Final answer:
The assertion that macrophages come from monocytes is true. These cells are critical to the immune system, responsible for ingesting pathogens and signaling other immune cells to areas of infection.
Step-by-step explanation:
The statement that macrophages are derived from monocytes is true. Monocytes are a type of white blood cell that circulates in the blood and lymphatic system. They originate from myeloid stem cells and typically account for 2-8 percent of the total leukocyte count. Once they move into infected tissue, monocytes differentiate into macrophages. These macrophages are critical components of the immune system, phagocytizing debris, foreign pathogens, worn-out erythrocytes, and many other dead or damaged cells. Macrophages also release antimicrobial defensins and chemotactic chemicals, which attract other leukocytes to the site of infection. While some macrophages are fixed and reside within certain tissues, others are free to roam the tissue fluid to fight infections.