Narrowband ultraviolet B radiation suppresses contact hypersensitivity

Summary Background/purpose: A main mechanism responsible for the efficacy of narrowband ultraviolet (UV)B is thought to be the induction of apoptosis in pathogenetically relevant cells. Narrowband UVB therapy, however, generally induces a relatively long remission period. Recently, evidence that UVB radiation induces regulatory T (Treg) cells was reported. Based on these findings, we examined whether narrowband UVB suppresses contact hypersensitivity (CHS) by inducing Treg cells. Methods: The shaved abdomens of C3H/HeN mice were irradiated with broadband or narrowband UVB. CHS was defined as an ear-swelling response. To examine whether tolerance can be induced by adoptive transfer, lymph node cells from UVB-irradiated mice were injected into naive mice before sensitization and CHS challenge. Results: Narrowband UVB exposure dose dependently suppressed CHS. Significant suppression was observed at doses between 1000 and 3000 mJ/cm2 (P<0.05). The suppressive effect achieved with 1000 mJ/cm2 narrowband UVB was very similar to the effect achieved with 100 mJ/cm2 broadband UVB. The suppressive effects on CHS were transferred to naive mice by the injection of lymph node cells from tolerant mice. Conclusion: Narrowband UVB induced local and systemic suppression of CHS. In addition, narrowband UVB induces tolerance to CHS and the suppressive effects were transferable to naive mice.