Imatinib inhibits 12F6-induced CD69 and CD25 up-regulation in a dose-dependent manner. Untreated T cells (□) and T cells preincubated with imatinib () at 1, 5, 10, or 25 μM for one hour as indicated and then stimulated for 24 hours with 12F6 at 50 ng/mL. The mean values and standard deviations of 5 independent experiments are shown. (A) Percentage of cells expressing CD69 above isotype control and (B) percentage of cells expressing CD25 above isotype control.