Immunomodulating capacity of kefir

Abstract

Kefir is a fermented milk produced by the action of lactic acid bacteria, yeasts and acetic acid bacteria, trapped in a complex matrix of polysaccharides and proteins. Beyond its inherent high nutritional value as a source of proteins and calcium, kefir has a long tradition of being regarded as good for health in countries where it is a staple in the diet. However, published human or animal feeding trials to substantiate this view are not numerous. The aim of this work was to determine the immunomodulating capacity of kefir on the intestinal mucosal immune response in mice and to demonstrate the importance of dose and cell viability on this response. BALB/c mice were fed with commercial kefir ad libitum (diluted 1/10, 1/50, 1/100 or 1/200) or pasteurized kefir (diluted 1/6, 1/10, 1/50, 1/100) for 2, 5 or 7 consecutive days. At the end of each feeding period, the bacterial translocation assay was performed in the liver. Small intestine structure was studied by haematoxilin-eosin staining and light microscopy. The number of IgA+ and IgG+ cells was also determined. For the functional doses chosen, cytokines (IL-2, IL-4, IL-6, IL-10, IL-12, TNF-α and IFN-γ) were determined. Kefir and pasteurized kefir were able to modulate the mucosal immune system in a dose-dependent manner. Kefir was administred 10-times more diluted than pasteurized kefir, but it induced an immunomodulation of similar magnitude, indicating the importance of cell viabilty. The results suggest that a Th1 response was controlled by Th2 cytokines induced by kefir feeding. Pasteurized kefir would induce both Th2 and Th1 responses. This is the first study in vivo regarding the mechanisms involved in the immunomodulating capacity of the oral administration of kefir containing viable or heat-inactivated bacteria at different doses.

Distal Mucosal Site Stimulation by Kefir and Duration of the Immune Response

“…In this study, a significant increase in the number of IgG+ cells was observed in mice consuming pasteuri zed kefir. This increase in intestinal IgG had no detrimental effects in the gut, since no tissue damage or alteration of int estinal structures had been observed, as revealed by previous haematoxilineosin studies (22). Macrophages are considered the first line of defen se in the immun e response to foreign invaders.…”

“…Kefir containing viable bacteria was able to achieve a similar effect on the number of IgA+ cells as did pasteurize d kefir, even though the former had been admnistered lO times less concentrated than the latter. According to the number of IgA+ and IgG+ cells in the small intestine lamina propria and to haematoxi lin-eosin studies , 2 days of feeding with kefir diluted 1/100 and 5 days of feeding with pasteurized kefir diluted 1/10 were the conditions able to best modulate the intestinal mucosal immune reponse (22). The main function of secretory IgA in the gut is to exert immune exclusion by intimate cooperation with the innate non-specific defence mechanisms.…”

“…Mice were maintained and treated in accordance with the guidelines of the Canadian Council on Animal Care. Animals were offered kefir or pasteurized kefir at the conditions recently determined as functional (22). Kefir was offered diluted 1/100 and ad libitum for 2 consecutive days, whereas pasteurized kefir was diluted 1/10 and offered for 5 consecutive days (as a replacement for water) (22).…”

“…Animals were offered kefir or pasteurized kefir at the conditions recently determined as functional (22). Kefir was offered diluted 1/100 and ad libitum for 2 consecutive days, whereas pasteurized kefir was diluted 1/10 and offered for 5 consecutive days (as a replacement for water) (22). Kefir dilutions were done in Phosphate Buffered Saline (PBS) solution (Sigma-Aldrich, St. Louis, MO, U.S.A.).…”

“…Studies have been published concerning non-immune (12)(13)(14)(15)(16)(17) and immune system-related (18-21) effects of kefir. In a recent work (22) we performed a comparative study on the effect of kefir containing viable or non-viable bacteria by studying its modulatory activity on the intestinal immune response. A functional dose was established in a murine model, and the patterns of regulatory and pro-inflammatory cytokines induced were also studied.…”