NK cells recognize the target cells and are activated through germ-line encoded immune receptor.[14] Representatively, the natural killer group 2 member D (NKG2D) receptor in NK cells detects UL16 binding proteins (ULBPs) and MICA/B, which are increased when DNA is damaged, or in cases of cancer and viral infection.[15] NK cells also recognize the deficiency of MHC Class I and remove the missing self.[16] In addition, NK cells interact with dendritic cells, macrophages, and T cells and regulates inflammatory reactions through the production of cytokines such as IFN-γ or TNF-α. Here, TNF is linked to viral infectious disease.