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 (PubMed:11931770, PubMed:15749903, PubMed:16410444, PubMed:16413922, PubMed:17641034). Involved in the induction of T helper 17 cells (Th17) differentiation upon recognition of antigen by T cell antigen receptor (TCR) (PubMed:25282160). According to PubMed:11931770, it may also regulate TCR-induced negative selection of thymocytes (PubMed:11931770). Interacts with NFKB1, RELA and RELB; in the nucleus. Specifically expressed in spleen and at low levels in thymus. Expressed in a population of antigen-presenting dendritic cells which may act as regulators of systemic inflammatory response. Up-regulated in thymocytes upon TCR-triggered cell death (at protein level). Up-regulated by IL-10 or LPS. Mice are highly sensitive to LPS-induced endotoxin shock and susceptible to intestinal inflammation caused by exposure to microflora. They display no overt T-cell selection phenotype but an impaired proliferation of T-cells. Thymocytes and T-cells seem to produce less IL-2 and IFNG. Belongs to the NF-kappa-B inhibitor family.