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 kefir-anofaciens MI and its supernatant had strong potential to induce in vitro production of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 beta, 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-alpha production. These findings indicated that kefir influenced the secretion of pro-inflammatory cytokines TNF-alpha 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. (C) 2008 Elsevier Ltd. All rights reserved.