Lactobacillus johnsonii JERA01 upregulates the production of Th1 cytokines and modulates dendritic cells-mediated immune response

Lactic acid bacteria are known to have various effects on the immune system. The type and extent of the effect differ, depending on the type of lactic acid bacteria. This study aimed to investigate the effects of Lactobacillus johnsonii bacterin on mouse-derived immune cells. Treating splenocytes with L. johnsonii bacterin slightly increased the metabolic activity. Additionally, the expression of the activation marker CD25 and production of the Th1-type inflammatory cytokine interferon (IFN)- gamma increased. We confirmed that the increase in IFN-gamma production due to L. johnsonii stimulation was mainly due to T and B cells among splenocytes. Treating dendritic cells (DCs) with L. johnsonii bacterin at concentrations of 10⁶ and 10⁷ cfu/ ml significantly increased tumor necrosis factor-alpha, a pro-inflammatory cytokine, and interleukin-12, a cell-mediated immunity cytokine. Additionally, the expression of surface markers increased. Allogeneic mixed lymphocyte reactions showed that L. johnsonii reduced the antigen-presenting ability of DCs. In cocultures of DCs and splenocytes, L. johnsonii decreased cellular metabolic activity and increased cell death. L. johnsonii upregulated the expression of programmed death ligand 1 on DCs. The findings of this study indicate that L. johnsonii bacterin has immunomodulatory and immunostimulatory effects. While L. johnsonii increased the expression of cytokines and surface markers of immune cells, it modulated DC-mediated immune response. Further studies are needed to determine the effects of L. johnsonii bacterin on DCs and related immune cells.