Lactic acid bacteria, probiotics and immune system

Mucous membranes of the body are in direct contact with the outside environment and they are colonised by a large number of different bacteria. Through mucous membranes, the organism is in permanent con-tact with different antigens. Mucous surfaces are protected by many defence mechanisms that ensure a permanent and effective protection. They include the production of secretory IgA, the production of mucus, cytoprotective peptides, defensins etc. Indigenous microflora markedly affects the structure of the host mucous, its function, and the development of the whole immune system. Protective microflora prevents pathogens from adhering by competi-tion for substrates and places of adhesion, and they simultaneously produce antibacterial substances and stimulate the production of specific antibodies and mucus. The early colonisation of the gut with living micro-organisms is important for the development of the gut protection barrier. The number of immune and epithelial cells increases. Probiotic micro-organisms including lactic acid bacteria (LAB) positively influence the composition of the gut microflora; they stimulate the production of secretory IgA; they affect the targeted transportation of the luminal antigens to Peyer's patches and they increase the production of IFN-g. LAB stimulate the activity of non-specific and specific immune cells. These properties of the LAB depend on the particular species or strain of bacteria. These singularities are probably determined by differences in the cell wall composition. LAB belong to a group of benefi-cially acting bacteria and they are able to eliminate damage to the gut microenvironment; they stimulate local and systemic immune responses and they maintain the integrity of the gut wall.