Which statement about phagosome processing is correct?

Which statement about phagosome processing is correct?

• A. The phagosome uses mitochondria to digest contents.
• B. The phagocyte releases free antibodies to neutralize pathogens.
• C. The phagosome fuses with a lysosome to digest contents, and antigens may be presented via MHC.
• D. Antigen presentation occurs only after cell death.

Answer: (C)

The essential idea is that phagosome processing relies on the phagosome fusing with a lysosome to form a phagolysosome, where ingested material is digested by lysosomal enzymes. This digestion produces peptide fragments that can be loaded onto MHC class II molecules and then displayed on the cell surface to CD4+ T helper cells, linking innate phagocytosis to adaptive immunity. This is how the immune system reveals what it has captured to the rest of the immune system. Why the other statements aren’t correct: mitochondria don’t digest phagosomal contents, so relying on mitochondria is not how phagosome processing works. antibodies are produced by B cells and secreted, not released by phagocytes to neutralize pathogens in this process. antigen presentation can occur while the cell is alive, and phagocytes present peptides via MHC II after phagosome-lysosome processing rather than only after cell death.

The essential idea is that phagosome processing relies on the phagosome fusing with a lysosome to form a phagolysosome, where ingested material is digested by lysosomal enzymes. This digestion produces peptide fragments that can be loaded onto MHC class II molecules and then displayed on the cell surface to CD4+ T helper cells, linking innate phagocytosis to adaptive immunity. This is how the immune system reveals what it has captured to the rest of the immune system.

Why the other statements aren’t correct: mitochondria don’t digest phagosomal contents, so relying on mitochondria is not how phagosome processing works. antibodies are produced by B cells and secreted, not released by phagocytes to neutralize pathogens in this process. antigen presentation can occur while the cell is alive, and phagocytes present peptides via MHC II after phagosome-lysosome processing rather than only after cell death.