INTERFERON-GAMMA INDUCES A CELL-SURFACE PHENOTYPE SWITCH ON T84 INTESTINAL EPITHELIAL-CELLS

Intestinal epithelia are in intimate contact with submucosal and intraepithelial lymphocytes. The concentration of intraepithelial lymphocytes increases during inflammatory processes, and, when stimulated, these cells generate cytokines such as interferon-gamma (IFN-gamma). In this study, we examined the effect of recombinant human IFN-gamma on ion transport events in T84 cells, a crypt epithelial cell line widely used to study electrogenic Cl- secretion, the transport event responsible for mucosal hydration. Epithelial exposure to IFN-gamma brought about a marked attenuation in stimulated Cl- secretion, as measured by generation of short-circuit current (I-sc) This IFN-gamma-elicited decrease in the Cl- secretory response was present for a variety of specific agonists, appeared largely due to IFN-gamma interactions with the basolateral surface, and did not result from a defect in second messenger generation. Efflux and uptake studies were utilized to functionally define the individual cell surface transport proteins that participate in Cl- secretion and revealed that, in response to epithelial exposure to IFN-gamma, apical Cl- channels and basolateral Na+-K+-2Cl(-) cotransporters, K+ channels, and Na-K-adenosinetriphosphatase were all functionally downregulated. [H-3]bumetanide binding assays suggested that surface expression of the cotransporter was diminished by >70% after IFN-gamma preexposure. Concurrently, surface immunofluorescence studies revealed that epithelial exposure to IFN-gamma brought about the induction of major histocompatibility complex (MHC) class II molecule expression on T84 epithelial monolayers and markedly increased MHC class I surface expression. Finally, neutrophilepithelial adhesion studies revealed that preexposure of epithelial monolayers to IFN-gamma elicited a beta(2)-integrin-dependent induction of neutrophil adhesion. These results suggest a global ''phenotypic switch'' on the intestinal epithelial cell surface from one exhibiting classical epithelial transport function to one expressing significant immune accessory function.