TNF and infection: Whereas proinflammatory cytokines (e.g., IL-1, IL-6, and tumor necrosis factor α-[TNF-α]) appear within one hour after the start of bacterial infection, and procalcitonin (PCT) after 5 hours, the hepatic synthesis of CRP starts 6 to 8 hours after onset [12] and peak concentrations are reached between 36 to 50 hours after infection has started.