Preksha Meditation & Human Health: 2.3.2.1 Functions

White blood cells contribute to general function to protect the body from infectious disease and to provide immunity to certain diseases. Each kind of leukocyte makes a contribution to this very important aspect of homeostasis. Neutrophils and monocytes are capable of the phagocytosis of pathogens. Neutrophils are the more abundant phagocytes, but the monocytes are the more efficient phagocytes, because they differentiate into macrophages, which also phagocytize dead or damaged tissue at the site of any injury, helping to make tissue repair possible. During an infection, neutrophils are produced more rapidly, and the immature forms, called band cells, may appear in greater numbers in peripheral circulation (band cells are usually less than 10% of the total neutrophils). The term "band" refers to the nucleus that has not yet become segmented, and may look somewhat like a dumbbell. Eosinophils are believed to detoxify foreign proteins and will phagocytize anything labelled with antibodies. This is especially important in allergic reactions and parasitic infections such as trichinosis (a worm parasite). Basophils contain granules of heparin and histamine. Heparin is an anticoagulant that helps prevent abnormal clotting within blood vessels. There are two major kinds of lymphocytes, T cells and B cells, and a less numerous third kind called natural killer cells. For now we will say that T cells (or T lymphocytes) help recognize foreign antigens and may directly destroy some foreign antigens. B cells (or B lymphocytes) become plasma cells that produce antibodies to foreign antigens. Both T cells and B cells provide memory for immunity. Natural killer cells (NK cells) destroy foreign cells by chemically rupturing their membranes. As mentioned earlier, leukocytes function in tissue fluid as well as in the blood. Many WBCs are capable of self-locomotion (amoeboid movement) and are able to squeeze between the cells of capillary walls and out into tissue spaces (Guyton, 1982).