The proposed studies are designed to test the hypothesis that Necrotizing Enterocolitis (NEC) is a disease of immature intestinal host defense triggered by the introduction of artificial feedings and propagated by an inappropriate microbial colonization and enterocyte response. To test this hypothesis, the P.I. will study human fetal in vitro intestinal models by further characterizing an established human intestinal non-malignant epithelial cell line as to the function (including receptor expression, signal transduction and effector response), microenvironmental factors affecting differentiation and using SV-40 large T antigen construct to immortalize these cells. The P.I. will also study initial bacterial colonization of the human gut and define immaturities of bacterial- enterotoxin "crosstalk" including adherence, colonization and translocation of pathologic bacteria, mechanisms of glycosyltransferase activity leading to colonization, endotoxin-immature enterocyte interaction as well as the ontogeny of Paneth cell cryptdin expression. The final aim is designed to use human in vitro intestinal models to study mechanisms for strategies to prevent pathologic bacterial colonization.