What is the function of the lymph nodes within the lymphatic system?

• A. Filter lymph and mount immune responses
• B. Produce hormones
• C. Filter blood
• D. Store minerals

Answer: (A)

Lymph nodes primarily filter lymph and help start and coordinate immune responses. As lymph—the fluid that drains tissues—flows through a node, macrophages and other immune cells inspect it, catching pathogens and debris. If a threat is detected, the nodes activate lymphocytes, leading to antibody production by B cells and targeted responses by T cells. This dual role of cleansing lymph and triggering adaptive immunity is what lymph nodes do best. Hormones are produced by endocrine glands, not lymph nodes; filtering blood is the job of organs like the spleen and liver; and minerals are stored mainly in bones.