CD28 and hemolytic-uremic syndrome: Belatacept is a selective costimulation blocker that binds CD80 and CD86, thereby blocking CD28-mediated costimulation in the T-cell activation cascade.3,4 We present a case of a lung transplant recipient who developed hemolytic uremic syndrome (HUS) secondary to tacrolimus and subsequently sirolimus, who was ultimately switched to belatacept.