All white blood cells are produced and derived from multipotent cells in the bone marrow known as hematopoietic stem cells. Leukocytes are found throughout the body, including the blood and lymphatic system.

Where are most leukocytes located?

Most leukocytes have a relatively short lifespan, typically measured in hours or days. Production of all leukocytes begins in the bone marrow under the influence of CSFs and interleukins. Secondary production and maturation of lymphocytes occurs in specific regions of lymphatic tissue known as germinal centers.

Are leukocytes found in the bloodstream?

White blood cells (leukocytes), unlike red cells, are nucleated and independently motile. Highly differentiated for their specialized functions, they do not undergo cell division (mitosis) in the bloodstream, but some retain the capability of mitosis.