White blood cells or Leucocytes
White blood cells are present in our blood and form the majority of our immune system. Our immune system is heavily dependent on these cells as these are the ones responsible for destroying parasites and other foreign bodies in our blood, thus protecting our body from diseases and infections. White blood cells are also known as Leucocytes among doctors and scientists. There are many types of WBCs in our blood, two of the major types being granulocytes and agranulocytes. These two types of WBCs have their own special role to play in the protection of the human body against harmful intruders. In this article, we are going to do a thorough study of these two types of leucocytes to have a better understanding of the workings of the human immune system.
Granulocytes make up about 70 to 75% of the white blood cells in our body. Granulocytes contain small and visible granules in their cytoplasm, which get replaced every 12 hours. They are further divided into 3 main groups.
- Basophils – Basophils are present in very low quantities in our white blood cells, forming only about 1% of the WBCs. However, despite their low quantities, these are as vital to our immune system as the other categories of granulocytes. Basophils release histamines in our body which help in the natural treatment of infections. Histamines are also responsible for initiating the inflammatory reaction of our body.
- Eosinophils – Eosinophils make up 4% of the WBCs of our body. Their job is to ward off infections and parasites that give rise to allergies. The levels of eosinophils increase tenfold when the body suffers from any kind of allergies. For example, if you get your WBCs tested during hives or allergy induced asthma attacks, you will notice that the eosinophils levels have increased.
- Neutrophils – Neutrophils form majority of the white blood cells or leucocytes in our body. With almost 65% of our WBCs being neutrophils, these protect us from all sorts of fungal and bacterial attacks. Also known as polymorphonuclear leukocytes or PMN, these affect the inflammatory system of the body. Elevated levels of neutrophils mean that the body is under the attack of some bacterial or fungal disease or infection.
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Agranulocytes, as indicated by their names, do not contain any kind of granules in the cytoplasm of their cells. They do not have any membrane covering around the cells either, which is a distinguishing characteristic of granulocytes. They are of mainly 2 types, namely lymphocytes and monocytes.
- Lymphocytes – Making up around 25% of our white blood cells, lymphocytes are the most important type of agranylocytes. There are, in turn, 3 different types of lymphocytes present in our blood, called T cells, B cells and NK cells.
- T cells – The T cells are divided into two major types called the CD4 and CD8. The CD4 T cells’ main function is to coordinate with the other cells to destroy the foreign elements attacking the body. They are the ones which defend the body against outside parasites like germs and bacteria to keep diseases at bay. On the other hand, the CD8 T cells are the main destroyers of the body. Their job is to go ahead and attack and kill any foreign intrusion in the blood and defeat the unknown cells.
- B cells – The B cells have the job of producing antibodies whenever the body is invaded by infectious germs and bacteria. These antibodies destroy the germs and other foreign elements entering the body by clinging to them and then chemically reacting with them to tear them apart completely.
- NK cells – The NK cells, also known as natural killer cells, have the same function as the CD8 cells. They are meant to destroy the enemy cells and keep the body protected from all kinds of foreign intrusion. Unlike CD8 cells, however, the NK cells do not need activation of any sort and can work on their own.
- Monocytes – Monocytes are a kind of agranulocytes which have a larger life span than all other white blood cells. These cells have a special job to take care of, and that is to search our entire body for waste materials and germs which are hidden in our blood stream. They are basically the patrol guards of our body. The monocytes do a thorough search of our blood stream for such foreign elements, and when they find any previously undetected bacteria, fungi or virus, they attach themselves to the foreign element and tear them apart, break them down and consume them wholly, erasing all traces of the elements.
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Sometimes, when they are unable to wholly consume these elements, they leave small bits and traces of these in the blood stream, bringing them to the notice of the T cells. The T cells then study the chemical nature of these foreign elements and make sure that any further intrusion of such elements are prevented at all costs.
Monocytes can be subdivided into a special type of cells called macrophages. These are basically enhanced forms of the same monocytes and share the same function as them as well. When the monocytes leave the normal blood stream of the human body, and enter the tissues, they transform into macrophages and protect the various tissues of the body.