What is the preferred cytotoxic drug due to T-lymphocyte specific activity?

• A. Cyclosporine
• B. Azathioprine
• C. Chlorambucil
• D. Cyclophosphamide

Answer: (A)

T-lymphocyte targeted immunosuppression is best achieved with a calcineurin inhibitor that specifically blocks T-cell activation. Cyclosporine binds to cyclophilin, forming a complex that inhibits calcineurin. This prevents dephosphorylation of NFAT, so IL-2 transcription doesn’t occur and T-cell proliferation is markedly reduced. Because the key problem in many T-cell–driven GI inflammatory processes is the activity of T cells, this mechanism provides effective control with relatively selective impact on T cells.

Azathioprine is an antimetabolite that broadly inhibits lymphocyte proliferation by disrupting purine synthesis, affecting multiple immune cells and usually taking longer to become evident. Chlorambucil and cyclophosphamide are alkylating agents that damage DNA in rapidly dividing cells across the board, leading to widespread cytotoxicity and more systemic side effects. Their lack of T-cell specificity makes them less ideal when the goal is targeted T-cell suppression.

So the drug that best fits a T-lymphocyte–specific mechanism is cyclosporine.