TNF and infection: NK cells can produce various cytokines and chemokines, i.e., IFN-γ, TNF-α, granulocyte-macrophage colony stimulating factor (GM-CSF), macrophage inflammation protein (MIP)-1β and RANTES (Regulated on Activation, Normal T cell Expressed and Secreted) in response to infection and play an important role in the control of viral, parasitic and certain intracellular bacterial diseases [99,100].