051 Dermal dendritic cells present neo-self antigens induced by ultraviolet B exposure to expand Foxp3+ regulatory T cells

Abstract

Dendritic cells play a key role in controlling homeostasis Foxp3+ regulatory T cells (Tregs), which constitute about 5-10% of peripheral CD4+T cells. The literature showed that Tregs contributed to immunosuppression induced by ultraviolet B (UVB) exposure using contact hypersensitivity models. Here we found that Tregs were expanded to more than half of CD4+T cells in the murine skin after UVB exposure without hapten-application. Upon UVB exposure, Tregs actively proliferated via interacting with dermal dendritic cells in the absence of exogenous antigen in vivo. Moreover, Treg proliferation were stimulated by a subset of dermal dendritic cells from UVB-exposed skin without exogenous antigen in vitro, indicating that neo-self antigens induced by UVB exposure are presented by the dendritic cell subset. RNA sequencing analysis showed that the dermal dendritic cell subset highly expressed immunological tolerance related genes such as Areg, Tnfsf9, and PD-L1. UVB-expanded Tregs in the skin also contributed to the homeostasis of Tregs in systemic lymphoid organs. These results suggest that immunological self-tolerance is regulated by Tregs expanded by a special subset of dendritic cells presenting neo-self antigens induced by UVB exposure.