CD4+CD25+ regulatory T cells (Tregs) can influence various immune responses. 
Little is known about the effects of the Abl/Src kinase inhibitor dasatinib on 
Tregs which regulate anti-tumor/leukaemia immune responses. The present study 
demonstrated that dasatinib inhibited proliferation of Tregs and CD4+CD25- T 
cells in a dose-dependent manner, which was associated with the decreased 
production of corresponding cytokines. Treatment of Tregs with dasatinib 
inhibited the suppressive capacity of Tregs. The mechanisms of this inhibition 
included arrest of cells in the G0/G1 phase of cell cycle, down-regulation of 
the transcription factor forkhead box P3, glucocorticoid-induced tumour necrosis 
factor receptor and the cytotoxic T lymphocyte associated protein 4 as well as 
inhibition of signaling events through Src and nuclear factor kappaB. Dasatinib 
showed an inhibitory effect on the proliferation and function of both Tregs and 
CD4+CD25- T cells at therapeutically relevant concentrations of the drug. 
Clinical administration of dasatinib might influence not only the 
graft-versus-leukaemia effect but also the graft-versus-host-disease in patients 
receiving dasatinib after allogeneic stem cell transplantation and/or donor 
lymphocytes infusion as the function of both Tregs and effector T cells are 
hampered in a similar way by dasatinib.