CXCL8 and infection: Both F4+ETEC and ETEC-derived flagellin are known to trigger the fast secretion of pro-inflammatory cytokines by porcine IECs at the early stage of infection, such as TNF-α, prostaglandin E2 (PGE2), IL-6, IL-8 and IL-1α [16, 31, 33, 34], which are intended to disarm or destroy invading bacteria.