Probiotics Mechanism of Action on Immune Cells and Beneficial Effects on Human Health

Abstract

Immune cells and commensal microbes in the human intestine constantly communicate with and react to each other in a stable environment in order to maintain healthy immune activities. Immune system-microbiota cross-talk relies on a complex network of pathways that sustain the balance between immune tolerance and immunogenicity. Probiotic bacteria can interact and stimulate intestinal immune cells and commensal microflora to modulate specific immune functions and immune homeostasis. Growing evidence shows that probiotic bacteria present important health-promoting and immunomodulatory properties. Thus, the use of probiotics might represent a promising approach for improving immune system activities. So far, few studies have been reported on the beneficial immune modulatory effect of probiotics. However, many others, which are mainly focused on their metabolic/nutritional properties, have been published. Therefore, the mechanisms behind the interaction between host immune cells and probiotics have only been partially described. The present review aims to collect and summarize the most recent scientific results and the resulting implications of how probiotic bacteria and immune cells interact to improve immune functions. Hence, a description of the currently known immunomodulatory mechanisms of probiotic bacteria in improving the host immune system is provided.

In Vitro Evaluation of the Most Active Probiotic Strains Able to Improve the Intestinal Barrier Functions and to Prevent Inflammatory Diseases of the Gastrointestinal System

“…In recent years, great progress was achieved in the study of the mechanisms of symbiosis between lactic acid bacteria and the host. Their main beneficial effects have been shown to include the regulation of the imbalance of the intestinal flora [ 42 ], the strengthening of the intestinal barrier functions [ 23 , 27 , 36 ], the maintenance of homeostasis [ 36 , 43 ], the regulation of the immune system [ 43 ], and the production of neurotransmitters (gut–brain axis) [ 44 ]. It has been also shown that the exopolysaccharide (EPS) produced by lactobacilli has the peculiar ability to modify the microbiota [ 45 ], and to improve the colonization and growth of intestinal bacteria by acting as a carbon source [ 46 ].…”

“…It was demonstrated that the intake of probiotic bacteria contributes to a proper intestinal functioning by maintaining the epithelial permeability, enhancing the mucous layer, increasing enterocyte turnover, stimulating the innate and adaptative immune response and restoring gut microbiota composition and activity [ 23 , 24 ].…”

The Role of Probiotics and Their Metabolites in the Treatment of Depression

“…Furthermore, norepinephrine has been identified as a factor that increases proliferation of pathogens such as Escherichia coli , Yersinia enterocolitica , and Pseudomonas aeruginosa [ 145 ]. Deficiencies in catecholamine concentration might contribute to neurodegenerative diseases such as Alzheimer’s and Parkinson’s disorders and MDD [ 148 ]. The effect of probiotics on catecholamine metabolism was determined in animal models.…”

Probiotic-derived ecto-5'-nucleotidase produces anti-inflammatory adenosine metabolites in Treg-deficient scurfy mice

“…Probiotics have the capacity to induce large-scale changes in the host microbiota composition and also to modulate the global metabolic function of the intestinal microbiome [20][21][22]. Probiotic DSM 17938 has been shown to have a mutualistic relationship between microbe and host [23][24][25].…”