s (RBCs), which carry oxygen and other materials to all tissues of the body; white blood cells (WBCs) that fight infection; and the platelets, which play a part in the clotting of the blood. White blood cells can be further subdivided into three main types: granulocytes, monocytes, and lymphocytes. The granulocytes have particles (granules) inside them, containing special proteins (enzymes) and several other substances that can break down chemicals and destroy microorganisms such as bacteria. Monocytes are the second type of white blood cell and are also important in defending the body against pathogens. The lymphocytes are the third type of white blood cell, of which there are two main types -- T lymphocytes and B lymphocytes --having different functions within the immune system. The B cells protect the body by making "antibodies," or proteins that can attach to the surfaces of bacteria and viruses to send signals to many other cell types to come and destroy the antibody coated organism. The T cells protect the body against viruses by recognizing invading proteins and making certain chemicals that are capable of destroying the virus infected cells. T cells can also destroy some types of cancer cells (Gale Encyclopedia of Medicine, 1999, 1758).
The bone marrow makes stem cells, which are the precursors of the different blood cells, and these mature through stages into either RBCs, WBCs, or platelets. In acute leukemias, the maturation process of the white blood cells is interrupted as the immature cells (or "blasts") proliferate rapidly and begin to accumulate in various organs and tissues, thereby affecting their normal function. This uncontrolled proliferation of the immature cells in the bone marrow affects the production of the normal red blood cells and platelets as well. There are two types of acute leukemia: acute lymphocytic leukemia and acute myelogenous leukemia. Different types of white blood cells are involve...