We have assembled a system for testing the hypothesis that changes in glycoconjugate production represent markers for defining developmental, spatial, and environmental influences on the proliferation and differentiation programs of various mouse gut epithelial cell lineages. Multilabel immunohistochemical methods were used to survey the interactions of purified lectins with 1) normal fetal, neonatal, and adult FVB/N mouse gut, 2) gastric and intestinal isografts harvested at various developmental stages, and 3) transgenic mouse models of intestinal epithelial cell hyperplasia, dysplasia, and/or neoplasia. As a demonstration of the system's utility, we used the recently purified, α-N-acetyl-D-galactosamine-specific, Moluccella laevis lectin (MLL). In the adult FVB/N mouse stomach, MLL only recognizes glycoconjugates produced by a population of nonproliferating neck and prezymogenic cells that occupy a pivotal point in the complex, migration- associated differentiation program of the zymogenic cell lineage. In the developing FVB/N stomach, MLL binds to members of the zymogenic and pit lineages even before morphogenesis of gastric units is completed. Expression of MLL epitopes in pit cells is restricted to the period before the gastric epithelium has completed its morphoregulatory program. Analysis of gastric isografts indicates that these lineage-and developmental stage-specific patterns of glycoconjugate accumulation are not influenced by normal luminal contents. In the adult FVB/N intestine, MLL binding can be used to operationally define variations in the differentiation programs of 1) members of the enteroendocrine and goblet cell lineages daring their migration along the crypt-to-villus axis and 2) cells comprising the follicle-associated epithelium overlying Peyer's patches. Accumulation of MLL epitopes in villus- associated enterocytes does not appear to be affected when these cells are induced to reenter the cell cycle by simian virus 40 large T antigen (SV40 TAg). MLL reactivity is not diminished when enterocytes begin to dedifferentiate as a result of production of SV40 TAg, human K-ras(Val12), and a dominant negative human p53 mutant. The lack of change in MLL binding properties may reflect the brief residence time of enterocytes on the villus. These results indicate that glycoconjugate production represents a very useful tool for studying gut epithelial cell biology. Preliminary studies suggest that this is also true in the human gut.