What is the role of calcineurin inhibitors in immunosuppressive therapy?

• A. They prevent activation of lymphocytes involved in rejection
• B. They activate B cells to fight infection
• C. They enhance antibody production
• D. They only work in autoimmune diseases

Answer: (A)

The main concept is that calcineurin inhibitors suppress the cell-mediated immune response by blocking T-cell activation. They do this by inhibiting calcineurin, a phosphatase that normally dephosphorylates NFAT. When NFAT is dephosphorylated, it enters the nucleus and drives transcription of interleukin-2, a key T-cell growth signal. By blocking calcineurin (with drugs like cyclosporine or tacrolimus), IL-2 production drops, and T lymphocytes don’t proliferate as they would after antigen exposure. This effectively reduces the T-cell–mediated attack on a transplanted organ, lowering the risk of rejection.

These drugs don’t activate B cells or boost antibody production, and their use isn’t limited to autoimmune diseases—they’re foundational in preventing graft rejection and are also used in some autoimmune conditions. They also require careful monitoring due to potential nephrotoxicity and other side effects.