TNF and infection: Compared to mock infected mice, transcript levels of the pro-inflammatory genes Nos2, encoding inducible nitric oxide synthase (iNOS), and Tnfa, encoding tumor necrosis factor (TNF)-α, were significantly (P<0.05) elevated in the cecal mucosa at 12 hours after infection with a non-flagellated S. Typhimurium phoN fliC fljB mutant (SW793) (Fig. 6B and C).