Which cell type is primarily responsible for clearing inhaled debris in the alveolar space?

• A. Alveolar macrophages decrease in number
• B. Alveolar macrophages produce surfactant
• C. Alveolar macrophage phagocytosis decreases
• D. Alveolar macrophages aggregate to clear debris

Answer: (D)

Alveolar macrophages are the resident immune cells in the air sacs of the lungs that clear inhaled debris through phagocytosis. They patrol the alveolar space and cluster around and ingest particulate matter, earning the nickname “dust cells.” This debris-clearing function is their primary role, distinct from surfactant production by type II pneumocytes and from any reduction in their numbers. So, the idea that alveolar macrophages aggregate to clear debris best describes how the lungs remove inhaled material from the alveolar space.