Interferon-β Induced by Double-Stranded RNA of Lactic Acid Bacteria Promotes Differentiation of IFN-γ-Producing Th1 Cells

Double-stranded RNA of lactic acid bacteria (LAB) is recognized by dendritic cells (DCs) via endosomal TLR3 and benefits the anti-inflammatory response through induction of interferon-β (IFN-β). However, how such IFN-β impacts T cell immune responses, and how immune homeostasis is better maintained in the presence of commensal or food-derived LAB is unknown. Here we show that LAB enhances interleukin-12 (IL-12) secretion by DCs and differentiation of IFN-γ-producing T cells in an IFN-β-dependent manner. We demonstrated that IFN-β secreted in response to LAB increased IFN regulatory factor 1 (IRF1) and IRF7 mRNA, which contribute to Il12p35 expression. The resultant induction of Tbet and IFN-β in CD4⁺ T cells also occurs in vivo, where oral administration of LAB augments Th1 immune responses via TLR3 signaling pathway. Th1 induction due to TLR3-mediated IFN-β production may thus confer anti-allergic or anti-inflammatory activity by commensal or probiotic LAB.