CD4+ T cells in lymph nodes of UVB-irradiated mice suppress immune responses to new antigens both in vitro and in vivo

Abstract

The mechanisms by which erythemal UVB irradiation modulates systemic immune responses to antigens applied to non-irradiated sites are poorly understood. In this study, regulatory CD4+ T cells were identified in the skin-draining lymph nodes (SDLNs) of UVB-irradiated, but otherwise naive mice. A transgenic mouse strain (DO11.10) was utilized in which the majority of CD4+ T cells expressed the ovalbumin (OVA(323-339)) T-cell receptor. Thus, T-cell responses could be examined following erythemal UVB irradiation without further antigen sensitization. CD4+ T cells from the SDLNs of UVB-irradiated mice had significantly reduced capacity to respond to presentation of the OVA(323-339) peptide in vitro. Transfer of CD4+ T cells from the SDLNs of UVB-irradiated antigen-naive mice significantly reduced both OVA sensitization and contact hypersensitivity responses to an experimental hapten in the recipient mice. Depletion of CD4+CD25+ cells abrogated this UVB-suppressive effect in the in vitro proliferation assay. There was also a significant increase in the proportion of CD4+CD25+Foxp3+ cells in the SDLNs of UVB-irradiated mice. The potential of these regulatory cells poised to regulate responses to incoming antigens at distant non-irradiated sites broadens the biological impact of UVB irradiation of skin on immunity.