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 Lang erhans cells (LC) can induce antigen-specific proliferative unresponsi veness and tolerance in Th1 (but not Th2) cells, we wanted to determin e 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/m(2)/day ) through abdominal skin on days -4 through -1, followed by painting d initrofluorobenzene (DNFB) on the irradiated skin on days -1 and 0. In duction of allergic contact sensitivity (CS) was assayed by ear swelli ng responses to DNFB and by the proliferative responses of draining ly mph 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 L NC proliferation to DNBS. However, LNC from either panel of mice proli ferated well in response to exogenous interleukin 2 (IL-2). To examine effects on Th1 and Th2 cells, lymphokines were assayed from supernata nts of DNBS-stimulated LNC. The Th1-associated lymphokines, interferon -gamma and IL-2, were the predominant cytokines detected in samples ta ken from unirradiated and DNFB-painted mice. Both of these cytokines w ere 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 re sults suggest that UVB-induced suppression of CS in vivo is associated with functional inactivation of hapten-reactive Th1 cells.