Sirolimus provides immunosuppression in renal transplantation through which molecular action?

• A Inhibition of calcineurin phosphatase activity
• B Antagonism of the IL-2 receptor CD25 on activated T cells
• C Inhibition of IMP dehydrogenase in the de novo purine pathway
• D Blockade of IL-2 signal transduction via inhibition of mTOR kinase ✓

Explanation

Sirolimus binds FKBP-12 but, unlike tacrolimus, does not inhibit calcineurin; the complex blocks mTOR, preventing IL-2 driven progression of the T cell from G1 to S phase. Option B describes basiliximab, an anti-CD25 monoclonal antibody, and option C describes mycophenolate, making these the two best distractors because all three act downstream of IL-2 or purine synthesis in T cell proliferation.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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