Ultraviolet B–Induced Maturation of CD11b-Type Langerin− Dendritic Cells Controls the Expansion of Foxp3+ Regulatory T Cells in the Skin

Skin dendritic cells (DCs) are divided into several subsets with distinctive functions. This study shows a previously unappreciated role of dermal CD11b-type Langerin− DCs in maintaining immunological self-tolerance after UVB exposure. After UVB exposure, dermal CD11b-type Langerin− DCs upregulated surface CD86 expression, induced proliferation of Foxp3+ regulatory T (Treg) cells without exogenous Ags, and upregulated a set of genes associated with immunological tolerance. This Treg-expansion activity was significantly hampered by CD80/CD86 blockade in vivo. These results indicate that CD11b-type Langerin− DCs from the UVB-exposed skin are specialized to expand Treg cells in the skin, which suppress autoimmunity.