Synergistic effects of interferon γ and tumour necrosis factor α on T84 cell function

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Abstract
BACKGROUND Inflammatory bowel disease (IBD) is characterised by chronic intestinal inflammation and increased epithelial permeability. Both tumour necrosis factor α (TNF-α) and interferon γ (IFN-γ) 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-γ and TNF-α 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 (pI 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-γ, TNF-α accelerated IFN-γ dependent changes. Relative to controls, significant changes occurred after one day of culture with IFN-γ plus TNF-α: TER was decreased to 27 (3.5)%, FITC–dextran flux was increased by 185 (45)-fold, and cAMP and Ca dependentI sc were decreased to 66 (12)% and 35 (6.8)%, respectively. TNF-α also enhanced IFN-γ dependent changes in cell morphology but did not induce cell death. CONCLUSION IFN-γ alters T84 cell epithelial properties and TNF-α can enhance these effects, perhaps due to IFN-γ dependent increases in TNF receptor gene expression. Overall, these studies suggest that in IBD, TNF-α may have synergistic effects on IFN-γ mediated alterations of epithelial cell function.

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