Pus is composed of which components?

• A. White blood cells, bacteria, and dead cells
• B. White blood cells only
• C. Bacteria and red blood cells
• D. White blood cells and red blood cells

Answer: (A)

During an infection, pus forms as part of the inflammatory response. White blood cells, especially neutrophils, rush to the site to attack invading bacteria. Many of these immune cells die after fighting, and their remnants mix with bacteria and debris from damaged tissue, creating the creamy, yellowish material we call pus. So the best answer reflects all three components of pus: white blood cells, bacteria, and dead cells.

White blood cells alone misses the bacteria and debris that are also present; bacteria and red blood cells aren’t defining components of pus—red blood cells would indicate bleeding rather than the purulent material produced by infection.