Tregs, which specifically express the transcription factor forkhead box P3 (FoxP3), are critical for the maintenance of self-tolerance and play an important role in controlling immune responses of effector T-cells to auto and foreign antigens; they prevent a wide range of clinical conditions such as organ-specific autoimmune diseases, and control anti-tumor responses, anti-viral responses, and immune responses to alloantigens in the setting of organ transplantation [3,4]. The gene discussed is FOXP3; the disease is neoplasm.