This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
Immunity against cancer cells 
Select and explain. 
A. Basophil, B. Eosinophils, C. NK cells, D. Neutrophil
C: NK cells
Answer: C: NK cells 
Explanation: Ref Robbins 8/EP 188;9/e p192 NK cells kill virus- infected cells and produce the macrophage-activating cyto- kine IFN-g. If the microbes enter the blood, many plasma proteins, including the proteins of the complement system, recognize the microbes and are activated, and their products kill microbes and coat (opsonize) the microbes for phagocytosis. In addition to combating infections, innate immune responses stimulate subsequent adaptive immu- nity, providing signals that are essential for initiating the responses of antigen-specific T and B lymphocytes.