Acts as a negative regulator of innate and adaptive immunity by maintaining immune homeostasis. Negative regulator of Toll-like receptor and T-cell receptor function. Prevents hyperresponsiveness of the immune system and maintains immune homeostasis. Inhibits jun/ap1 and NF-kappa-B activation. Promotes Fas-induced apoptosis (By similarity). The central region was initially thought to constitute a DED (death effector) domain. However, 3D-structure data reveal a previously uncharacterized fold that is different from the predicted fold of a DED (death effector) domain. It consists of a large, hydrophobic central cavity that is poised for cofactor binding (By similarity). Belongs to the TNFAIP8 family. TNFAIP8L2 subfamily.