Identity of human B-cell line cytotoxic lymphokine with tumor necrosis factor type beta.

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Abstract
A humoral cytotoxic protein that is spontaneously produced by a cloned human lymphoblastoid cell line (K160b) was partially purified by a simple three-step column chromatography procedure and NaDodSO4/polyacrylamide gel electrophoresis. Proteins were electrically blotted onto a polyvinylidene difluoride membrane, and a band of the cytotoxic protein was excised after staining with Coomassie brilliant blue. Direct analysis of the amino acid sequence of this protein showed the primary structure of its N-terminal region was identical to that of natural tumor necrosis factor type .beta. (TNF-.beta.). The 24-kDa molecular mass of the cytotoxic protein, determined by NaDodSO4/PAGE, and its elution profiles from various types of columns correlated with those of natural TNF-.beta.. Specific activity of the cytotoxicity, standardized with recombinant TNF-.beta., was comparable to that of the purified factor. However, polyclonal antiserum to recombinant TNF-.beta. failed to react with the purified factor. Since recombinant TNF-.beta., when used in patients, causes unacceptable side effects, which may be due to absence of glycosylation, the cell line K160b could be a useful source of natural TNF-.beta. for clinical trials.