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
N.K. cell and cytotoxic cells are differentiated by ? 
Select and explain. 
A. Interferons reduce N.K. cell activity, B. Antibody specificity, C. Receptor for IgG, D. Presence in spleen
B: Antibody specificity
Answer: B: Antibody specificity 
Explanation: Ans. is 'b' i.e., Antibody specificity . Cytotoxicity of NK cells is not antibody dependent or MHC restricted, while cytotoxic cells are capable of lysing or killing target cells sensitized with antibody.