Leukocytes, or white blood cells, help off infections and other diseases. They help with the immune system, so when the number of white blood cells is reduced, it becomes very serious. There are five types of leukocytes.
Neutrophils, or granulocytes, are white blood cells which attack the infection before other white blood cells. They are the most numerous of all leukocytes. When bacteria are found, neutrophils will surround the bacteria and kill it, often dying in the process.
The monocyte's primary purpose is to help with immune defense and rebuild damaged tissue. They also produce proteins for the body and antigens, which stimulate antibody production.
Eosinophils are white blood cells that protect the body by killing and swallowing up bacteria. If the eosinophil cannot enlarge enough to engulf the bacteria it will attach itself and kill the organism.
Basophils increase their numbers when the body has an infection, accumulating at the site of infection. They discharge serotonins and histamines to help increase blood flow and decrease inflammation.
Lymphocytes are primarily responsible for helping out the body's immune system. They consist of B cells and T cells. B cells release antibodies into the body's fluids while T cells directly attack viruses.