Cyclosporine interferes with the production of cytokines and lacks the bone marrow toxicity of azathioprine. Unfounately, its chief toxicity is renal. Although OKT3 is more available, more uniform, and more specific than antilymphocyte serum, some of its side effects are even greater, such as fever, chills, nausea, vomiting, diarrhea, and pulmonary edema. Tacrolimus has been used most extensively for liver grafts. It has been found especially valuable in reversing rejection of failing grafts.