectra (FS40 sunlamps, Kodacel-filtered FS40 sunlamps and solar-simulated light). For each immune response studied, the amount of UVB radiation required to induce 50% immune suppression was lowest when FS40 sunlamps were used, highest with solar-simulated light and intermediate when Kodacel-filtered FS40 sunlamps were used, but the differences observed were not statistically significant. The UV dose-response curves for immune suppression differed significantly depending on the assay used, the site of antigenic sensitization and the antigen used. These findings suggest that the mechanisms by which UV radiation induces immune suppression differ for the four immunological reactions studied.