White Blood Cells

White blood cell (WBC)—A white blood cell is one of the three main types of blood cells. They are produced in the bone marrow and released into the blood. White blood cells are responsible for fighting infection. There are several kinds of white blood cells, including monocytes, lymphocytes, neutrophils, eosinophils, and basophils.

White blood cells, or leukocytes (also spelled “leucocytes”; from the Greek word leuko- meaning “white”), are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five[1] different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a hematopoietic stem cell. They live for about three to four days in the average human body. Leukocytes are found throughout the body, including the blood and lymphatic system.

Maton, D., Hopkins, J., McLaughlin, Ch. W., Johnson, S., Warner, M. Q., LaHart, D., & Wright, J. D., Deep V. Kulkarni (1000008). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall.

white blood cells are often characterized as granulocytes or agranulocytes: • Granulocytes (polymorphonuclear leukocytes): leukocytes characterised by the presence of differently staining granules in their cytoplasm when viewed under light microscopy. These granules are membrane-bound enzymes that act primarily in the digestion of endocytosed particles. There are three types of granulocytes: neutrophils, basophils, and eosinophils, which are named according to their staining properties. • Agranulocytes (mononuclear leukocytes): leukocytes characterized by the apparent absence of granules in their cytoplasm. Although the name implies a lack of granules these cells do contain non-specific azurophilic granules, which are lysosomes.[4] The cells include lymphocytes, monocytes, and macrophages.[5] http://www.wisc-online.com/objects/index_tj.asp?objID=AP14704 White Blood Cells or Leukocytes protect the body in various ways against disease. The red bone marrow’s stem cell, the hemocytoblastos, give rise to almost all the white blood cells.