Cyclosporin A is used in transplant patients mainly because it does what?

• A. Prevents infections
• B. Suppresses the recipient's immune response against the transplant
• C. Kills transplanted tissue's immune cells
• D. Increases B cell numbers

Answer: (B)

The main idea is that preventing graft rejection relies on dampening the recipient’s T-cell–mediated immune response. Cyclosporin A inhibits a key T-cell signaling pathway (calcineurin), which reduces production of interleukin-2 and other cytokines. Without these signals, T cells don’t become activated or proliferate, so the immune attack on the transplanted tissue is minimized. This makes the transplant less likely to be rejected.

It doesn’t prevent infections directly; in fact, immunosuppressants can raise infection risk. It also doesn’t kill immune cells living in the transplanted tissue, but rather prevents their activation. And it doesn’t increase B cell numbers; its primary effect is on T cells, which are the main drivers of acute graft rejection.