[The interrelations of mucosal epithelial cells with microbes--intracellular parasites]

On the basis of information at hand, it can be concluded that there are principal limits on the capture of bacteria by epithelial cells in the gastrointestinal tract and other cavities. Although entry is, however, a result both of bacteria and epithelial cells, it is frequently induced by parasite-directed endocytosis and may also accompanied by passive entry of nonpathogenic bacteria. The induction of parasite-induced endocytosis should be regarded as a consequence of a fundamental concept in biology, namely: molecular and cellular recognition wherein bacterial adhesion to the host's cell receptors is of great importance. In this connection, discussion covers the origin of corresponding receptors. The authors share the opinion in that epithelial cells, those of the gastrointestinal tract in particular, are part of the human common mucosal immune system.