This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunity, Subject name: Pathology
[{'content': 'Not true regarding NK cells is? \nSelect and explain. \nA. Active against malignant cells, B. Involve MHC antigen for killing micro-organisms, C. First line defense against viral infections, D. No prior sensitization required', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) Involve MHC antigen for killing microorganisms (Ref: Robbins 9th/pg 192; 8th/pg 188)Natural Killer Cells Destroy virus-infected cells and tumor cells without prior exposure;NK cells do not require MHC for killing micro-organismsSurface molecules of NK cells are CD16 & CD56', 'role': 'assistant'}]