| Abstract: | It is known that two major cytotoxins, lymphotoxin (LT) and tumour necrosis factor (TNF), are produced by T cells and macrophages, respectively. We report in this paper that a human T-cell hybridoma, AC5-8, produces TNF in addition to LT depending on the kind of stimuli used. When phorbol myristate acetate (PMA) and concanavalin A (Con A) or PMA alone were used to induce AC5-8 cells to secrete a cytotoxin, we found that the cytotoxin secreted was antigenically indistinguishable from LT. On the other hand, when AC5-8 cells were activated by PMA and A23187, they secreted another cytotoxin which was antigenically indistinguishable from TNF, in addition to LT. These two cytotoxins could be separated by affinity chromatography on a column of Con A-Sepharose. A cytotoxin, which did not bind to the Con A-Sepharose column and showed about 70-95% of the total cytotoxic activity secreted from AC5-8 cells stimulated with PMA and A23187, was found to be antigenically identical to TNF. The other cytotoxin, which bound to the Con A-Sepharose column and showed only 5-30% of the total activity induced by PMA and A23187, was found to be antigenically identical to LT. |
