Transplant Question 17 Instructor

What is the mechanism of action of cyclosporine and tacrolimus?

Cyclosporine and tacrolimus are both calcineurin inhibitors. They first bind to, respectively, cyclophilin or FKBP (FK binding-protein). This drug/protein complex then binds to and inhibits the activity of calcineurin. Calcineurin dephosphorylates a transcription factor called nuclear factor of activated T-cells (NFAT). This prevents NFAT from entering the nucleus and promoting transcription of several cytokines. The most important of these cytokines is IL-2, while others include IL-4, IFN-g and TNF-a. Inhibition of IL-2 and other cytokines leads to downregulation of T cell responses.

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