Regulates the expression of IL-2, IL-6, and other cytokines through regulation on NF-kappa-B activity. Functions in the regulation of inflammatory responses. Involved in the induction of T helper 17 cells (Th17) differentiation upon recognition of antigen by T cell antigen receptor (TCR). May also regulate TCR-induced negative selection of thymocytes. Interacts with NFKB1, RELA and RELB; in the nucleus. Belongs to the NF-kappa-B inhibitor family.