(a) Ukrain-induced apoptosis depends on caspase-activation. Jurkat A3 cells were pre-incubated for 2 h with medium supplemented with 30 μM of the pan-caspase-inhibitor zVAD-fmk or left untreated. Subsequently, cells were treated for 24 h with medium or 10 μg/ml Ukrain. Apoptosis was then quantified by counting of the cells with apoptotic nuclear morphology (left panel). Data show means ± SD, n = 3. Paired t-test was performed using GraphPad InStat version 3.00 for Windows 95, GraphPad Software, San Diego California USA, http://www.graphpad.com. Micrographs showing reduced induction of apoptotic nuclear morphology upon combined treatment are depicted in the right panel. (b) Ukrain exerts concentration- and time-dependent cytotoxic effects on Jurkat T-lymphoma cells. Jurkat Vector cells were treated for 24 h with medium, 5, 10 and 50 μg/ml Ukrain (left panel) or for 0, 12, 24 or 48 h with 10 μg/ml Ukrain (right panel). The number of living and dead cells was then quantified by light microscopy using Trypan Blue Exclusion. Data show means ± SD, n = 3.