IFNG and irritable bowel syndrome: IBS is sometimes described as a mild chronic inflammation caused by elevated pro-inflammatory cytokine levels, and many studies have reported that IBS patients have significantly higher serum levels of pro-inflammatory cytokines (e.g. TNF-α, IL-1β, IL-6, IL-12, and IFN-γ) and chemokines (e.g. IL-8 and MCP-1) than healthy controls (31–33).