What is the main function of the lymph nodes?

• A. To filter harmful material out of the lymph fluid
• B. To produce and house lymphocytes and macrophages for immune system function
• C. Both A and B
• D. Neither A nor B

Answer: (C)

Lymph nodes serve two key roles in immune function. First, they filter lymph as it passes through, with resident macrophages and dendritic cells removing debris, pathogens, and other harmful material. This cleansing helps prevent spread of infection. Second, they are active sites where immune cells—lymphocytes (B and T cells) and macrophages—are produced, housed, and activated. Lymphocytes scan for antigens, proliferate, and coordinate responses right in the node, often with macrophages presenting antigens to kick-start the reaction. Because both filtering lymph and hosting/activating immune cells are essential parts of how lymph nodes work, the best answer includes both aspects. If only one function were considered, you’d miss a major piece of how these nodes support immunity.