The intestinal ecosystem is a very complex network of interactions between prokaryotic ? eukaryotic or eukaryotic ?
eukaryotic cells. In this microenvironment coexist in a perfect equilibrium, a large number of bacteria (1010-1011g/feces)
and the immune cells associated to the mucosa responsible of the mucosal immune response. This microbiota is very stable and
avoids the colonization of pathogenic bacteria (barrier effect) Probiotics bacteria and functional food can influence not only the
microbiota, favoring the growth of beneficial microorganisms, but also the mucosal immune system associated to the gut.
The improvement of the immune status of the host is one of the beneficial properties attributed to the probiotics. Previous
results in our laboratory using mouse as experimental model, showed that the effect induced by a probiotic strain Lactobacillus
casei CRL 431was through the innate immunity. This bacterium is able to interact with the epithelial and immune cells, increase
IgA secreting cells, cytokines and receptors as CD206 and TLR2 These Studies were performed comparatively with commensal
We determined the effect of non pathogenic Gram (+), bacteria and a Gram(+) probiotic strain on the inductor site (PP) and
effector site (lamina propria) of the intestine.We demonstrated that commensal bacteria were able to induce an immunostimulation
less than those obtained with probiotic bacteria and that the lipoteichoic acid (LTA) is not the only structure implicated in the
To understand these differences observed in the gut: we analyzed comparatively the signals induced by probiotic and
commensal bacteria to activate the transcriptional factors NFAT (through the calcineurine enzyme), NFkB and TLR-9. Both
probiotic and commensal bacteria activated the NFAT, but TLR9 was only increased by probiotic and NFkB was more activated
by probiotic than commensal bacteria. Increases of co-stimulatory molecules expression by probiotic administration were also
observed. We studied the importance in the signals induced through TLRs in knockout animals for TLRs. We demonstrated that
the main metabolic via of signal for probiotics to activate the Immune System is through TLR, different to commensal bacteria
that induce a slight stimulation for this way.
Conclusions: Probiotics and commensal bacteria activate NFkB to promote the production of certain cytokines, as well as.NFAT
and TLR9 to stimulate the mucosal response., however the level of activation was more effective for probiotic than commensal
bacteria.The most important via of signals used by probiotic is from TLRs.
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