The spleen contributes to immunity by:

• A. Digesting fats
• B. Regulating blood sugar
• C. Filtering blood and fighting bacteria
• D. Producing red blood cells

Answer: (C)

The spleen helps immunity by filtering the bloodstream and mounting responses to pathogens carried in the blood. In its immune areas, lymphocytes recognize antigens and help produce antibodies, while macrophages in the spleen phagocytose bacteria and clear old or damaged cells from circulation. This combination makes the spleen an important site for guarding against blood-borne infections, especially from bacteria. Fat digestion is handled by the digestive system, not the spleen; regulating blood sugar is mainly a function of the liver and pancreas; and red blood cell production occurs primarily in the bone marrow (with the spleen playing a role only in certain conditions, not as its normal function).