A20, also referred to as TNF-alpha-induced protein 3 (TNFAIP3), is cytokine-inducible protein that functions to inhibit apoptosis and activate NF-kB. It was first identified as a TNF-alpha inducible primary response gene in human umbilical vein endothelial cells, and encodes a 790-amino acid protein containing seven Cys2/Cys2-zinc finger motifs. Constitutive expression of A20 is observed in lymphoid tissues, but it is transiently expressed in a variety of cell types in response to inflammatory signals such as TNF-alpha, IL-1, phorbol esters, and LPS. Expression of A20 can confer resistance to apoptosis and NF-kB activation triggered by these signals, probably through interference with TRAF (TNF receptor associated factor) family members, and interaction with the NF-kB inhibiting protein ABIN.