Which organ in the lymphatic system filters old blood and supports immunity?

• A. Spleen
• B. Pancreas
• C. Liver
• D. Kidney

Answer: (A)

The spleen handles two big roles: cleaning up old red blood cells and supporting immune defense. In the red pulp, aging or damaged red blood cells are removed by macrophages, and their components are recycled. In the white pulp, lymphocytes monitor the blood for pathogens and mount immune responses, producing antibodies when needed. This combination— filtering worn-out blood cells and facilitating immune activity against blood-borne invaders—is unique to the spleen and explains why it’s the correct answer. The pancreas mainly digests food and regulates metabolism, the liver processes metabolism and detoxification with some immune functions but isn’t the primary filter for old blood in the lymphatic system, and the kidneys are focused on filtering blood to make urine.