This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunomodulators, Subject name: Pharmacology
Tacrolimus acts by inhibiting: 
Select and explain. 
A. DNA and RNA synthesis, B. Anti-lymphocyte antibody formation, C. T-Cell proliferation, D. All of the above
C: T-Cell proliferation
Answer: C: T-Cell proliferation 
Explanation: Tacrolimus (FK506) It is a newer immunosuppressant chemically different from cyclosporine, but having the same mechanism of action, and is -100 times more potent. It binds to a different cytoplasmic immunophilin protein labeled 'FKBP', but the subsequent steps are the same, i.e. inhibition of helper T cells calcineurin. Tacrolimus is administered orally as well as by i.v. infusion. Oral absorption is variable and decreased by food. It is metabolized by CYP3A4 Section 14 and excreted in bile with a longer tlh of 12 hour. It is paicularly valuable in liver transplantation because its absorption is not dependent on bile. Because of more potent action, it is also suitable for suppressing acute rejection that has set in. Hypeension, hirsutism and gum hyperplasia are less marked than cyclosporine, but tacrolimus is more likely to precipitate diabetes, cause neurotoxicity, alopecia, and diarrhea. Dose-limiting toxicity is renal. ESSENTIALS of MEDICAL PHARMACOLOGY SIXTH EDITION -K. D TRIPATHI Page:853