Which of the following act through helper T cells?: (A) Cyclosporine, (B) Azathioprine, (C) Cytarabine, (D) Cycloserine
Answer is A. Mechanism of action of:

Cyclosporine - Through T helper cells (by inhibiting calcineurin)
Azathioprine - Inhibits de novo purine synthesis and damages DNA. It selectively affects cytolytic T lymphocytes.
Cytarabine - Inhibits DNA synthesis in S-phase.
Cycloserine - Inhibits bacterial cell wall synthesis.