TNF-ALPHA-INDUCED APOPTOSIS IN DAUDI CELLS - MULTIPARAMETRIC ANALYSIS

Tumour necrois factor alpha (TNF-alpha) is a cytokine that induces phy siological and pathophysiological effects in the immune system, In thi s study we analyzed its action on a human lymphoma cell line (Daudi ce lls) after 1 h, 6 h and 24 h of incubation, Using vital DNA stains, DN A gel electrophoresis, in situ nick translation, transmission electron microscopy and flow cytometry we showed that as early as after 6 h of treatment, target cells were able to undergo death by apoptosis, This was associated with cell shrinkage, chromatin condensation, apoptotic bodies in the cytoplasm without the typical DNA fragmentation into lo w molecular weight nucleosomes, Of interest was the observation of a s ignificant number (60%) of cells positive to the nick translation in s pecimens treated for 6 h, decreasing to 40% in samples treated for 24 h, when most of the cells were in late apoptosis, In addition, no subd iploid peak was evident in flow cytometry regardless of the time of in cubation with TNF. Our study on Daudi cells clearly supports the exist ence of alternative forms of apoptosis in which DNA degradation does n ot result only in oligonucleosomal fragmentation. (C) 1997 Academic Pr ess Limited.