Thereafter cells were sedimented at 300 x g for 5 min and resuspended at 3 x 10 6 cells/ml in RPMI-1640 without serum and stimulated with either anti-CD3 (mouse monoclonal, clone OKT3, Sigma-Aldrich, USA) at the indicated concentrations, anti-CD3 with 3% H2O2 (VWR, USA) and 3% H2O2 for 2 min at 37°C. To find out the optimal stimulation, cells were also stimulated with sodium orthovanadate (Sigma-Aldrich, Sweden) and sodium orthovanadate with 3% H2O2