Imatinib inhibits 12F6-induced IL-2 production. Untreated CD3⁺ T cells (□) and CD3⁺ T cells pretreated with 10 μM imatinib (▦) for one hour were incubated for 24 hours either unstimulated or stimulated with 12F6 (100 ng/mL), with or without activation of costimulatory receptors using antibodies against CD28 and CD49d at 1 μg/mL (CM). Means for T cells from one donor assayed in triplicate are shown with standard deviation. Comparable results were obtained in a second donor.