Question

Which of the following is NOT a mechanism of action of cyclosporine leading to immunosuppression?

• A. Inhibition of transcription of IL-2 gene
• B. Inhibition of Calcineurin pathway
• C. Inhibition of Cytochrome P450 3A4
• D. Inhibition of dephosphorylation of NF-AT

Hint:

Cyclosporine suppresses immune responses by inhibiting calcineurin, preventing NF-AT activation, and reducing IL-2 production.

Answer 1

The Correct Option is C

Step 1: Understanding Cyclosporine's Mechanism 
Cyclosporine is an immunosuppressive drug that inhibits T-cell activation by binding to cyclophilin, which then inhibits calcineurin, preventing NF-AT dephosphorylation. 
Step 2: Evaluating the Options 
- Inhibition of transcription of IL-2 gene: True, cyclosporine inhibits IL-2 transcription, which is crucial for T-cell activation. 
- Inhibition of Calcineurin pathway: True, cyclosporine inhibits calcineurin, blocking T-cell activation. 
- Inhibition of Cytochrome P450 3A4: Incorrect, cyclosporine inhibits cytochrome P450 3A4 (not a mechanism of immunosuppression, but affects drug metabolism). 
- Inhibition of dephosphorylation of NF-AT: True, cyclosporine prevents NF-AT activation by inhibiting calcineurin. 
Step 3: Conclusion 
Cyclosporine does not inhibit Cytochrome P450 3A4 as a mechanism of immunosuppression.