The most extensive interaction between the human organism and its external and internal environment occurs at the mucosal membranes of the digestive, respiratory and urogenital tracts. Mucosa-associated lymphoid tissue -MALT represents an effector and an inductive site of the immune system and it enables the transfer of information about different antigens between different mucosal membranes, enhancing the immune integrity of the entire human organism. The intestinal mucosa is especially exposed to a lifelong strong antigenic stimulation, therefore a unique immune response takes place on it, characterized primarily by limited ,,physiological“ inflammation, immune tolerance, elimination of harmful and persistence of beneficial antigens. Homeostasis is maintained by a complex interplay between various anti-inflammatory and pro-inflammatory patterns that can produce homeostatic outcomes, such as the creation of oral tolerance and elimination of harmful noxes. The prevalence of proinflammatory stimuli and pathways leads to chronic persistent inflammation and tissue destruction. Impaired homeostasis along with leaky intestinal barrier represents a central event in many intestinal and extraintestinal diseases.

Key words:
endoplasmic reticulum stress; host-microbial interactions; immune tolerance; intestinal mucosa; mucosal immunity