How do calcineurin inhibitors such as cyclosporine affect T cells?

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Kidney transplant — transplant British surgeon Andrew Ready flushing a donated kidney during a transplant at Queen Elizabeth Hospital, Birmingham, England, 2006.

In the context of transplant surgery, calcineurin inhibitors such as cyclosporine function as potent immunosuppressants by targeting the intracellular signaling pathways required for the activation of T cells.1

By inhibiting the enzyme calcineurin, these drugs effectively suppress the normal function of T cells—a type of white blood cell responsible for identifying and eliminating foreign molecules. This inhibition is critical in preventing the immune system from attacking and rejecting transplanted organs. Because T cells are central to the body's rejection response, blocking their activation helps ensure the survival of the graft in patients undergoing procedures such as kidney, liver, or heart transplantation.1