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Leucocytes, also known as white blood cells (WBCs), are colorless, transparent cells that circulate in the blood and lymph.
- They are an important element of the immune system.
- Neutrophils, eosinophils, basophils, lymphocytes, and monocytes are the different kinds of leucocytes.
- White blood cells (also known as Leucocytes) are derived from hematopoietic stem cells, just like red blood cells (hemocytoblast).
- Granulocytes and monocytes belong to the myeloid series of Leucocytes.
- Whereas lymphocytes and lymphoid dendritic cells belong to the lymphoid series.
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Key Terms: White blood cells, Leucocytes, RBC, Cells, Immune system, Pathogens, Blood cells, Granulocytes, Agranulocytes
What are White Blood Cells (WBCs)
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White blood cells are also known as Leucocytes or leucocytes. Leucocytes are part of the immune system, which is responsible for:
- Fighting and protecting against invading pathogens.
- Progesterone stimulates progesterone production
- They contribute to the human reproductive system by producing a network of blood vessels within the ovary.
The total number of white blood cells in each microliter of blood varies between 4 and 11 thousand on average, and a healthy person produces 80 to 100 billion white blood cells every day.
- White blood cells have a lifetime of between 13 and 20 days.
- They are nucleotide blood cells that are white in color, therefore the name.
- Granulocytes and agranulocytes are the two types of blood cells.
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Types of White Blood Cells
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Types of White Blood Cells have been elaborated below:
- Monocytes: Their lifespan is longer than that of many white blood cells, and they help break down bacteria.
- Lymphocytes: Word origin: Greek leukos – white, and kytos – cell. Related forms: leukocytic (adjective) Antibodies enable them to fight off bacteria, viruses, and other potentially harmful invaders.
- Neutrophils: Bacteria and fungi are digested by neutrophils. White blood cells are the most common type of white blood cells and your first line of defense against infections.
- Basophils: Whenever an infectious agent enters your bloodstream, these small cells seem to sound the alarm. Among the chemicals they secrete are histamines, which are markers of allergic diseases.
- Eosinophils: In addition to attacking and killing parasites and cancer cells, they also help with allergic reactions.
Problems Affecting White Blood Cells
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A low white blood cell count can be caused by a variety of factors.
- This includes situations when something is killing cells faster than the body can replace them.
- Alternatively, when your bone marrow quits producing enough white blood cells to keep you alive.
- When your white blood cell count is low, you are more susceptible to disease or infection, which can quickly escalate into a major health problem.
A blood test can be performed by your healthcare practitioner to determine if your white blood cell count is normal. You may have a white blood cell disorder if your count is abnormally low or high.
A number of diseases and conditions may affect white blood cell levels:
- Weak immune system: As a result of illnesses such as HIV/AIDS or cancer treatment, this occurs frequently. Chemotherapy and radiation treatment can destroy white blood cells and leave you at risk for infection.
- Infection: Having a greater number of white blood cells than normal usually means you are infected. These cells multiply to destroy harmful bacteria or viruses.
- Myelodysplastic syndrome: A condition characterized by abnormal blood cell production. The condition affects both red and white blood cells.
- Cancer of the blood: Some cancers, such as leukemia and lymphoma, can cause the bone marrow to produce abnormal blood cells. Infections and bleeding can be greatly increased as a result.
- Myeloproliferative disorder: In this disorder, immature blood cells are produced excessively under a variety of conditions. Too many or too few white blood cells in the blood can result from an unbalanced blood cell count in the bone marrow.
- Medicines: Many medicines affect the white blood cell count in the body.
High white blood cell levels are also triggered by extreme physical stress such as an injury or emotional stress.
Methods of Classification of Leucocytes
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Different methods of classification of leucocytes are
Granulocytes
Granulocytes are white blood cells that exist in the cytoplasm in the form of granules. They are also known as polymorphonuclear leukocytes since they contain four lobes.
Granulocytes are of three different types:
- Neutrophils
- Eosinophils
- Basophils
Agranulocytes
These are white blood cells that do not have granules. They have just one lobe and are known as mononuclear leukocytes because they only contain one nucleus. They account for approximately 35% of all white blood cells in the body.
Agranulocytes are of three different types:
- Lymphocytes
- Monocytes
- Macrophages
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Things to Remember
- There are two main types of leucocytes: granulocytes and mononuclear leukocytes (agranulocytes).
- Leucocytes emerge from hematopoietic stem cells in the bone marrow.
- Leucocytes help in pathogen recognition, phagocytosis (ingestion of particles), pathogen destruction, inflammation mediation, and antigen presentation.
- Granulocytes include neutrophils, eosinophils, basophils, and mast cells.
- The granules contain enzymes that damage or digest pathogens and release inflammatory mediators into the bloodstream.
- Mononuclear leucocytes consist of lymphocytes, monocytes, macrophages, and dendritic cells.
- They are involved in both innate and adaptive immune system functions.
Sample Questions
Ques. What is the full form of WBC? (1 Mark)
Ans. The full form of WBC is White Blood Cells.
Ques. Write the names of various types of white blood cells (WBCs). (2 Marks)
Ans. The different types of white blood cells are
- Eosinophils
- Basophils
- Neutrophils
- Monocytes
- Lymphocytes (e.g., plasma cells).
Ques. What are White Blood Cells? (2 Marks)
Ans. White blood cells are part of the immune system. They help your body fight off infections and other diseases. When you get sick, your body makes more white blood cells to fight the bacteria, viruses, or other foreign substances causing your illness. This increases your white blood count.
Ques. Why are RBCs called corpuscles and WBCs called White Blood cells? (2 Marks)
Ans. The term corpuscle refers to a living cell, such as a red blood cell.
WBCs are also known as corpuscles. However, because red blood cells contain hemoglobin and WBC do not, distinguishing WBC from red blood cells is difficult.
Ques. Why white blood cells are called soldiers of our body? (2 Marks)
Ans. White blood cells are known as body soldiers because they supply immunity to our bodies. They aid in the prevention of diseases, infections, allergies, and foreign particles. These cells, like a nation's soldiers, keep our bodies secure and healthy.
Ques. What happens when you have a high level of WBCs? (3 Marks)
Ans. An increase in WBCs is known as leucocytosis. It generally occurs in response to infection, bone marrow or immune disorder, leukemia, inflammation, or injury. Respiratory illness also causes an increase in the level of WBCs. There is no typical cause of the increase in WBCs, which is known as an idiopathic hypereosinophilic syndrome. It can lead to serious complications such as liver, lung, heart, and nervous system damage.
Ques. The fluid medium of blood is called? (3 Marks)
Ans. Blood is a connective tissue that consists of a fluid matrix, plasma, and formed elements. Plasma is a straw-colored, viscous fluid comprising around 55% of the blood. Water covers 90-92% of plasma and proteins contribute 6-8% of plasma. Fibrinogen, globulins, and albumins are the major proteins. Fibrinogens are needed for clotting or coagulation of blood.
Globulins primarily are involved in the defense mechanisms of the body and albumins help in osmotic balance. Plasma also contains small amounts of minerals like Na+, Ca++, Mg++, Cl, etc. Glucose, amino acids, lipids, etc., are also present in the plasma as they are always in transit in the body. Factors for coagulation or clotting of blood are also present in the plasma in an inactive form. Plasma without the clotting factors and the plasma proteins is called serum.
Ques. (i) Describe all the barriers of innate immunity.
(ii) When does innate immunity become active? (3 Marks)
Ans. (i) Barriers to innate immunity are as follows
(a) Physical Barriers Such as skin, mucous, coating of the epithelium, and lining of respiratory, gastrointestinal, and urogenital tracts.
(b) Physiological Barriers Such as acid in the stomach, saliva in the mouth, and tears from the eyes.
(c) Cellular Barriers Certain types of leukocytes (WBC) of our body like, Polymorphonuclear leukocytes (PMNL neutrophils), monocytes, natural killer cells, and macrophages.
(d) Cytokine Barriers Proteins called interferons being secreted by Virus-infected cells,
(ii) Innate immunity in an individual becomes active as soon as any foreign material (virus, bacteria, and pathogen) enters the body.
Ques. What is the main function of white blood cells? (5 Marks)
Ans. White blood cells(WBCs) are the body's defense systems. They attack foreign bodies that invade the blood or any part of the body. Foreign bodies like bacteria, viruses, and fungi render them less invasive and even destroy them.
They are cells involved in the “inflammatory” response. This response develops when tissue is damaged or invaded by microbes. Neutrophils specialize in killing bacteria. Eosinophils kill parasites. Monocytes control inflammation by releasing cytokines. Lymphocytes recognize and destroy cells infected by viruses or transplanted foreign cells.
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