Sema3A cosignal differentially increases the Fas-mediated caspase activation in cell lines. (A) Jurkat (left) or HUT78 (right) cells were stimulated with 150 ng/mL APO1-1 in the presence of control IgG or Sema3A-Fc (150 ng/mL) for indicated times. Activation of caspase 8 and caspase 3 was analyzed by immunoblotting. The 18-kDa and 17-kDa bands correspond to active cleavage forms of caspase-8 and -3, respectively. The results shown are representative of 3 independent experiments. (B) Jurkat or CEM (type II) cells were incubated for 7 hours as described in panel A with or without zVAD-fmk (20 μM). Cell death was assessed by flow cytometry with propidium iodide.