Intestinal microbiota as a key factor in the formation of immunity and tolerance. Probiotics capabilities

Abstract

Introduction. The intestinal microbiome is an integral part of the health of its owner and performs several important functions: metabolic, coordinating, protective, epigenetic, which are closely interactive. In conditions of dysbiosis, disturbances of these functions contributes to different disorders.The intestinal immune system closely interacts with the microbiota. It is represented by all cells: T- and B-lymphocytes, T-regulatory, dendritic cells, macrophages. Micropresentation of antigens occurs through M-cells located between enterocytes. Toll-like receptors that recognize bacterial patterns are presented on the epithelial membrane. Dendritic cells present these antigens to T-cells and direct a further adaptive immune response.The immune system matures as a result of colonization of the intestine with microbiota, which is confirmed experimentally in gnotobiotic animals. Under physiological conditions, the immune system provides tolerance to its own microbiota through Tr-cells. Tolerogenic effects decrease in dysbiotic conditions, as a result, inflammation develops.The state of the intestinal barrier. The intestinal barrier is maintained by microbiota, which stimulates the synthesis of mucin and claudine. In dysbiosis, permeability increases, and the immune system is attacked by microbes and their metabolites, which contributes to inflammation.Dysbiosis predisposes to the development of inflammatory bowel diseases, colorectal cancer, metabolic syndrome and obesity, food allergies. In these diseases, the microbiota loses its diversity and richness and has a predominantly pro-inflammatory effect.The effect of probiotics on the immune system. Probiotics, due to adhesion to the mucous layer, enhance barrier functions, interact with the immune system, affect dendritic cells, promoting the formation of Tr and inhibiting the activation of NF-kB. Commensal metabolites (butyrate) increase the involvement of Tr cells in the colon, exerting a tolerogenic effect.Indications for the appointment of probiotics. Enterococcus faecium and Bifidobacterium longum have proven their activities similar to normal microbiota, and effectiveness in treatment of dysbiosis in children and adults.