NOS2 and infection: The effector functions of the M1 macrophages are characterized by the production of proinflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6, and the expression of inducible nitric oxide synthase (iNOS), which recruits other types of immune cells to the infection or injury site [25,26,27,28,29,30].