Leukocytes or white blood cells provide the body defense against invaders like bacteria, viruses, fungi and cancer. The cells are made in the bone marrow and occur throughout the body including the blood and lymphatic system which is part of the immune system. Leukocytes differ from each other by the amount of granules present in them and are known as granulocytes--contain granules, and agranulocytes--contain no granules. Granules are tiny structures within the cells that contain chemicals used for fighting off infections.
Granulocytes
Granulocytes are also known as Polymorphonuclear leukocytes which means they have irregular shaped nuclei that is lobe-shaped unlike other cells that have round nuclei. There are three types of granulocytes that vary by the method of stain used to identify them according to the Community College of Baltimore. Neutrophils prove the most abundant form of leukocyte and consist of 54 to 75 percent of all white blood cells; and have a life span of a few hours to few days. These cells ingest bacteria and release chemicals to destroy microbes. They may also release chemicals to destroy surrounding cells if they become infected. Neutrophils can move into tissues by releasing chemicals, which dilate blood vessels making it more permeable. Eosinophils consist of 1 to 4 percent of all white blood cells and have a life span of 8 to 12 days. They primarily defend against protozoa, fungi and parasitic worms. They also release chemicals that aid in inflammation to assist the body during infection. Basophils make up between 0 to 1 percent of the white blood cells and have a life span of a few hours to few days. They prove responsible for releasing chemicals that aid in inflammation and mucus production to wash out microbes from the body.
Agranulocytes, Monocytes
Agranulocytes are also known as Mononuclear leukocytes because of the compact nuclei and no granules, says the Community College of Baltimore County. The two types of agranulocytes include Monocytes and Lymphocytes. Monocytes make up 2 to 8 percent of white blood cells; called Phagocytes, which ingest bacteria, foreign bodies and dying cells. Monocytes live for several months and can divide further into Macrophages and Dendritic cells. Macrophages are located throughout the body and are responsible for ingestion, inflammation and presenting invaders to T-Cells for destruction. Dendritic cells are found in the skin, respiratory tract, digestive system and lymph system. Their function is to present invaders to T-Cells for destruction.
Agranulocytes, Lymphocytes
Lymphocytes make up 25 to 40 percent of white blood cells and have a life span of days to years, says the University of Virginia Department of Biomedical Engineering. They occur in the blood and lymph systems and comprise three groups. B-lymphocytes make up 10 to 20 percent of lymphocytes and produce antibodies to fight-off infection. T-lymphocytes make up 60 to 80 percent of lymphocytes and provide immunity against cells infected by viruses or cancer. Natural Killer cells kill cells that have antibodies attached to them.
