Question

The two older cytotoxic drugs most commonly used for immunosuppression are cyclophosphamide and azathioprine. These have many toxic effects on tissues in the body. There are now less toxic alternatives that are products from bacteria and fungi, including cyclosporin A and tacrolimus, which are used to treat transplant patients. Each binds to a different group of immunophilins, or peptidyl-prolyl isomerases. The immunophilin drug complexes bind and inhibit what serine/threonine phosphatase?

Calcineurin
Caspase
Chlorambucil
Concanavalin A
Urease

Answer 1

Cyclosporin A and tacrolimus are immunosuppressive drugs that bind to immunophilins to form complexes that inhibit the serine/threonine phosphatase calcineurin, a critical enzyme in T-cell activation.

Step-by-step explanation:

The immunosuppression drugs cyclosporin A and tacrolimus are less toxic alternatives to the older cytotoxic drugs used for this purpose, such as azathioprine and cyclophosphamide. Cyclosporin A and tacrolimus operate by binding to specific immunophilins, and the resulting complexes bind to and inhibit a serine/threonine phosphatase known as calcineurin. This inhibition is significant because calcineurin is crucial for T-cell activation and, therefore, for initiating an immune response which includes the production of interleukins. Hence, by inhibiting calcineurin, these drugs prevent the proliferation of T cells, achieving the goal of immunosuppression needed to prevent organ transplant rejection.