Fetal characteristics of small intestinal crypt cells.

Nine monoclonal antibodies were prepared against luminal membranes purified from rat intestinal cells at day 19 of gestation, and seven of them were found to define antigens common to adult crypt cells and fetal or embryonic intestinal epithelial cells. The FBB 2/29 antigen was first detected over the entire intestinal epithelial population at days 14-15 of gestation, a period of development characterized by formation of a stratified intestinal epithelium and differentiation of the surrounding mesenchyme. This antigen, identified as a set of high molecular mass proteins, became restricted to the crypt and lower villus cells after birth and was exclusively expressed by the crypt cells in adult intestine. It also was found to be expressed by the epithelial cells of the distal tubuli in the kidney of adult rats and by cultured human tumor colonic cells. The FBB 1/54/1, FBB 3/46, and FBB 3/78/9 antibodies stained only the epithelial cells present at the base of the villi in fetal intestine, starting at days 20-21 of gestation (about 1-2 days before birth), and stained the crypt and lower villus cells in newborn and adult intestine; these antigens may be regarded as specific markers for the developing crypt cells in fetal intestine shortly before birth. The FBB 1/20 and FBB 4/2 antigens were first detected on the fetal intestinal cells at day 18 of gestation; they were located over the entire epithelium in newborn rats and became restricted to the crypts after weaning. The FBB 2/28 antigen was expressed by the entire intestinal epithelium at all stages of development, starting from days 18-19 of gestation in the fetus. Two antibodies, FBB 3/4 and FBB 3/24, were found to be specific for lactase. These results have demonstrated the expression of cell- and tissue-specific components in rat intestine during early embryonic development and revealed a marked similarity in surface membrane antigens between fetal intestinal epithelial cells and adult crypt cells.