White blood cell
noun, plural: white blood cells
Any of the blood cells that lack hemoglobin, colourless and with nucleus. Its primary role involves the body's immune system, protecting the body against invading microorganisms and foreign particles.
White blood cells include the lymphocytes, macrophages, monocytes and granulocytes. Elevated counts of white blood cells indicate inflammation or infection. In adult humans, the normal range of white blood cell counts is 4500 to 11 000 per mm3.
The name, white blood cell, originates from the fact that centrifugation of blood sample results in the formation of a thin layer of cells which are generally white in color between the sedimented red blood cells and the blood plasma.