(A) Jurkat T cells, which constitutively express TRAILshort, were induced to die by the addition of sk-TRAIL, in the presence or absence of increasing amounts of anti-TRAILshort antibody. Cell death was measured by active caspase 3 staining. Control cells were treated with increasing anti-TRAILshort antibody alone. (B) Jurkat T cells, which do not express TRAILshort, were stimulated to die by the addition of sk-TRAIL in the absence or presence of increasing amounts of a fusion protein consisting of the extracellular domain of TRAILshort fused to Fc (TRAILshort-ECD:Fc) or with bovine serum albumin (BSA) control and analyzed as in (A). Additional control cells were treated with increasing TRAILshort-ECD:Fc alone. Data are representative of six independent experiments. P<0.05 considered statistically significant (linear regression).