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NUCLEAR factor κB" (NF-κB"), which was first detected by its binding to the κB" site in the immunoglobulin κ-gene enhancer¹, is important for the regulated expression of the κ-gene^2,3 and is partly responsible for the induction in appropriate cells of inter-leukin-2 (IL-2) ⁴, IL-2α receptor⁵, β-interferon^6,7 and serum amyloid A protein⁸. NF-κ" is present as a nuclear DNA-binding protein in B lymphocytes and mature macrophages, but is found in the cytoplasm of many cells in a form unable to bind to DNA⁹. The cytoplasmic form is bound to an inhibitor protein, IκB, from which it can be released in vitro by deoxycholate and other agents¹⁰. Activation of cells by various agents, notably the phorbol esters that stimulate protein kinase C (PKC), leads to dissociation in vivo of the NF-κB/IκB complex and migration of NF-κB to the nucleus⁹. Therefore, it acts as a second messenger system, transducing activation signals from the …