CXCL8 and irritable bowel syndrome: However, measurement of cytokine levels in biopsy supernatants failed to show any difference in IL-4, IL-13, IFN-γ, IL-1β, CXCL8, IL-10, IL-17a, TNF-α, MCP-1 and IL-6 levels between HVs and PI-IBS (Fig. 5), and no significant difference was seen in biopsy transcript levels for a panel of pro- and anti-inflammatory cytokines (IFN-γ, TNF-α, IL-6, IL-1β, MCP-1, IL-4, IL-10, IL-17f, IL-5, IL-13 and IL-2) for PI-IBS and HVs (Fig. 6A).