Effects of kefir supernatant and lactic acid bacteria isolated from kefir grain on cytokine production by macrophage

The objective of this study was to investigate the in vitro immuno-modulating capacity and mechanisms of lactic acid bacteria (LAB) isolated from kefir grains and their individual supernatants by cytokine profiles through a toll-like receptor pathway. Results demonstrated that kefir supernatants, obtained from kefir fermented more than 24 h, induced the production of pro-inflammatory cytokines in RAW 264.7 cells. Among four LAB isolated from kefir grains and their supernatants, Lactobacillus kefiranofaciens M1 and its supernatant had strong potential to induce in vitro production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and IL-12 in RAW 264.7 cells and murine peritoneal macrophages. Moreover, blocking toll-like receptor (TLR)-2 using anti-TLR-2 mAb and TLR-2−/− mice showed a significant inhibition (p < 0.05) of IL-6 and TNF-α production. These findings indicated that kefir influenced the secretion of pro-inflammatory cytokines TNF-α and IL-6 through TLR-2, which would potentially have beneficial effects on promotion of cell-mediated immune responses against tumors and also against intracellular pathogenic infections. The putative immunomodulin in the kefir supernatant was also characterized and may be a protein with a molecular mass larger than 30 kDa.