Özet:

The intestinal microbiota is composed of 1013-1014 microorganisms, with at least 100 times as many genes as our genome, the microbiome. Its composition is specific for each individual, changes among individuals and also shows an intra-individual variability during life. Although the gastrointestinal microbial communities of adults are often believed to be stable, there is evidence that, even though at lower rates than in childhood, they change with time, and effects of this variability on health have not been determined yet. The interaction between microbiota and environment is close and widely demonstrated. Gut flora composition is deeply influenced by a number of factors, including diet, age, medications, illness, stress and lifestyle. Intestinal microflora has protective, metabolic and trophic functions. Commensal microbiota can deeply influence the development of the gut mucosal immune system, modulating the maturation of the gut-associated lymphoid tissue and preventing exogenous pathogen intrusion, by stimulation of the immune system and by direct interaction with pathogenic bacteria. The increasing amount of preclinical studies regarding the interaction between intestinal microbiota and immune system and the multiple observations of altered microbiota in human diseases have paved the way for a number of clinical trials aimed at verifying the potential benefits deriving from the manipulation of the microbial ensemble. Several probiotic bacteria have been assessed for their potential applicability in human diseases, albeit with different levels of success. In conclusion, the gut microbiota codevelops with the immune system beginning at birth. The development of the microbiota and its interactions with the cellular populations of the bowel provide a substantial contribution to shaping the structure and dynamic operations of the innate and adaptive immune systems. Manipulation of the microbiota, particularly through the administration of specific probiotic strains, represents a unique opportunity for the development of new therapeutic tools in several human diseases.

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