What is the role of lymph nodes in immune defense?

• A. They filter pathogens and present antigens.
• B. They produce red blood cells.
• C. They store calcium.
• D. They are irrelevant to immune defense.

Answer: (A)

Lymph nodes act as immune surveillance hubs where lymph fluid is filtered and immune cells sample for invading pathogens. When antigens arrive, dendritic cells and macrophages capture them and present fragments to T cells inside the node. This antigen presentation activates T cells and helps B cells mature into antibody-producing cells, coordinating the adaptive response. The node’s organized regions and germinal centers support these interactions, boosting specificity and memory for future encounters. Red blood cell production happens in bone marrow, calcium storage occurs in bone tissue, and lymph nodes are not irrelevant to immune defense; they are central to detecting and orchestrating immune responses.