Macrophages are phagocytes primarily found in which location?

• A. Lymph nodes
• B. Dermis
• C. Epidermis
• D. Blood plasma

Answer: (A)

Macrophages act as phagocytes that patrol and filter immune threats in the lymphatic system. They reside in lymphoid tissues, especially lymph nodes, where they sample lymph draining from tissues, engulf microbes, and present antigens to lymphocytes to kick off the adaptive response. While there are macrophages in other tissues (like the dermis), and specialized dendritic cells in the epidermis, the lymph node is the primary site tied to their role in phagocytosis of pathogens carried by lymph. They are not resident in blood plasma, since they circulate as monocytes and differentiate into macrophages in tissues.