What is a primary function of the lymphatic system in immunity?

• A. Transport of lymph and immune cells, with defense via lymph nodes and immune surveillance
• B. Filter blood to remove pathogens
• C. Produce red blood cells
• D. Regulate blood pressure

Answer: (A)

The lymphatic system’s main role in immunity is to move lymph and immune cells through an extensive network of vessels and to use lymph nodes as immune surveillance stations. As tissue fluid becomes lymph, it carries antigens and antigen-presenting cells to lymph nodes. In these hubs, T cells and B cells can encounter antigens and mount targeted immune responses, while macrophages and dendritic cells help present those antigens. This setup provides constant immune surveillance and rapid defense against pathogens, which is exactly what the option describes: transport of lymph and immune cells with defense via lymph nodes and immune surveillance.

Other options miss the primary immune function. Filtering blood to remove pathogens is more characteristic of the spleen and liver, producing red blood cells happens in bone marrow, and regulating blood pressure is a cardiovascular/physiological task not specific to lymphatic immunity.