The White Blood Cells

By Precious Folaranmi

They are referred to as leukocytes and also regarded as soldiers of the body (immune system) responsible for fighting the body against infectious diseases and strange invaders.

Leukocytes are nucleated and make up about 1% of the whole blood volume. The normal leukocyte count is between 4,000 to 11,000 microliter of blood. When there is low amount and high amount of leukocytes they are referred to as LEUKOPENIA and LEUKOCYTOSIS respectively.

Leukocytes are classified into:
Granulocytes
Agranulocytes

Granulocytes
These are white blood cells that contains granules in the cytoplasm and this includes the following;
Neutrophils
Eosinophils
Basophils

Neutrophils
These are the most abundant type of granulocytes and are also referred to as neutrocytes or heterocytes. The average diameter of neutrophil is 12-15µm. They make up about 50% to 70% of all leukocytes and do not live for a long period of time. The nucleus of neutrophils has lobes which are linked by chromatin and disappears in matured neutrophils. Neutrophils can be segmented or banded (hyper-segmentation of neutrophils is abnormal and is suggestive of vitamin B12 deficiency).

Bacteria, harmful strange substances, dead cells are ingested by neutrophils to protect the body, this process is known as phagocytosis and form class of polymorphonuclear cells with basophils and eosinophils. The process by which neutrophils moves to the site of inflammation in an amoeboid manner is known as chemotaxis. The normal count of neutrophil is 7.5×10^9,when there is increased amount of neutrophil, it is called neutrophila which can be as a result of bacterial infection and decreased amount of neutrophils, this condition is known as neutropenia and this occur when the immune system is used faster.

Eosinophils
These are cells of the immune system responsible for fighting multicellular parasites and also some infections.

These cells are acid loving cells and are also called acidophiles or eosinophiles. They make up about 1-3 % of the whole leukocytes and are 12-17 micrometer in size. These cells can be found in the GIT (gastrointestinal tract), ovaries, spleen, uterus, lymph nodes and medulla. When there is increased number of eosinophils it is known as eosinophilia and it indicates the presence of cancerous cells, parasitic infection, allergies or cancer.

Eosinophilia results into inflammation and tissue damage.

Basophils
They are the least type of granulocytes. During immune response, basophils are responsible for inflammatory reactions and they respond in the formation of acute and chronic allergic diseases like dermatitis, asthma, etc. They are about 0.5% to 1% of all leukocytes.

Basophils contains heparin which is an anticoagulant that prevents the clotting of blood faster and histamine, which is a vasodilator. When there is increased amount of basophil in the body due to infection or allergies, the condition is known as basophilia (greater than 200µl).

Agranulocytes
. Lymphocytes
. Monocytes

Lymphocytes
The production of lymphocytes is known as lymphopoiesis.

Lymphocytes are network of cells that plays a major role in protecting and providing immunity for the body.

They fight against foreign substances in the body such as bacteria, cancers and viruses. They can be found in the body as well as in the lymph tissue. The percentage of lymphocyte in the whole immune system cells is between 18%-42%.

There are three major types of lymphocytes and they are B, T and NK lymphocytes (B, T and NK cells). These cells are produced in the stem cell of the bone marrow. B cells are responsible for producing proteins from the immune system known as antibodies to rage war against foreign substances called antigens. From the stem cell, some cells move to the thymus to form T cells. T cells are responsible for fighting cancerous cells and also regulate the response of the immune system towards strange substances. NK cells are known as natural killer cells, they kill cancerous cells or cells that are infected by virus and also respond quickly to strange substances.

When there is increased amount of lymphocytes, this condition is known as lymphocytosis which can be as a result of viral infection, and low amount, lymphocytopenia.

Monocytes
Monocytes are about 2-8% of the white blood cells and they help to fight the body against viruses, bacteria and all other infections in the body. When the amount of monocyte is above the normal range, this condition is known as monocytosis.

This condition can be due to viral infection (measles, mumps, mononucleosis), tuberculosis, parasitic infection and chronic inflammatory disease.