This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basic Concepts, Subject name: Pathology
Mixed lymphocyte culture is useful for identification of which of the following cells? 
Select and explain. 
A. MHC class I antigen, B. MHC class II antigen, C. B lymphocytes, D. Natural killer cells
B: MHC class II antigen
Answer: B: MHC class II antigen 
Explanation: MHC class I antigen are expressed on all nucleated cells and platelets. Technique by which we detect the presence of MHC Class I antigen is alloantisera. MHC class II antigens are expressed on the surface of all APC's. (Antigen Presenting Cells). Technique by which we detect the presence of MHC class II antigen is Mixed lymphocyte culture. The genes encoding MHC molecules are clustered on a small segment of chromosome 6.