TNF and infection: Infection, injury and irritants such as lipopolysaccharide (LPS) lead to the activation of microglia and the release of various cytokine and chemokine factors including cyclooxygenase-2 (COX-2) and inducible nitric oxide (NO) synthase (iNOS), inflammatory modulators such as prostaglandin E2 (PGE2) and NO, proinflammatory cytokines such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) [1,2,3,4].