Cyclosporin A and rapamycin are each used as T cell immunosuppressants. They share the property of binding to immunophilin molecules in T cells as the initial step in their mechanisms of action....

Cyclosporin A and rapamycin are each used as T cell immunosuppressants. They share the property of binding to immunophilin molecules in T cells as the initial step in their mechanisms of action. However, in the case of cyclosporin A, the drug:immunophilin complex binds to and inhibits the protein phosphatase calcineurin, whereas the rapamycin:immunophilin complex binds to and inhibitors mTOR. As a consequence,

1. Cyclosporin A, but not rapamycin, blocks cytokine production by T cells.


2. Both cyclosporin A and rapamycin block cytokine production by T cells.


3. Rapamycin, but not cyclosporin A, blocks T cell proliferation.


4. Neither rapamycin nor cyclosporin A block T cell proliferation.


5. Both cyclosporin A and rapamycin inhibit co-stimulatory signaling through CD28 on T cells.