TNF and infection: In the normal human body, the levels of cytokines and chemokines are always low; it is only when the body repairs the physical damage caused by injury or infection that the levels of cytokines in the body, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and nitric oxide (NO), increase, ultimately leading to the development of inflammation (Dell'Agli et al., 2013).