Mature Lymphocyte

**Semantic type:** Cell

**Definition:** A white blood cell that matures in the primary lymphoid organs and then circulates through the lymph system to the secondary lymphoid tissues where it interacts with antigens. A mature lymphocyte varies in size from 7 to 15 micrometer in diameter and is round or ovoid, but may be notched or slightly indented. The chromatin is generally diffusely dense and nucleoli are not usually visible.