Local effects of UV radiation on immunization with contact sensitizers. I. Down-regulation of contact hypersensitivity by application of TNCB to UV-irradiated skin.

Exposure of mouse skin to UV radiation in doses comparable to those commonly received by humans has been shown to diminish the capacity of irradiated skin to mediate the induction of contact hypersensitivity to dinitrofluorobenzene (DNFB). In other studies, contact sensitization reactions to the structurally related hapten, trinitrochlorobenzene (TNCB), have been used to test the immunogenic properties of haptenated subpopulations of epidermal cells. To extend the applicability of TNCB to experiments that examine UVB modulation of immunization by epidermal cells, we examined the sensitivity of TNCB-induced contact hypersensitivity to low doses of UVB radiation. Abdominal skin of C3H mice was exposed to daily doses of 660 J/m2 broad-band UV radiation for 4 successive days. Immediately following the final exposure, 7% TNCB was applied to irradiated or non-irradiated skin of designated mice. After 5 days, mice were ear-challenged with 2% TNCB, and incremental ear-swelling responses were measured. Mice sensitized with TNCB through irradiated skin exhibited significantly diminished responses compared with UVB-treated mice sensitized through non-irradiated skin. We also found that mice initially sensitized with TNCB through irradiated skin but subsequently painted with oxazolone on normal skin developed full responses to ear-challenge with oxazolone. In contrast, mice sensitized initially with TNCB through irradiated skin failed to fully immunize even after TNCB was repainted on normal skin at a later date. We conclude that low-dose UVB radiation interrupts the induction of contact hypersensitivity to TNCB, leading to hapten-specific nonresponsiveness rather than hypersensitivity, and that this capacity to prevent successful immunization with TNCB is limited to the site of irradiation.(ABSTRACT TRUNCATED AT 250 WORDS)