MECHANISMS INVOLVED IN IMMUNE STIMULATION BY LACTIC ACID BACTERIA AND YOGURT

PERDIGÓN, G.; MEDINA, M.; RACHID, M.; MEDICI, M.; MARIA CAROLINA MALDONADO GALDEANO; DE MORENO DE LEBLANC, A

MEXICO

Simposio; Simposio DANONE de México; 2001

In previous work we determined that some lactic acid bacteria (LAB) (eg. Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus) induced different mucosal immune responses (specific, non specific or both).We proposed that such behaviour was due to the different sites of interaction of the LAB with the gut. We showed that: a) the bacteria were present in different part of the intestine, b) the pathway of internalization of the strains used, to make contact with the immune system were through: M cell or FAE cell from Peyer’s patches and epithelial cells of small or large intestine. These findings could explain the diversity of mucosal immune response induced. The above results led us to analyze the cytokines that the LAB were able to release. We found that the LAB were able to induce a diversity of responses mediated by the cytokines released. We could not established different properties in the immunostimulation for each LAB assayed. We think the results were due to the use of heterologous strains, of different origins; some of them from human tested in a mouse model. Thus we compared the behaviour of Bifidobacterium sp. and Lactobacillus animalis (isolated from mouse) with the corresponding human heterologous strains. We demonstrated, that host specificity is important for the genus Bifidobacterium, but not for lactobacilli. When we studied the mechanisms by which yogurt was able to inhibit the growth of a chemically induced intestinal tumour, we demonstrated that yogurt can down regulate the inflammatory response induced by the carcinogen by: 1) increase of IgA+ cells and CD4+ T cells, 2) increase of cellular apoptosis, 3) the apoptosis was favoured by an increase in the levels of TNFa release, induced by yogurt and 5) yogurt induce IL10 release which plays an important role in the mechanisms of down regulation. We concluded that the mechanisms involved in the immunostimulation by LAB or yogurt are multiple and these finding indicate that will be very difficult to establish a reliable test for selection of LAB with immunostimulatory capacity. However, the knowledge of the mechanisms controlling the response to an individual strain or yogurt, will allow a better choice for therapeutic purposes.