NF-κB (Nuclear Factor κ B) is a nuclear transcription factor found in all cell types and is involved in cellular responses to stimuli such as stress, cytokines, free radicals, ultraviolet irradiation, and bacterial or viral antigens. NF-κB plays a key role in regulating the immune response to infection. Consistent with this role, incorrect regulation of NF-κB has been linked to cancer, inflammatory and autoimmune diseases, septic shock, viral infection and improper immune development. There are five members in the NF-κB family: NF-κB1, NF-κB2, RelA (also named p65), RelB, and c-Rel. RelA(p65) subunit of NF-κB is a crucial regulator of apoptosis. RelA subunit mediates resistance to programmed cell death induced by many stimuli, including TNF, chemotherapy agents and ionizing radiation, through inducing the expression of a wide variety of anti-apoptotic genes. NF-κ-B is a pleiotropic transcription factor which is present in almost all cell types and is involved in many biological processed such as inflammation, immunity, differentiation, cell growth, tumorigenesis and apoptosis. NF-κ-B is a homo- or heterodimeric complex formed by the Rel-like domain-containing proteins RELA/p65, RELB, NFKB1/p105, NFKB1/p50, REL and NFKB2/p52 and the heterodimeric p65-p50 complex appears to be most abundant one. The dimers bind at κ-B sites in the DNA of their target genes and the individual dimers have distinct preferences for different κ-B sites that they can bind with distinguishable affinity and specificity. Different dimer combinations act as transcriptional activators or repressors, respectively. NF-κ-B is controlled by various mechanisms of post-translational modification and subcellular compartmentalization as well as by interactions with other cofactors or corepressors. NF-κ-B complexes are held in the cytoplasm in an inactive state complexed with members of the NF-κ-B inhibitor (I-κ-B) family. In a conventional activation pathway, I-κ-B is phosphorylated by I-κ-B kinases (IKKs) in response to different activators, subsequently degraded thus liberating the active NF-κ-B complex which translocates to the nucleus. NF-κ-B heterodimeric p65-p50 and p65-c-Rel complexes are transcriptional activators. The NF-κ-B p65-p65 complex appears to be involved in invasin-mediated activation of IL-8 expression. The inhibitory effect of I-κ-B upon NF-κ-B the cytoplasm is exerted primarily through the interaction with p65. p65 shows a weak DNA-binding site which could contribute directly to DNA binding in the NF-κ-B complex.