TNF and infection: The innate immunity acts as the first line of defense against pathogen infection, and macrophages are antigen-presenting cells in the innate immune system that can phagocytose bacteria and produce both proinflammatory cytokines (e.g., tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6), and mediators (e.g., nitric oxide (NO) and cyclooxygenase-2 (COX-2, a key enzyme in the synthesis of prostaglandins)) [7].