TNF and infection: However, when noninfected macrophages were previously treated with PPARβ/δ agonist (white bars), proinflammatory IL-6 was upregulated, and its expression was held during infection; TNF-α and IL-1β were overexpressed, but they were downregulated at 30 to 60 min (after infection), and its expression recovered at 120 min (after infection).