PTGS2 and infection: COX-1 is constitutively expressed in a wide range of tissues to maintain homeostatic prostanoids that are essential for many biological functions such as angiogenesis, vasodilatation, platelet function, tissue maintenance, etc. COX-2 is usually present at low levels under normal conditions, but is rapidly and robustly induced by stimuli including infection, injury and pain to initiate pro-inflammatory processes that could facilitate and maintain the disease states3–5.