|white blood cell (wīt) Pronunciation Key
Any of various white or colorless cells in the blood of vertebrate animals, many of which participate in the inflammatory and immune responses to protect the body against infection and to repair injuries to tissues. White blood cells are formed mainly in the bone marrow, and unlike red blood cells, have a cell nucleus. The major types of white blood cells are granulocytes, lymphocytes, and monocytes. White blood cells are far less numerous in the blood than red blood cells, but their amount usually increases in response to infection and can be monitored as part of a clinical assessment. Also called leukocyte.