Antimicrobial and immune modulation properties of probiotics

Summary In addition to having nutritional benefits and anti-inflammatory properties, probiotics can also promote an antimicrobial environment in the gut lumen directly by releasing antimicrobial compounds or indirectly through influencing the gut epithelium. Select strains of probiotic bacteria are able to produce and release antibacterial peptides that have selective activity against numerous strains of microbes commonly found in the gut. These peptides directly kill or inhibit the growth of these species in the lumen. Probiotics can also prevent the entry of pathogens into the lamina propria by preventing pathogen adherence and enhancing killing of intracellular pathogens. Probiotics and their components are able to modulate host gene expression, thereby promoting production of defensins, which are active in the lumen against a number of different pathogens, and intracellular heat-shock proteins, which protect the intestinal epithelia from tissue damage. Immune cells, including dendritic cells and T-regulatory cells, are also modulated by probiotics, whereby dendritic cells exposed to some probiotics induce anti-inflammatory responses and generate IL-10-producing T-regulatory cells. In conclusion, probiotics enhance antimicrobial activity in the gut through a number of different mechanisms involving host epithelial and immune cells.