A male client received a heart-lung transplant 1 month ago at a local transplant center. While visiting the nursing center to have his blood pressure taken, he complains of recent weakness and fatigue. He also tells the nurse that he is considering stopping his cyclosporine because it is expensive and is causing his face to become round. He fears he will catch viruses and be more susceptible to infections. The nurse responds to this last statement by explaining that cyclosporine: