Tumour necrosis factor (TNF) is an inflammatory cytokine possessing a unique property: it can induce cells to undergo apoptosis. The sensitivity of different cell types to TNF-induced apoptosis can vary dramatically, but most cells become very sensitive upon simultaneous treatment with inhibitors of protein synthesis. It has been suggested therefore that a gene, or set of genes, is induced upon TNF receptor activation that downregulates the apoptosis signal. Recent results have shown that NF-kappa B, a transcription factor activated upon TNF signalling, is at least partly responsible for this effect. These findings have broadened the role of NF-kappa B from that of a regulator of immune and inflammatory responses to include an involvement in the regulation of apoptosis.