Interleukin-4 and IFN-γ differentially stimulate macrophage chemoattractant protein-1 (MCP-1) and eotaxin production by intestinal epithelial cells

When the intestine becomes infected by pathogenic organisms, intestinal epithelial cells (IEC) respond with the production of chemokines, which then attract and activate specific subsets of leukocytes. During chronic inflammation, the panel of IEC chemokines produced likely represents the net effect of a plethora of mediators present in the milieu, including cytokines from activated T lymphocytes. To explore the influence of T lymphocyte cytokines, we treated IEC-18 cells with interferon-γ (IFN-γ) and interleukin-4 (IL-4) and measured the effect on production of the CC chemokines, monocyte chemoattractant protein-1 (MCP-1) and eotaxin, and the CXC chemokine, macrophage inflammatory protein-2 (MIP-2). Both IFN-γ and IL- 4 enhanced MCP-1 mRNA levels but with different kinetics. IFN-γ stimulated a transient increase in MCP-1 mRNA levels, which peaked at 2 h, whereas IL-4- stimulated MCP-1 mRNA levels were markedly increased at 1 h and remained elevated at all time points studied. With each stimulus, the increase in MCP- 1 mRNA levels was accompanied by a steady time-dependent increase in MCP-1 secretion. In addition, treatment with IFN-γ or IL-4 enhanced IL-1β- stimulated MCP-1 mRNA production and protein secretion. Eotaxin mRNA was detectable in unstimulated IEC-18 cells, and IL-4 but not IFN-γ caused a rapid enhancement in levels, which remained elevated for 24 h after treatment. Finally, IL-1β but not IFN-γ or IL-4 enhanced MIP-2 mRNA levels. Knowledge gained from studying the outcome of T lymphocyte-derived stimuli will help understand the complex sequence of events during chronic intestinal inflammation.