Systemic immune response, probiotics

A critical criterion of selection is that the probiotic strain must be tolerated by the immune system and should not provoke the formation of antibodies against the probiotic. This latter property, in conjunction with the ability of some LAB to survive and colonize in the gut, has given rise to further applications, which involve their use as live vectors for oral immunization, i.e., introducing antigens targeting the GALT and aiming to induce a mucosal immune response (Marteau and Rambaud, 1993). 

Certain probiotic strains have been shown to stimulate the immune system in a beneficial, non-inflammatory manner. Such strains have also been shown to relieve the symptoms of allergic conditions such as atopic eczema and bovine milk protein intolerance in human feeding studies. The mechanisms underlying such beneficial modulation of immune response have not yet been fully elucidated. 

Although L. lactis represents a promising candidate for a live mucosal vector delivery system, some laboratories have further explored the capacity of other bacteria with better intrinsic propaties such as lactobacilli. Specific strains of lactobacilli have been characterized to possess probiotic properties (microorganisms that provide health benefits when consumed). Furthermore, some lactobaciUi species such as Lact. casei, Lact. acidophilus, Lact. gasseri, Lact. plantarum, and Lact. fermentum are able to persist for longer periods than L lactis in the GIT. Additionally, some species of lactobacilli are part of the microbiota that colonized the mammalian small intestine. The interaction of lactobacilli with the intestinal mucosa is an important factor because this enhances mucosal immune responses. Since the end of the 1990s, researchers have been exploiting these inherent properties of lactobacilli to make them an attractive alternative and safer delivery system for molecules and compounds with health benefit (Rush et al. 1995 Pouwels et al. 1996). 

There is increasing evidence that the interaction between the intestinal microbiota and the intestinal epithelial and immune cells plays a key role in the postnatal development of the immune system. First studies with probiotics (74) and synbio-tics (40) demonstrate effects during infancy, and studies regarding the vaccination response in the elderly (75) indicate that the prebiotics might also influence the immune system. In particular, the animal experiments with prebiotics described above allow the hypothesis that prebiotics that are able to influence the composition of the entire intestinal microbiota toward microbiota found in breastfed infants might support the development of the immune system during infancy. 

There are many scientific evidences, supported by clinical studies, on the efficacy of probiotics in the prevention and treatment of gastrointestinal disorders, respiratory, and urogenital diseases. Many microbial strains with probiotic properties are able not only to restore the intestinal microbial balance, but also to impart other beneficial effects on health, associated with the production of acids, bacteriocins and with the competition with pathogenic microorganisms. Among these, the main effects are the reduction of the level of cholesterol in the blood, the reduction of fecal enzymes, with potentially mutagenic activity that can induce the onset of tumors, the reduction of lactose intolerance, the increase of the response of the immune system, the increase of calcium absorption, and synthesis of vitamins. ... 

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