Regulatory B cells induced by ultraviolet B through toll-like receptor 4 signalling contribute to the suppression of contact hypersensitivity responses in mice.

BACKGROUND: Ultraviolet (UV) B irradiation is known to suppress contact hypersensitivity (CHS) responses in mouse models by suppressing immune responses. However, the cellular mechanisms responsible for UVB-induced systemic suppression remain unclear. Regulatory B cells have been reported to play an inhibitory role during CHS. It is presently unknown whether regulatory B cells contribute to the effect of UVB phototherapy.

OBJECTIVE: To investigate the inductive effect of UVB on regulatory B cells and the underlying mechanisms by using a CHS mouse model.

METHODS: CHS was induced with oxazolone, and evaluated by histopathology, flow cytometry, and quantitative real-time polymerase chain reaction.

RESULT: We found that UVB irradiation induced regulatory B cell expansion and ameliorated CHS. UVB-induced regulatory B cells contribute to systemic immunosuppression by inhibiting the proliferation of T cells. Moreover, we determined that toll-like receptor (TLR) 4, the expression of which was upregulated in B cells after UVB exposure, played an essential role in the induction of regulatory B cells.

CONCLUSION: Our data identified regulatory B cells as regulators of UVB-induced immunosuppression in CHS, and suggest the importance of the UVB-TLR4 axis in the generation of regulatory B cells.