White Blood Cells

White blood cells, also known as leukocytes are the blood cells that are considered as an integral part of the immune system. These blood cells are concerned with protecting the body from the foreign infectious agents like, bacteria and virus. They are produced by the cells of the bone marrow. The normal white blood cell count in a healthy adult should be between 4,000 to 10,000 per microliter of blood. There are basically five types of leukocytes. Here is a brief discussion about these various types of WBCs and their functions.

Types of Leukocytes and Their Functions

There are basically five types of white blood cells, which are known as neutrophils, basophils, eosinophils, monocytes and lymphocytes. These five types of WBCs are classified into two categories, granulocytes and agranulocytes. Granulocytes are the leukocytes with granules in their cytoplasm, while agranulocytes are characterized by the absence of such granules in the cytoplasm.

Neutrophils
Neutrophils are the leukocytes of about 10 to 12 micrometer in diameter with multilobed nucleus, for which they are also called polymorphonuclear leukocytes. Neutrophils are characterized by the presence of granules in the cytoplasm, and they are mainly concerned with protecting the body from bacterial and fungal infections. Neutrophils kill the bacteria by directly ingesting them, which is known as phagocytosis. These can be found in large amounts in pus of wounds. Neutrophils account for almost 60 to 70% of total leukocyte count, and their lifespan is about 6 hours to a few days.

Eosinophils
Eosinophils are mainly known for their role in allergic reactions. They have bi-lobed nucleus and their diameter is usually 10 to 12 micrometer. An increase in the number of eosinophils is usually associated with allergies, asthma and hay fever. Eosinophils are also responsible for fighting parasitic infections and hence, parasitic infections can also cause the number of eosinophils to increase in blood. The average life span of eosinophils is 8 to 12 days.

Basophils
Basophils are another type of granulocyte, which are mainly associated with allergic reactions. These cells have a bi or tri-lobed nucleus, and large and coarse granules of blue color in their cytoplasm. They release the chemical histamine during an allergic reaction, which produces the typical signs of allergies such as, itching and hives. The diameter of basophils can be about 12 to 15 micrometer.

Monocytes
Monocytes are agranulocytes and are concerned with phagocytosis like neutrophils. However, they have a much longer life than neutrophils. Monocytes can leave the bloodstream and enter the body tissue, where they undergo some changes and turn into macrophages. As tissue macrophages, monocytes destroy and remove dead, old and damaged cells from the body. An interesting finding about monocytes is that they can replace their lysosomal content. Monocytes possess kidney shaped nucleus and their diameter is usually 14 to 17 micrometer. Monocytes present the fragments of a pathogen to T lymphocytes, so that the T lymphocytes can recognize the pathogen in future. Monocytes remain in the bloodstream for 10 to 20 hours, after which they enter the tissues and live there for several days.

Lymphocytes
Lymphocytes are the leukocytes, which differ from the other white blood cells by the fact that they can recognize the invading pathogens. There are several types of lymphocytes such as, B lymphocytes, helper T cells, cytotoxic T cells, memory T cells and suppressor T cells. B lymphocytes are concerned with antibody production, helper T cells activate and direct the immune system against the invading microorganisms and cytotoxic T cells release chemicals to destroy the pathogens. Memory T cells on the other hand, help the immune system to recognize the particular pathogen, if it is encountered again. Suppressor T cells suppress the immune response when it is no longer required, in order to protect the normal cells of the body.

High Leukocytes

The normal white blood cell count is 4,000 to 10,000 cells per microliter of blood. If the number of leukocytes increases in the body over the upper limit, then the condition is referred as leukocytosis, which usually indicates the presence of an infection in the body. Their elevated count in the body can also be associated with diseases of the bone marrow, drug reaction and a disorder of the immune system.

Low Leukocytes

Leukopenia is the term used for a low leukocyte count. Leukopenia can be caused by several factors, out of which viral infections are worth mentioning. Viral infections can disturb the functions of the bone marrow temporarily to cause leukopenia. Infections, intake of certain drugs, diseases of the liver or spleen and the destruction of the bone marrow caused by certain types of cancer are some other possible low white blood count causes. However, it is possible to increase white blood cell count with a proper diet and a healthy lifestyle, if it is not caused by any serious health problem.

Sometimes, leukocytes can be found in urine and stool as well, which can serve as an indicator of certain illnesses. Presence of high levels of leukocytes in urine can be a sign of infection, especially infection of the urinary tract, bladder and the kidneys. On the other hand, their presence in stool can be caused by conditions like, diarrhea and infection of the intestinal tract.