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

Background-Inflammatory bowel disease (IBD) is characterised by chronic int estinal inflammation and increased epithelial permeability. Both tumour nec rosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) have been i mplicated 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) dextra n flux, short circuit current (I-sc), cystic fibrosis transmembrane conduct ance regulator (CFTR) protein levels, cell morphology, TNF receptor gene ex pression, and apoptosis were assayed. Results-Relative to controls, significant changes (p<0.05) occurred in cell s incubated with IFN-gamma for two days: TER was decreased to 20 (6.2)%, FI TC-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 we re decreased to 47 (11)%. Cell morphology was altered but cell death was no t induced. TNF receptor mRNA levels were increased. When added with IFN-gam ma 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 b y 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 ch anges in cell morphology but did not induce cell death. Conclusion-IFN-gamma alters T84 cell epithelial properties and TNF-alpha ca n enhance these effects, perhaps due to IFN-gamma dependent increases in TN F receptor gene expression. Overall, these studies suggest that in IBD, TNF -alpha may have synergistic effects on IFN-gamma mediated alterations of ep ithelial cell function.