Effects of interferon gamma on growth, apoptosis, and MHC class II expression of immature rat intestinal crypt (IEC-6) cells.

Intestinal epithelial cells and the mucosal immune cells in close proximity are thought to interact very closely. One well-established mechanism of this intercellular cross-talk is via the production of cytokines such as interferon gamma (IFNgamma). The aim of this study was to analyze the effects of IFNgamma on intestinal crypt epithelial cells. IEC-6 cells were cultured in the presence or absence of IFNgamma to measure its effects on proliferation, cell cycle, apoptosis, and major histocompatibility complex (MHC) class II antigen expression. Even at very low doses (0.01 U/ml), IFNgamma significantly inhibited IEC-6 cell proliferation, as demonstrated by reduced 3H-thymidine uptake, stable cell count, and complete arrest in the quiescent G0/G1 phase of the cell cycle. Incubation with supraphysiological doses of IFNgamma (100-1,000 U/ml) did not induce apoptosis, as assessed by morphology and the TUNEL assay. IFNgamma significantly induced de novo IEC-6 class II antigen expression. Tumor necrosis factor alpha (TNF alpha), which alone had no effect, synergistically enhanced this effect of IFNgamma. MHC class II antigen expression was observed to be independent of cell cycle phase. Our results indicate that IFNgamma alters immature crypt epithelial cell turnover and upregulates MHC class II expression. These alterations may be important in the pathogenesis of immune-mediated bowel disorders.