White blood cells (WBC) or leukocytes are vital cells of the immune system protecting the human body against infections, bacteria, microbes, viruses and pathogens. These cells are produced in the stem of the bone marrow and are composed of granulocytes (Neutrophils, eosinophils, and Basophils) and non-granulocytes (lymphocytes and monocytes).
WBC’s are constantly circulating through the blood stream and once they identify a particular antigen, they immediately launch a counterattack. These cells are responsible for providing required immunity, without which it will be impossible for the body to fight against any kind of infections or diseases.
So what exactly is their function?
White blood cells act as the defending army of the human immune system providing a shield against several diseases and viruses. An inherently weak or defective immune system can lead to increased susceptibility to infection, allergies, autoimmune diseases and sometimes even cancer. These cells have a density of about 4 – 11 billion per liter of blood.
White blood cells also help produce antibodies which identify invaders and destroy body cells which have become contaminated with invading microbes. The contaminated cells survive couple of days but when they die, they are destroyed by surrounding white blood cells and replaced with new ones.
White blood cells are asymmetrical, colorless and do not contain hemoglobin.They have the ability to change their shape, which enable them to penetrate into the walls of blood vessels and between other cells. White blood cells divide by a process of mitosis, forming either more stem cells or white blood cells that can differentiate into specific white cell types, such as lymphocytes.
Let’s find out the types of White Blood Cells
Neutrophils, lymphocytes, monocytes, eosinophils and basophils are the major types of white blood cells and each of them carry out unique functions for the immune system. These cells play an important role in the immune system by protecting the body from various organisms and infections that contain diseases.
Neutrophils, eosinophils and basophils are collectively known as granulocytes due to prominent granules in their cytoplasm.
Lymphocytes and monocytes do not contain granules and are therefore classified under non granulocytes.
A brief description of each type of white blood cells:
Neutrophils are the most common types of white blood cell which make up 55-70% of the total white blood cells and shelter the body against disease and infections by removing and destroying bacteria, microbes, viruses, foreign substances, and other cells. These cells play a vital role by absorbing any invading microbes that try to enter the bloodstream.
Eosinophils are produced in the bone marrow and circulate at relatively low levels in the blood stream. About 2 – 5% of total white blood cells are comprised of eosinophils. These cells are normally found outside blood vessels in organs rather than bone marrow. A large number of eosinophils are generally found in the gastrointestinal tract. They protect the body by engulfing and killing bacteria, viruses, pathogens and other microorganisms. Eosinophils can destroy cancer cells and secrete substances which help to stop chemicals that mediate infections and also assist the body by performing phagocytosis.Through the process of diapedesis, eosinophils can directly attack localized infections in the tissue.
Basophils are the rare type of white blood cells which constitute only 1% of the total white blood cells count. They contain dark purple granules in the cytoplasm. They generally secrete biologically active substances such as histamine, proteoglycans, or cyclooxigenase products.
These cells are produced in the stem of the bone marrow. Due to the presence of IgE on their surfaces, they help release chemical mediators that cause allergic symptoms and thus play a vital role in the allergic responses. Basophils generally circulate throughout the body in the blood stream and immediately respond to pathogens, microbes or any other infectious agent with help of other types of white blood cells. Basophils also aid phagocytosis and invoke the process of inflammation when body experiences some kind of pain.