The Probert Encyclopaedia of Medicine

LEUCOCYTES

Leucocytes (white blood cells) are outnumbered by the red blood cells 600 to 1. These cells are spherical in shape and slightly larger than red blood cells. There are five types of leukocytes. Three of the five have a granular appearance. These are the neutrophils, eosinophils, and the basophiles. The other two, the lymphocytes and monocytes, have smooth, non-granular bodies. The main function of the leukocytes is to provide a defence against 'foreign' material (infectious agents, foreign bodies, abnormal proteins). In the presence of a foreign material, basophiles and some lymphocytes release chemicals that cause inflammation, trapping the invader. The other leukocytes then take the foreign material into their own bodies and digest them. This process of digestion is called phagocytosis. The cells that digest microbes are called phagocytes. The most numerous of the phagocytes are the neutrophils.

In addition to neutrophils, eosinophils, and monocytes, the body has other phagocytes that are not white blood cells. They are classed as reticuloendothelial cells, a type of connective tissue cells. Lymphocytes are the smallest white blood cells and are a part of the immune mechanism. They form antibodies against disease. When microbes invade the body, lymphocytes begin to multiply and they become transformed plasma cells. Each microbe stimulates only one type of lymphocyte to multiply and form one type of plasma cell. The type of plasma cell formed is the type that can make a specific antibody to destroy the particular microbe that has invaded the body. Red bone marrow continually produces white blood cells, except lymphocytes and monocytes, and keeps a reserve ready in case of need. Lymphocytes and monocytes are produced by lymphatic tissue located in the lymph nodes and spleen. When a parasite or virus invades and begins to colonize, the reserves of white blood cells are released and the manufacturing of large quantities of the appropriate white cells begins. It is this increased production that causes fever.

Because white blood cells are supposedly specific for various illnesses, their count can supposedly assist doctors diagnose patients. However, as has been shown by researchers at Perth, Australia (The Perth Group), white blood cell counts can also be misleading as many conditions cause very similar counts, leading some researchers to question the emphasis currently placed on white blood cell counts in diagnosis.
Research Leucocytes