抄録
The lumen of the gut is separated form the internal milieu by an intestinal barrier comprising epithelial cells connected by tight junctions. The barrier inhibits passage of HRP (horse raddish peroxidase) and other tracer molecules. This lecture deals with following problems concerning the intestinal barrier and substance transfer through it. 1. For a short period after birth, substances are pinocytosed by the epithelial cells of the small intes-tine and conveyed to the internal milieu. 2. Coarse substances, even bacteria and viruses, may be taken up and transferred by M cells on Peyer's patches. 3. The intestinal barrier has been suspected to be broken at the tip of intestinal villi where effete epith-elial cells are exfoliated. We recently demonstrated in the guinea pig that the apoptotic epithelial cells are, only in their basal, principal portion, lysed and phagocytosed by large granular lymphocytes (LGLs) and macrophages, while their apical portion remains at the site. During the process of this cell apex being pinched off by pressure of surrounding cells, the tight junctions are preserved by the latter cells (Iwanaga et al. 1992, Han et al. 1993). Thus, in the guinea pig, likely also in the monkey and in humans, the intesti-nal barrier is not broken due to epithelial cell death.
