NF- kappaB/p65 (nuclear factor kappa light chain enhancer in B cells p65) is a member of the Rel/dorsal family. This ubiquitously expressed nuclear protein is one subunit of the NF-kappa B complex consisting of a 65 kD transactivating subunit and a 50 kD DNA binding subunit. Both subunits are derived from larger precursor proteins. NF- kappaB acts as a transcriptional activator and was originally identified as an activator of kappa light chain in B cells. NF- kappaB/p65 is bound (with p50) to I kappaB inhibitor in cytoplasm in inactive form. Phosphorylation of I kappaB releases and NF- kappaB which goes to the nucleus to activate gene expression. NF- kappaB can be activated with LPS, TNF- alpha, phorbol ester, or IL-1. The Poly6226 antibody reacts with the C-terminal region of human, mouse, and rat NF- kappaB p50 and has been shown to be useful for Western blotting.