TNF and infection: The present study investigated whether SaaS mediated the secretion of cytokines in vivo, with the interleukin (IL)-1β, IL-6, IL-18, tumor necrosis factor-α (TNF-α), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) levels in colon after infection examined with ELISA or RT-qPCR (Figure 1c).