Leukocytes
There are five different types of leukocytes:
(granulocytes)
- Basophils
- Neutrophils
- Eosinophils
(agranulocytes)
They can be divided into two separate groups: granular and agranular. These granules can be found in the cytoplasm of the cell. However, both granulocytes and agranulocytes contain a small portion of azurophilic granules which can also be identified as lysosomes. Each of the five cells have unique distinguishing features that make them easier to identify amongst each other.
Neutrophils
These are the most common type of white blood cell's and granulocytes consisting of approximately 60-70% of leukocytes. Their multilobed nucleus makes it easy to distinguish them from the other leukocytes. This multilobed feature gives them their other name, polymorphonuclear neutrophils. They are part of the granular cells and contain three types of granules: specific granules, azurophilic granules, and tertiary granules. The granules help determine their phagocytic function. They are motile cells which is important for them because they are the cells that first respond to tissue damage. Neutrophils contain receptors on their cell membrane, these receptors aid the cell in recognizing antigens. Once foreign substances are recognized phagocytosis can occur.
http://en.wikipedia.org/wiki/Neutrophil_granulocyte
Eosinophils
Eosinophils average the same size as neutrophils and consist of about 2-4% of leukocytes. They are granulocytes and contain two types of granules: specific and azurophilic granules. They have a bilobed nucleus with heterochromatic adjacent to their nuclear envelope and euchromatin in the nucleus. Eosinophils are created in the bone marrow then travel to connective tissue via peripheral blood.
Basophils
Basophils are also similar in size to neutrophils. They are rarely found because they occupy roughly 0.5% of leukocytes. The lobed nucleus can be hard to find because of the numerous granules in the cell. Basophils also have two types of granules: specific and azurophilic granules. Their function is similar to those of mast cells. Basophils are created in bone marrow then released into peripheral blood where they migrate as a mast cell precursor. It then has the ability to become a mast cell. Basophils secrete mediators of inflammation such as, histamine, heparin, and heparin sulfate along with other mediators.
http://www.cytochemistry.net/microanatomy/blood/more_basophils.htm
Lymphocytes
Most abundant type of agranulocytes and consist of 30% of leukocytes. There are three sizes of lymphocytes: small, medium, and large. The small cells are the most commonly found (90%). There are three functionally different cell types: T cells, B cells, and Natural Killer cells. T cells can be found in the thymus, they are so named T cells because they have T- cell receptors that function as cell- surface recognition proteins. B cells are active in producing antibodies. NK cells, as the name suggests, are involved in killing virus- infected cells and tumor cells.
http://www.pathologystudent.com/?p=2186
Monocytes
Monocytes are phagocytic cells and are the largest type of leukocyte. They maintain about 1-5% of white blood cells. They move from the bone marrow to the bloodstream where they stay for about 3 days before migrating to different sites of the mononuclear phagocytic system. The nucleus of the monocytes is slightly indented and contains centrioles and a developed Golgi apparatus. Monocytes are the second cells that appear at sites of inflammation where they develop into a macrophage.
http://faculty.une.edu/com/abell/histo/histolab3a.htm
Having knowledge about these various kinds of leukocytes and their functions is beneficial. For example, neutrophils use receptors during phagocytosis such as toll -like receptors. Toll- like receptors release a fever- causing agent called pyrogen. Prostaglandins are synthesized and produce a fever by acting on the thermoregulatory center of the hypothalamus located in the brain. Therefore, a fever is the bodies natural defense to pathogens trying to invade.
