White Blood Cells & Granulocytes

White Blood Cells

White blood cells (leukocytes) are one of the body’s defenses against disease. Some white cells travel throughout the body and destroy bacteria, some produce antibodies against bacteria and viruses, and others help fight malignant diseases. One’s own “leukocytes” help maintain the body’s immune function, but when present in donated blood, they serve no purpose. In fact, leukocytes may carry viruses that cause immune suppression and release toxic substances in the recipient. Leukocytes can cause a reaction when transfused, and are often removed from the transfusable blood components, a process called leuko-reduction. The majority of white blood cells are produced in the bone marrow, where they outnumber red blood cells by 2 to 1. However, in the blood stream, there are about 600 red blood cells for every white blood cell. There are several different types of white blood cells.


Granulocytes are one type of several types of white blood cells that are in fact used in more specialized transfusion therapy. Granulocytes and monocytes protect against infection by surrounding and destroying invading bacteria and viruses, and lymphocytes aid in the immune defense system. Granulocytes are prepared by an automated process called apheresis, and must be transfused within 24 hours after collection. They are used for infections that are unresponsive to antibiotic therapy.

See Summary of Transfusable Blood Components »