Regulatory T (Treg) cells counteract the activity of conventional T (Tconv) cells and are essential for prevention of autoimmunity. The balance between Treg and Tconv cells is often disturbed in cancer or autoimmune diseases. To shift this balance to the desired direction, drugs are developed that target immune receptors expressed on Tconv cells. However, these drugs may also target Treg cells. Available data suggest that Treg cells differentially process the signals downstream of their immune receptors. We aim to identify key differences in costimulatory receptor signaling between Treg and Tconv cells, which potentially allows for selective drug targeting.