CONICET | Buscador de Institutos y Recursos Humanos

The knowledge about the relationship between non-pathogenic bacteria (probiotics) and the host and their influences in the activation of the intestinal mucosal immune system (IMIS) are not well understood yet. We study the mechanism involved in the immunomodulation by probiotics in BALB/c mice in order to know how the probiotic bacteria induce immunoestimulation L. casei, L. acidophilus and L. delbrueckii subsp. bulgaricus were used. We analyzed adhesion, internalization and persistence in the gut by using immunofluorescence (IF) technique and transmission electronic microscopy (TEM). Then, we study the influence of the probiotic bacteria interaction in the activation/suppression of intestinal immune system: number of IgA+, TNFa +, IL-2+, IL-4+, IL-10+ cells by IFI on intestinal histological slices. We also analyzed the influence of viability in the immunoestimulation of the IMIS (IgA+ cells and cytokines) after the administration of viable or heat-dead lactic acid bacteria. The effect of the administration prolonged on the IMIS was also evaluated. By TEM, we demonstrated that the whole bacteria were able to interact with the microvilli of the epithelial cells and the antigenic fragments are internalized and uptake by the immune cells. The kinetic of antigenic depuration was similar to the one observed for a particulate antigen (72h). The antigenic contact with the immune cells induced an increase in the number of IgA+ cells and the production of proinflammatory and regulatory cytokines. The viability of probiotics warrants a good activation of the IMIS. The long term of probiotics administration, did not induce secondary effects. We demonstrated that the immunomodulating properties of lactic acid bacteria were characteristics of each strain and they can not be extrapolated to the bacterial genera or species.

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