1158 UVC irradiation induces neuropilin-1+ regulatory T cells in skin and lymph nodes

UV light is an immune system regulator. In a mouse model of contact hypersensitivity, UV irradiation causes immune tolerance in an antigen-specific manner by inducing regulatory T cells (Tregs). Expanded Tregs are observed in UVB-irradiated skin and draining lymph nodes. The best conditions to induce UV-expanded Tregs (UV-Tregs) are unknown. We focused on UVC to UVB wavelengths to investigate UV-Tregs induction and identify changes in functional gene expression. The minimal erythema dose (MED) of each wavelength was determined. RNA sequencing (RNA-seq) analysis of CD4+ T cells from lymph nodes on day 7 after 3MED of 260, 280, and 300nm irradiation revealed a 2-fold upregulation of IL-10 compared with sham irradiation. CCL22, which enhances the migratory activity of CCR4+ cells including Tregs, was upregulated 3-fold by UV irradiation. Nr4a1-3 mRNA levels, associated with T cell tolerance, increased 3-fold in the same specimens after UV irradiation compared with sham-irradiation. Non-negative matrix factorization applied to the RNA-seq data showed that CD4+ “Tregness” was increased by 3MED of 260, 280, and 300nm UV irradiation. Flow cytometry analysis showed that Helios+ and Neuropilin-1+ Tregs increased at 260nm compared with other wavelengths. These data suggest that a 260nm wavelength (UVC) facilitates UV-Tregs induction. UV-Tregs formed clusters with dendritic cells (DCs) and proliferated in situ. DCs expand UV-Tregs. DC clusters were observed with Tregs at 240–260nm (UVC). At 240, 260, 280, and 300nm on days 3 and 7 after UV irradiation, the numbers of Foxp3+ CD4+cells/5 different high-power fields (HPF) was 6, 9, 1, and 2, and 7, 4, 4, and 5, respectively. These data suggest that UVC irradiation expands UV-Treg induction with DC stimulation.