Ligation of TLR7 on CD19+CD1dhi Bcells suppresses allergic lung inflammation via regulatory T cells

Bcells have been described as having the capacity to regulate cellular immune responses and suppress inflammatory processes. One such regulatory B-cell population is defined as IL-10-producing CD19(+)CD1d(hi) cells. Previous work has identified an expansion of these cells in mice infected with the helminth, Schistosoma mansoni. Here, microarray analysis of CD19(+)CD1d(hi) Bcells from mice infected with S. mansoni demonstrated significantly increased Tlr7 expression, while CD19(+)CD1d(hi) Bcells from uninfected mice also demonstrated elevated Tlr7 expression. Using IL-10 reporter, Il10(-/-) and Tlr7(-/-) mice, we formally demonstrate that TLR7 ligation of CD19(+)CD1d(hi) Bcells increases their capacity to produce IL-10. In a mouse model of allergic lung inflammation, the adoptive transfer of TLR7-elicited CD19(+)CD1d(hi) Bcells reduced airway inflammation and associated airway hyperresponsiveness. Using DEREG mice to deplete FoxP3(+) T regulatory cells in allergen-sensitized mice, we show that that TLR7-elicited CD19(+)CD1d(hi) Bcells suppress airway hyperresponsiveness via a T regulatory cell dependent mechanism. These studies identify that TLR7 stimulation leads to the expansion of IL-10-producing CD19(+)CD1d(hi) Bcells, which can suppress allergic lung inflammation via T regulatory cells.