TNF and endometritis: Uterine infections induce the production and release of proinflammatory cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β, which, in turn, activate phospholipid metabolism, arachidonic acid release and the signal transduction system involving nuclear factor (NF)-κB to increase the expression of cyclooxygenase (COX)-2, which provokes the production of prostaglandin (PG)-E2 and PG-F2α, both of which stimulate contractility by activating the phospholipase-C/Ca2+ (PLC) pathway.