Which drug has T-lymphocyte suppressive activity and is used as a cytotoxic therapy option?

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

Answer: (A)

Cyclosporine is a targeted immunosuppressant that specifically dampens T-lymphocyte activity. It binds to cyclophilin and inhibits calcineurin, which prevents the dephosphorylation and activation of the transcription factor NFAT. Without NFAT activation, interleukin-2 (IL-2) production drops, so T cells cannot proliferate effectively. This selective suppression of T-cell activation is why cyclosporine is described as having T-lymphocyte–suppressive activity and is used as a cytotoxic therapy option in settings where reducing T-cell–mediated immune responses is crucial, such as transplant immunosuppression and certain autoimmune conditions.

In contrast, the other options are more broadly cytotoxic. Chlorambucil and cyclophosphamide are alkylating agents that damage DNA across many cell types, not just T cells. Azathioprine inhibits purine synthesis and broadly suppresses lymphocyte proliferation but does not selectively target T-cell activation in the same way cyclosporine does.