<unk>  refers to a set of recently discovered cellular based anti-viral defense mechanisms, notably genetically encoded proteins which specifically target eukaryotic retroviruses. Unlike adaptive and innate immunity effectors,<unk>  immune proteins are always expressed at a constant level, allowing a viral infection to be halted quickly.
Intrinsic immunity
Immunity 
Cellular memory
Innate immune system
Adaptive immune system
Autoimmunity
Drug metabolism
Graft versus host