Review : The Role of the Immune System in the use of Probiotic Lactic Acid Bacteria in Preventing and Treating Allergic Diseases

The immune system is generally divided into the innate and the adopted immune systems, both protecting the body from pathogens. Recently, allergies, a disease associated with an imbalanced immune system, have increased rapidly in developed countries. Prevailing symptoms of allergic diseases are eczema, allergic rhinitis, asthma, inflammatory bowel disease, and food allergy. Probiotic bacteria, mainly consisting of lactic acid bacteria, are used in the prevention and treatment of allergic diseases. The function of them is to stimulate the intestinal immune cells and form a complex signal network to activate other immune cells. Beneficial health effects of probiotics are based on the hygiene hypothesis, which suggests that sanitary environment is important for health, but limited exposure to environmental factors increases allergic diseases. An immunoregulatory effect of probiotic bacteria is demonstrated by controlled trial, animal model, in vitro, in vivo and ex vivodesigns. However, the immunoregulatory effect of probiotic bacteria is controversial because it depends on probiotic strains, a dose and a type of diseases. In this review, we discussed clinical evidences on immunoregulatory effects of probiotic bacteria.