Which structure contains lymph and immune cells within the lymphatic system?

• A. Spleen
• B. Lymph nodes
• C. Liver
• D. Thymus

Answer: (B)

Lymph nodes are the hubs along lymph vessels where lymph is filtered and immune cells are concentrated. As lymph flows into a node, macrophages and dendritic cells process pathogens and present antigens to B and T lymphocytes, allowing the immune system to respond if needed. This combination of circulating lymph and resident immune cells makes lymph nodes the primary structure in the lymphatic system that contains both. Structures like the spleen also have immune cells but they filter blood rather than lymph; the thymus is involved in T cell development, not in filtering lymphflow; and the liver isn’t a lymph-transport structure.