Which of the following is an oxygen-dependent killing mechanism used by phagocytes?

• A. Release of lysozyme
• B. Secretion of defensins
• C. Production of reactive oxygen species (ROS) such as superoxide anion (O_2^-)
• D. Acidification of the phagolysosome

Answer: (C)

Verified step by step guidance

1. Understand that phagocytes kill microbes using two main types of mechanisms: oxygen-dependent and oxygen-independent.
2. Recall that oxygen-independent mechanisms include the release of enzymes like lysozyme and secretion of antimicrobial peptides such as defensins, as well as acidification of the phagolysosome.
3. Recognize that oxygen-dependent killing involves the production of reactive oxygen species (ROS), which are highly reactive molecules that damage microbial components.
4. Identify that reactive oxygen species include molecules like superoxide anion (O\_2^-), hydrogen peroxide (H\_2O\_2), and hydroxyl radicals, which are generated during the respiratory burst in phagocytes.
5. Conclude that among the options, the production of reactive oxygen species (ROS) such as superoxide anion (O\_2^-) is the oxygen-dependent killing mechanism used by phagocytes.