What is the main function of lymph nodes?

The correct answer is Option (3) → Trapping microorganisms or antigens

Lymph nodes are small solid structures located at different points along the lymphatic system. They hold back micro-organisms or other antigens that get into the lymph and tissue fluid. The trapped antigens activate the lymphocytes present there and cause the immune response.

Option (1) Production of lymphocytes — Incorrect. All blood cells, including lymphocytes, are produced in the bone marrow, not in the lymph nodes.

Option (2) Maturation of T-lymphocytes — Incorrect. T-lymphocytes develop and mature in the micro-environments of the bone marrow and the thymus, the primary lymphoid organs.

Option (3) Trapping microorganisms or antigens — Correct. Trapping micro-organisms or antigens from the lymph and tissue fluid is the function of lymph nodes.

Option (4) Filtering the blood — Incorrect. The spleen acts as a filter of the blood by trapping blood-borne micro-organisms. Lymph nodes act on lymph, not on blood.

NCERT Extract:
Immune System in the Body – “… The spleen is a large bean-shaped organ. It mainly contains lymphocytes and phagocytes. It acts as a filter of the blood by trapping blood-borne microorganisms. Spleen also has a large reservoir of erythrocytes. The lymph nodes are small solid structures located at different points along the lymphatic system. Lymph nodes serve to trap the micro-organisms or other antigens, which happen to get into the lymph and tissue fluid. Antigens trapped in the lymph nodes are responsible for the activation of lymphocytes present there and cause the immune response.”