Which statement best describes phagocytosis?

• A. The targeted killing of pathogens by cytotoxic T-cells
• B. The release of histamines to promote inflammation
• C. The production of antibodies by B-cells
• D. The non-specific ingestion and digestion of pathogens by phagocytes such as macrophages and neutrophils

Answer: (D)

Phagocytosis is an innate, non-specific defense where specialized white blood cells called phagocytes—such as macrophages and neutrophils—engulf and digest invading pathogens. This process does not require prior exposure to the pathogen, making it a first-line defense. The phagocyte recognizes and binds to the pathogen, engulfs it to form a phagosome, then fuses with a lysosome to create a phagolysosome where enzymes break down the ingested material. The key idea is the non-specific ingestion and digestion by phagocytes. The other statements describe different immune functions: cytotoxic T-cells kill infected host cells, histamines promote inflammation, and B-cells produce antibodies.