NK cells induce apoptosis in virally infected cells by secreting which protein-degrading enzymes?

• A. Lysozymes
• B. Proteasomes
• C. Granzymes
• D. Caspases

Answer: (C)

Verified step by step guidance

1. Understand the role of NK (Natural Killer) cells in the immune system. NK cells are a type of lymphocyte that play a critical role in the innate immune response by targeting virally infected cells and tumor cells.
2. Learn about apoptosis, which is a programmed cell death mechanism. NK cells induce apoptosis in infected cells to prevent the spread of viruses.
3. Identify the key molecules involved in the process. NK cells release perforins, which create pores in the target cell membrane, allowing other molecules to enter the cell.
4. Focus on granzymes, which are serine proteases secreted by NK cells. Granzymes enter the target cell through the pores created by perforins and trigger the apoptotic pathway by activating caspases, which are enzymes responsible for dismantling the cell.
5. Clarify why other options are incorrect: Lysozymes are enzymes that break down bacterial cell walls, proteasomes degrade proteins within cells, and caspases are downstream enzymes activated during apoptosis but are not secreted by NK cells.