In vivo evidence that ultraviolet B-induced suppression of allergic contact sensitivity is associated with functional inactivation of Th1 cells

Having previously shown in vitro that ultraviolet B (UVB)-treated Langerhans cells (LC) can induce antigen-specific proliferative unresponsiveness and tolerance in Th1 (but not Th2) cells, we wanted to determine whether cutaneous exposure to UVB radiation prior to hapten-painting would produce similar differential effects in hapten-reactive Th1 and Th2 T cells in vivo. C3H/HeN mice were exposed to UVB (200 J/m²/day) through abdominal skin on days -4 through -1, followed by painting dinitrofluorobenzene (DNFB) on the irradiated skin on days -1 and 0. Induction of allergic contact sensitivity (CS) was assayed by ear swelling responses to DNFB and by the proliferative responses of draining lymph node cells (LNC) to DNBS. UVB-irradiated and hapten-painted mice (in comparison to a control panel of unirradiated and DNFB-painted mice) displayed suppressed ear swelling responses to DNFB and suppressed LNC proliferation to DNBS, However, LNC from either panel of mice proliferated well in response to exogenous interleukin 2 (IL-2). To examine effects on Th1 and Th2 cells, lymphokines were assayed from supernatants of DNBS-stimulated LNC. The Th1-associated lymphokines, interferon-γ and IL-2, were the predominant cytokines detected in samples taken from unirradiated and DNFB-painted mice. Both of these cytokines were reduced markedly in samples from UVB-treated and DNFB-painted mice. Except for miniscule amounts of IL-10, no Th2-associated lymphokines were detected in LNC supernatants from either panel of mice. These results suggest that UVB-induced suppression of CS in vivo is associated with functional inactivation of hapten-reactive Th1 cells.