Leukocytes, or white blood cells, are clear or whitish colored cells that lack hemoglobin but have a nucleus. Leukocytes protect the body against invading microorganisms and remove dead cells and debris from the body. Most leukocytes are motile, exhibiting ameboid movement, which is the ability to move like an amoeba by putting out irregular cytoplasmic projections. Leukocytes leave the circulation and enter tissues by diapedesis, a process in which they become thin and elongated and slip between or, in some cases, through the cells of blood vessel walls.
