LEFTY2 and infection: Alternatively, as the pro-inflammatory IL-6 mRNA expression was decreasing, the S. Enteritidis infection persisted, and the expression of the anti-inflammatory cytokine TGF-β4 mRNA were significantly up-regulated over the course of the 14-day infection period with the most profound up-regulation of both between 7 and 10 days post-infection when compared to the non-infected controls birds (Figure 1).