p65 is a subunit of the nuclear factor kappa B. The transcription factor NFkB is widely recognized as a critical mediator of immune and inflammatory responses. In most cell types, NFkB is found in the cytoplasm where it is associated with an inhibitory protein known as IkB. An impressive variety of stimuli (tumor necrosis factor, interleukin 1, T cell activation signals, bacterial endotoxins, viral transforming proteins, certain growth factors and reactive oxygen intermediates) lead to the rapid nuclear accumulation of NFkB by the induced phosphorylation and subsequent degradation of IkB. In the nucleus, NFkB regulates genes encoding cytokines, cytokine receptors, cell adhesion molecules, proteins involved in coagulation and genes involved in cell growth control. Additionally, NFkB is thought to be an important transcriptional regulator for HIV. Growing evidence indicates that the dysregulation of NFkB may be key to a number of diseases including arthritis and other inflammatory diseases, Alzheimer's disease, atherosclerosis and cancer.