PTGS2 and infection: Activated macrophage plays key roles in host defenses against infection with pathogens, to initiate phagocytic activities and promote inflammatory responses via producing various inflammatory factors, e.g., nitric oxide (NO) and prostaglandin E2 (PGE2); pro-inflammatory mediators, e.g., nitrogen species, inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), metalloproteinases; and pro-inflammatory cytokines, e.g., tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β), and IL-6, that recruit additional immune cells to the sites of infection or tissue injury [2,3,4].