Blood cell that is colorless, lacks hemoglobin, and contains a nucleus. Leukocytes are involved with host defense and are classified in two large groups: granular leukocytes (basophils, eosinophils, and neutrophils) and nongranular leukocytes (lymphocytes and monocytes). Called also white blood cell.

White blood cell (WBC). There are five types of leukocytes: three granulocytes with granules in die cytoplasm—neutrophils, basophils, and eosiniphils—and two agranulocytes, lacking granules in the cytoplasm—lymphocytes and monocytes. An important part of the body’s defense mechanism, leukocytes phagocytose (engulf and digest) bacteria and fungi and function in allergic reactions and the response to cellular injury. Also called white blood cell; white corpuscle.

White blood cells including the five subtypes: lymphocytes, monocytes, neutrophils, basophils, and eosinophils; normal blood values range from 5,000 to 10,000 per cubic millimeter.

A blood cell that helps fight infection; also called a white blood cell. Any blood cell that contains a nucleus is a leukocyte. Leukocytes are capable of moving independently, as when they travel through blood vessel walls to a wound site to protect the body against foreign substances. Leukocytes are able to engulf foreign particles, such as bacteria, and this process causes an increase in the number of leukocytes in the blood during infection. Laboratory testing to determine whether infectious disease is present is based on the number of leukocytes in the blood.

Any blood cell that contains a nucleus. In health there are three major subdivisions: granulocytes, lymphocytes and monocytes, which are involved in protecting the body against foreign substances and in antibody production. In disease, a variety of other types may appear in the blood, most notably immature forms of the normal red or white blood cells.

There are two types: granulocytes (those possessing, in their cytoplasm, large granules that stain different colors under a microscope) and. agranulocytes (those lacking granules). Granulocytes include basophils, eosinophils, and neutrophils. Agranulocytes include monocytes and lymphocytes. Clinically, granulocytes are often referred to as “polys” because they are all polymorphonuclear (multilobed nuclei); whereas agranulocytes are mononuclear (one nucleus).

A type of blood cell known as a white blood cell plays a vital role in defending the body against infections and combating them when they arise. They are larger in size compared to red blood cells.

A type of white blood cell. There exist several types of leukocytes, each distinguishable from the others when viewed under a microscope based on their unique staining reactions.