Synergistic effects of interferon gamma and tumour necrosis factor alpha on T84 cell function.

BACKGROUND: Inflammatory bowel disease (IBD) is characterised by chronic intestinal inflammation and increased epithelial permeability. Both tumour necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) have been implicated in IBD. AIMS: To understand better the effects of these cytokines on epithelial cell function.
METHODS: T84 cells were cultured with IFN-gamma and TNF-alpha and changes in transepithelial resistance (TER), fluorescein isothiocyanate (FITC) dextran flux, short circuit current (I(sc)), cystic fibrosis transmembrane conductance regulator (CFTR) protein levels, cell morphology, TNF receptor gene expression, and apoptosis were assayed.
RESULTS: Relative to controls, significant changes (p<0.05) occurred in cells incubated with IFN-gamma for two days: TER was decreased to 20 (6.2)%, FITC-dextran flux was increased by 109 (19)-fold, cAMP and Ca dependent I(sc) were decreased to 51 (6.4)% and 24 (2.2)%, respectively, and CFTR levels were decreased to 47 (11)%. Cell morphology was altered but cell death was not induced. TNF receptor mRNA levels were increased. When added with IFN-gamma, TNF-alpha accelerated IFN-gamma dependent changes. Relative to controls, significant changes occurred after one day of culture with IFN-gamma plus TNF-alpha: TER was decreased to 27 (3.5)%, FITC-dextran flux was increased by 185 (45)-fold, and cAMP and Ca dependent I(sc) were decreased to 66 (12)% and 35 (6.8)%, respectively. TNF-alpha also enhanced IFN-gamma dependent changes in cell morphology but did not induce cell death.
CONCLUSION: IFN-gamma alters T84 cell epithelial properties and TNF-alpha can enhance these effects, perhaps due to IFN-gamma dependent increases in TNF receptor gene expression. Overall, these studies suggest that in IBD, TNF-alpha may have synergistic effects on IFN-gamma mediated alterations of epithelial cell function.