A white blood cell is a component of blood. While the red blood cells carry oxygen to the organs and the platelets are responsible for clotting blood after an injury, white blood cells help the body defend and heal itself against foreign invaders, such as bacteria, viruses, fungi and parasites.
White blood cells that are produced by marrow inside the bone are called leukocytes. White blood cells that are produced by lymph nodes in the lymphatic system are called lymphocytes.
The lymphatic system consists of organs, ducts and nodes that produce lymphocytes. Lymphatic vessels contain lymphatic fluid filled with lymphocytes. The tonsils, the spleen and the thymus are lymph nodes. The lymphatic system is responsible for screening lymphatic fluid for signs of infection. Lymphatic fluid also contains some of the plasma from blood that has seeped into the cells. The fluid makes its way back to the veins that are closest to the heart.
Leukocytes and lymphocytes do not stay in the blood. They are in the lymphatic system or in tissue most of the time.
There are three types of leukocytes: neutrophils, eosinophils and basophils. Neutrophils attack and digest bacteria. They can survive three to four days, but after they digest bacteria, they die in about 12 hours.
Eosinophils stain parasites and foreign molecules and digest them. The three-week life span of eosinophils includes maturing, working and reaching their intended target. Basophils merely stain molecules, but they are multiplied in the presence of leukemia. Basophils mature and perform their duties for a period of from three days to a week and a half.
Lymphocytes can live for as long as a month. Lymphocytes include B cells that produce antibodies and T cells that protect the body on a cellular level. The life span of B cells ranges from three or four days to up to five weeks. If a T cell has no function other than to travel throughout the body, it can last for months; if it is engaged in a battle with foreign substances, it will last a from a day or two to a week, depending on the circumstances.
According to doctors and authors of the book "Miscarriages Can Be Prevented," lymphocytes can live for many years. Leukocytes and lymphocytes die early when they engage in fighting germs. Those that don't die by destroying germs die by being destroyed by other white blood cells so that new ones can be made.