This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunomodulator, Subject name: Pharmacology
Nephrotoxicity is a side effect of one of the following immuno-suppressives - 
Select and explain. 
A. Sirolimus, B. Tacrolimus, C. Mycophenolate mofetil, D. Azathioprine
B: Tacrolimus
Answer: B: Tacrolimus 
Explanation: Ans. is 'b' i.e., Tacrolimus Tacrolimus is an immunosuppressant.Its most common adverse effect is, NephrotoxicityTacrolimus causes dose dependent renal tubular injury and direct renal artery vasospasm (intrarenal vasoconstriction is the pivotal event in the nephrotoxicity caused by Tacrolimus)Comparison of Tacrolimus and CyclosporineIt is not chemically related to cyclosporine but their mechanism of actions are similar i.e., inhibition of calcineurin, which inhibits T cell activation.On weight basis, Tacrolimus is 10-100 times more potent than cyclosporine in inhibiting immune response.Tacrolimus is also more toxic than cyclosporine and likely to be discontinued for adverse effects. The adverse effect seen with tacrolimus is similar to cyclosporine.- Nephrotoxicity and neurotoxicity are the most commonly encountered adverse effects.