The plasma TNF-α peaked 1 h after the start of the E. coli infusion while the IL-6 levels peaked 3 h after in both groups; the peak levels were higher in the naive group (p < 0.001) than in the SIRS group (p < 0.001) and the control group (p < 0.001; Fig. 4). Here, TNF is linked to systemic inflammatory response syndrome.