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: Microbiology
NK cells activity is enhanced by - 
Select and explain. 
A. IL-1, B. TNF, C. IL-2, D. TGP-β
C: IL-2
Answer: C: IL-2 
Explanation: IL-2 acts as a growth factor for N K cells.