This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Which of the following act through helper T cells? 
Select and explain. 
A. Cyclosporine, B. Azathioprine, C. Cytarabine, D. Cycloserine
A: Cyclosporine
Answer: A: Cyclosporine 
Explanation: 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.