Assertion (A): Spleen acts as a filter of blood by trapping blood borne microorganisms.
Reason (R): Spleen has a large reservoir of erythrocytes.

The spleen is a large bean-shaped organ. It mainly contains lymphocytes and phagocytes. The red pulp of the spleen is made up of cords of connective tissue and blood sinusoids. Blood is filtered through gaps in the sinusoid lining, which prevents old, damaged or abnormal red blood cells from passing into the bloodstream. These unwanted cells are targeted by phagocytes. The phagocytes also ingest any invading pathogens. Thus, spleen acts as a filter of blood by trapping blood-borne microorganisms. The antigens of pathogens are recognised by lymphocytes of the spleen.