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
Graft versus host reaction is caused by 
Select and explain. 
A. B-Lymphocytes, B. T-lymphocytes, C. Monocytes, D. Leukocytes
B: T-lymphocytes
Answer: B: T-lymphocytes 
Explanation: None