Types of White Blood Cells (WBCs) and Functions

Types of white blood cells and functions are important for understanding the white blood cells’ normal value in the human body and function. White Blood Cells are also known as leucocytes. Types of White Blood Cells (WBCs) are Neutrophils, Basophils, eosinophils, monocytes, and lymphocytes. White blood cell lifespan is relatively short but plays a vital role in defending the body against infections and maintaining immune function.

Further granulocytes are grouped as neutrophils, basophils, and eosinophils whereas agranulocytes are grouped into monocytes and lymphocytes. Together these cells play a crucial role in the immune system and are hence sometimes called the soldiers of the body. In this article, we will read Types of White Blood Cells (WBCs) and Functions in detail.

What are White Blood Cells?

They are amoeboid, nucleated, and non-pigmented cellular components of the blood or lymph. White blood cells are also known as leucocytes and are slightly larger than the red blood cells. Their size ranges between 8-15 µm. There are 5 types of white blood cells found in the human body. They are neutrophils, basophils, eosinophils, monocytes, and leukocytes. White Blood Cells (WBCs) are mostly formed in the bone marrow and play a crucial role in the body’s defence mechanism.

A healthy human has an average of 7000 leucocytes per cubic milliliter of blood. If the count rises above 20,000 per cubic milliliter, the white blood cell increases causes leukocytosis whereas if the count falls below 4000 per cubic millilitre, the condition is termed as leucopenia.

White Blood Cell Diagram

The diagm of all white blood cell (WBCs) are shown below:

Types of White Blood Cells

White blood cells classification are based on two broad categories depending on the presence of cytoplasmic granules. These categories are granulocytes and agranulocytes.

Granulocytes

Granulocytes are characterised by granular cytoplasm and lobed nucleus. These are produced in the red bone marrow and form around 65% of the total white blood cells in the body. Granulocytes are further classified into neutrophils, basophils, and eosinophils based on the shape of their nuclei and the type of stain they take.

1: Neutrophils

Neutrophils are the chief phagocytic cells and most abundant type of leucocytes in the body. Some typical identifying characteristics of neutrophils are as follows:

• The cell size varies from 10-12 µm.
• The nucleus is 3-5 lobed.
• Cytoplasm contains fine granules that stains with both acid and basic dyes.
• Their life span is typically 10-12 hours.
• They exhibit chemotaxis and move to infected site by following chemical signals.
• They have specialized receptors on their cell surfaces that recognize and bind to pathogens.
• Neutrophils in females have a barr body while in males barr bodies are absent.

Function: Neutrophils play a role in modulating inflammatory responses by releasing cytokines and other signaling molecules that influence the activity of other immune cells and promote tissue repair.

2: Basophils

Basophils make up a small proportion of the total white blood cell count, typically accounting for less than 1% of circulating white blood cells. Identifying characteristics of basophils are as follows:

1. Their size varies from 8-10 µm.
2. The nucleus is bilobed or trilobed and appears S-shaped.
3. Cytoplasmic granules are coarse and get stained with basic dyes like methylene blue.
4. Life span varies from 8-12 hours.
5. They release substances like heparin, serotonin, and histamine.

Function: Basophils play important roles in allergic reactions, parasitic infections, and the regulation of immune responses.

3: Eosinophils

Eosinophils are also known as acidophils. They comprise around 2-3% of the total leucocyte count in the body. Some identifying characters of eosinophils are listed below.

1. Size ranges between 10-15 µm.
2. The nucleus is bilobed.
3. Cytoplasmic granules are coarse and take acidic stains like eosin.
4. Average life span is 14 hours.
5. These are non phagocytic in nature.

Function: Eosinophil release toxic proteins to combat parasitic infections and also contribute to the inflammatory response seen in allergies.

Agranulocytes

Agranulocytes do not have a granular cytoplasm and make up about 35% of the total number of white blood cells present in the body. Depending on their structure, they are further divided into two subtypes: monocytes and lymphocytes.

1: Lymphocytes

Lymphocytes constitute 20-30% of the total leucocyte count in the body. Their main function is to produce antibodies and opsonin. Defining characteristics of lymphocytes are as follows:

1. Their size ranges between 10 -12 µm.
2. The nucleus is large and rounded.
3. Cytoplasm is confined to the periphery.
4. They are formed in the thymus and lymphoid tissues like lymph nodes, spleen, etc.
5. Lymphoblasts are the precursors of lymphocytes.

Functions: Lymphocytes are crucial for adaptive immunity. They establish immunological memory, enabling quicker and more robust responses upon reexposure to pathogens

Lymphocytes are further classified into T-lymphocytes, B-lymphocytes , and Natural Killer Cells.

1. T-Cells: T cells are primarily involved in cell-mediated immunity and play a central role in the adaptive immune response.They mature in the thymus gland and are characterized by the presence of T cell receptors (TCRs) on their surface. T cells are broadly categorized into several subsets, including helper T cells (CD4⁺), cytotoxic T cells (CD8⁺), regulatory T cells (Tregs), and memory T cells.
2. B-Cells: B cells are primarily involved in humoral immunity, which is mediated by antibodies. They originate and mature in the bone marrow and are characterized by the presence of B cell receptors (BCRs) i.e. membrane bound antibodies on their surface. When activated by encountering specific antigens, B cells differentiate into plasma cells, which produce and secrete antibodies.
3. Natural Killer Cells (NK cells) : NK cells play a role in the innate immune system’s defense against infected or abnormal cells, including cancer cells. Unlike T cells and B cells, NK cells do not require prior sensitization or activation by specific antigens to function. NK cells identify and kill target cells by recognizing markers of stress or abnormality on their surface, such as downregulated major histocompatibility complex (MHC) molecules or the presence of certain activating ligands.

2: Monocytes

Monocytes are the largest leucocytes. They form about 5.3% of the total white blood cells in the body. Some identifying characters of monocytes are listed below:

1. Size of monocytes can be upto 20 µm.
2. The nucleus can be oval, kidney shaped, or horse shoe shaped.
3. The nucleus is usually excentric.
4. They are formed in the spleen or lymph nodes.
5. Monoblasts are precursors of monocytes.

Function: Monocytes are highly motile and engulf bacteria. They generally serve in second line of defence. Further they can differentiate into macrophages or scavenger cells.

• Macrophages: Macrophages are found in various tissues throughout the body and are key players in the innate immune system. They engulf and digest pathogens, dead cells, and cellular debris. They also present antigens to activate other immune cells.
• Dendritic Cell: Dendritic cells are specialized antigen-presenting cells found in tissues exposed to the external environment, such as the skin and mucosal surfaces, as well as in lymphoid organs. They play a crucial role in initiating adaptive immune responses by capturing, processing, and presenting antigens to T cells. Dendritic cells are characterized by their dendritic morphology, with numerous cellular extensions that increase their surface area for antigen capture.

Functions of White Blood Cells

White blood cells (WBCs), are essential components of the immune system, responsible for protecting the body against infections, foreign substances, and abnormal cells. The functions of white blood cells include:

• Immune Defense: The primary role of white blood cells is to defend the body against infections caused by bacteria, viruses, fungi, and other microorganisms. They recognize and eliminate these invaders to prevent the spread of infections.
• Phagocytosis: Many white blood cells, such as neutrophils and monocytes, are capable of phagocytosis i.e., they can engulf and digest foreign particles, microorganisms, and cellular debris. This process helps eliminate pathogens and promotes tissue repair.
• Production of Antibodies: Lymphocytes play a important role in adaptive immunity. B cells produce antibodies (immunoglobulins) that specifically target and neutralize pathogens. This antibody-mediated response is essential for long-term immunity.
• Cell-Mediated Immunity: T lymphocytes (T cells) are involved in cell-mediated immunity. They recognize and destroy infected or abnormal cells directly and contribute to the body’s defense against viruses, certain types of cancer, and intracellular pathogens.
• Inflammatory Response: White blood cells release various chemicals, such as cytokines, histamine, and other inflammatory mediators, to initiate and regulate the inflammatory response.
• Early detection and elimination of infections: White blood cells constantly flow around the blood stream and tissues, monitoring for signs of infection, abnormal cells, or other threats. This helps them to detect and respond to potential dangers early on.
• Tissue Repair and Healing: White blood cells contribute to the process of tissue repair and healing by removing debris and promoting the regeneration of damaged tissues.
• Antiparasitic Activity: Eosinophils are specialized in fighting parasitic infections. They release toxic substances that are effective against parasites.

Conclusion – White Blood Cells (WBCs)

White Blood cells are also known as leucocytes. They are soldiers of the body and help the immune system to keep our body healthy. The normal white blood cells count of a human is about 7000 WBCs per cubic millilitres of blood. There are five types of white blood cells found in human body. They are neutrophil, basophil, acidophil, monocytes, and lymphocytes. These 5 cells are grouped into two broad categories, granulocytes and agranulocytes, based on the presence or absence of granules in their cytoplasm. Typically, white blood cells are amoeboid and have a nucleus that distinguishes them from platelets and RBCs. It is important to study about the types of white blood cell and function for better understanding of the immune system.

FAQs on White Blood Cells (WBCs)

What is the Normal Range of WBC?

The normal range of WBC count for a healthy adult is 4500 per cubic milliliter to 11000 per cubic milliliter of blood.

What is the Difference Between a Lymphocyte and a Leukocyte?

Lymphocytes are type of white blood cells that have a large oval nucleus and minimum cytoplasm. Leukocyte is other name give to white blood cell. So we can say lymphocytes are a type of leukocyte.

What is the Function of Neutrophils?

Neutrophils are responsible for innate immunity. They engulf and digest foreign bodies and pathogens. They also secrete substances that trigger the functioning of other immune cells in the body.

What are the 5 Types of White Blood Cells?

The five types of white blood cells are: neutrophils, basophils, acidophils, monocytes, and lymphocytes.

What is a Dangerous White Blood Cell Count?

A white blood cell (WBC) count above 11,000/μL and below 500/μL in adults is generally considered to be fatal.

What is the Function of WBCs?

White blood cells (WBCs) play a crucial role in the immune system, defending the body against pathogens by phagocytosis, producing antibodies, releasing cytokines, and coordinating immune responses.

What is the White Blood Cells Lifespan?

Average life span of a WBC is 8 to 14 hours.

What are White Blood Cells also Known as ?

Another name of WBC is Leukocyte.

Which is the Smallest WBC?

T-Lymphocytes are the smallest White Blood Cells (WBCs).

What is Leucocytes?

Leucocytes, also known as white blood cells, are a vital component of the immune system responsible for defending the body against infections and foreign invaders.