Leukocytes are white blood cells that are produced in red bone marrow. They are separated into two major groups: granular and agranular (without granules). There are five different types of leukocytes, and each has a specific function. Basophils, eosinophils and neutrophils are granular leukocytes that have visible granules in their cell make-up. Lymphocytes and monocytes are agranular, having no granules making up the cell matrix. Leukocytes function to produce antibodies and fight infection by phagocytosis.
Pronounced fag-oh-sigh-TOH-sis, it is the process of leukocytes engulfing and destroying microorganisms and debris from dead cells. All five leukocytes have phagocytic responsibilities, but only two have the responsibility full time. Monocytes and neutrophils are the active leukocytes for carrying out phagocytosis.
This group includes basophils, eosinophils, and neutrophils. Each have some phagocytosis responsibility but each have a specific function. Basophils release histamine and are involved with hypersensitivity allergies; they increase when a person contracts the chickenpox. Eosinophils increase during allergic reactions like hay fever, and also with parasite infections. Neutrophils are most active in phagocytosis with an immediate response to infections, and they release antibiotics. Neutrophils are the most numerous of all the leukocytes.
The category of agranular leukocytes includes monocytes and lymphocytes, which are active during leukaemia and viral infections. Lymphocytes increase with leukaemia and mononucleosis and produce antibodies. Monocytes also increase with certain leukaemia, as well as with tuberculosis. They are much slower in phagocytic response but act for a longer period of time and in greater numbers. Monocytes are considered the cleanup crew because they work until all debris is cleaned up.
Neutrophils and monocytes perform the main phagocytic functions. Neutrophils are rapid response cells that target bacterial infections. They are the most numerous of all the leukocytes. Monocytes have a slower response but do so in greater numbers to "clean up" damaged cells and debris. Phagocytosis is an important protective process in our bodies. If leukocytes lost their phagocytic ability, we would die.