Question

Which of the following mechanisms do natural killer (NK) cells use to detect and kill virus-infected cells?

1) Release of cytotoxic granules containing perforin and granzymes
2) Binding of activating receptors to ligands on the infected cells
3) Recognition of downregulated MHC class I molecules on infected cells
4) All of the above

Answer 1

NK cells use cytotoxic granules containing perforin and granzymes, bind activating receptors to infected cells, and recognize downregulated MHC class I molecules to detect and kill virus-infected cells. The correct answer is all of the above.

Step-by-step explanation:

Natural killer (NK) cells employ several mechanisms to detect and kill virus-infected cells. Firstly, they release cytotoxic granules containing proteins known as perforin and granzymes. Perforin forms pores in the target cell's membrane allowing granzymes to enter and induce apoptosis. Secondly, NK cells can bind activating receptors to specific ligands on the infected cells. Lastly, these cells can recognize downregulated MHC class I molecules on infected cells, which is a signal that the cell may be compromised. Therefore, the main answer to the question is that all the mechanisms listed are used by NK cells - (4) All of the above.