Likewise, the level of IL-6 gradually increased during the course of infection in the WT S. typhimurium-infected group of mice and reached the highest level on day 14 p.i. However, the levels of IL-6 in either of the mutant-infected mice increased somewhat on day 3 p.i. and declined on day 7 p.i., followed by its increase on days 14 or 21 p.i. (Figure 2B). Here, IL6 is linked to infection.