Funktionelle Morphologie der Schleimhaut-Schranke
Journal/Book: Mikro÷kologie und Therapie. 1984; 14: 137-168.
Abstract: Among the -outer and inner surfaces of the human body, the 200 to 300 m2 of the gut contrast with the approximately 2 m2 of the skin, and the 80 m2 of the lung. At the inner surface of the intestine intimate contact takes place between the mammalian organism and bacteria, parasites, toxins, a wide variety of dietary substances and their breakdown products. It is estimated that the normal human person carries 1014 bacteria in the intestinal tract, 1010 in the mouth and 1012 an the skin. In most individuals, at most times, this bacterial population includes organisms which are conventionally classified as pathogens.The essential barrier against the permanent antigenic burden is the mucosa, i. e. mainly its lamina epithelialis. It prevents penetration of potentially noxious agents, but allows exchange of substances between the gut lumen and the "milieu interieur" of the body. This barrier is a complex organ composed of different types of epithelial cells, which have different physiological functions and capabilities and which are continuously desquamated into the lumen. The integrity of this organ depends upon the continual replication, maturation, and metabolism of its constituent cells. Additional defense functions are exerted by the mucus, lysozyme of Paneth cells and phagocytes, granulocytes, macrophages, immunologic mechanisms and other factors. It is hardly surprising that the intestine is equipped with an extensive immune apparatus. This local immune system functions fairly independently of the systemic immunity. Some of the factors involved in mucosal immunity are being produced very close to the surface at which they act. The sum of the mechanical, humoral, cellular, immunologic and non-immunologic defense factors of the intestinal mucosa constitutes the mucosal block.