Mucosal immunity, intestinal microflora and inflammatory bowel disease

摘要

Immediately after biith the epithelial surfaces come into contact with numbers of microorganisms. These surfaces have evolved a number of protective mechanisms to resist the invasion of microorganisms. While the skin surface (about 2 m2) is protected mechanically by several epithelial layers, surfaces of the gastrointestinal, respiratory and urogenital tracts, conjunctivae and outlets of endocrine glands (about 300 m2) are mostly covered with a single-layered epithelium and therefore require more extensive protection: this is represented by a complex of mechanical and chemical agents responsible for effective degradation and removal of heterogeneous substances (Table 1). In addition, both the mucosa and the internal environment of the organism are protected by most effective innate and highly specific immune systems. The basic functions of the mucosal immune system are protection against pathogenic microorganisms and prevention of penetration of immunogenic components from mucosal surfaces into the internal environment of the organism (barrier and anti-infectious functions). Another important function is induction of unresponsiveness of the systemic immunity to antigens present on mucosal surfaces ('oral, mucosal tolerance') and maintenance of homeostasis on mucosal surfaces (immunoregulatory function).