Facts and problems of the intestinal basement membrane.

The importance of the intestinal subepithelial basement membrane has been the topic of a new field of gastrointestinal research. Its chemical structure consisting of collagenous and noncollagenous multidomain macromolecules has become unraveled with the help of specific antibodies. Functional aspects have been tested in cell cultures and tissue recombination experiments. Here, current data are reviewed and remaining problems specified. The persistent influence of the subepithelial myofibroblast on the formation and maintenance of the subepithelial basement membrane and the reciprocal interaction between epithelial cells, their basement membrane and the myofibroblast suggest a broader definition of the intestinal epithelium to include these elements.