Exposure to low-dose ultraviolet radiation suppresses delayed-type hypersensitivity to herpes simplex virus in mice

Ultraviolet B (UVB) radiation is reported to induce a defect in epidermal antigen presentation which leads to specific suppression of the delayed-type hypersensitivity (DTH) response to trinitrochlorobenzene. We have used a similar system to examine the murine DTH response to herpes simplex virus type 1 (HSV-1). Mice irradiated with 96 mJ/cm2 UVB on shaved dorsal skin 3 days before s.c. injection of live HSV-1 in the flank showed 54-92% suppressed DTH responses to challenge with inactivated virus compared with nonirradiated control animals. If irradiation took place 7 days before inoculation with virus, some suppression of DTH occurred; if 14 days before, no suppression was found. The transient nature of the UVB response is further illustrated by the observation that irradiation with the same dose of UVB 5 h before, or 3 days after, inoculation with virus had no effect on DTH. Once induced, some degree of UVB suppression was found to persist for at least 3 months after irradiation.