Nuclear factor (NF)-kappa B is a sequence specific transcriptional activator that binds to the intronic enhancer of kappa light chain gene in B lymphocytes. NF-kB regulates the expression of a wide variety of genes that involved in apoptosis, viral life cycle, tumorigenesis, autoimmune diseases and inflammation. NF-kB is a heterodimer of members of the rel family of proteins such as p50, p65, and c-rel. In most cells, inhibitory IkB proteins sequester NF-kB/Rel in the cytoplasm. Cellular stimulation precipitates degradation of IkB and modification of NF-kB/Rel proteins, permitting translocation of NF-kB/Rel (c-Rel and RelA) to the nucleus for action on target genes. The important role of c-Rel in B-cell development, growth, and survival has been intensively studied, as well as its function in differentiation and lymphopoiesis (particularly lymphoid cancer).