Granulocytes - Diagram, Types, Function, Development and Disorder

Granulocytes: Granulocytes are the most prevalent type of white blood cell. They have enzyme-filled granules in their cytoplasm, which is a thick, semi-fluid substance inside the cell. When there is an infection or inflammation in the body, granulocytes move quickly to the affected area and release their granules to combat the infection. These cells are also known as granular leukocytes, polymorphonuclear leukocytes, or PMNs. The article below offers detailed NEET Biology Notes on granulocytes, including their types, functions, and other relevant information.

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Granulocytes Types

Types of granulocytes include:

Eosinophils

Basophils

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Granulocytes Function

1. Phagocytosis: Granulocytes can engulf and destroy foreign particles, such as bacteria and fungi. Neutrophils are the most active granulocytes in phagocytosis.
2. Degranulation: Granulocytes contain granules filled with enzymes and other chemicals that can kill pathogens and damage tissues. When a granulocyte encounters a foreign particle, it releases these granules in a process called degranulation. The released chemicals can directly kill pathogens or attract other immune cells to the infection site.
3. Inflammation: Granulocytes release chemicals that promote inflammation, helping to contain infections and isolate damaged tissues. Inflammation is a normal immune response, but it can be harmful if uncontrolled.
4. Antigen Presentation: Granulocytes can present antigens (foreign molecules) to T cells, aiding in the activation of the immune response. T cells, another type of white blood cell, play a central role in the adaptive immune system. When a granulocyte presents an antigen to a T cell, it activates the T cell to attack the pathogen associated with the antigen.

Granulocyte Conditions and Disorders

Causes of High Granulocyte Levels (Granulocytosis)

• Infections: Bacterial infections often trigger the production of more granulocytes to combat the invading bacteria.
• Inflammatory Diseases: Conditions like rheumatoid arthritis and psoriasis can lead to increased granulocyte levels.
• Autoimmune Diseases: Diseases such as lupus and inflammatory bowel disease cause the immune system to attack the body's own tissues, resulting in higher granulocyte counts.
• Blood Cell Cancers: Certain cancers, like chronic myeloid leukemia (CML), can cause the bone marrow to produce excessive granulocytes.
• Other Factors: Smoking, stress, and certain medications can also contribute to granulocytosis.

Causes of Low Granulocyte Levels (Granulocytopenia)

• Bone Marrow Disorders: Disorders like aplastic anemia and leukemia can damage the bone marrow, leading to decreased granulocyte production.
• Infections: Infections such as HIV and viral hepatitis can impair the bone marrow and lower granulocyte levels.
• Chemotherapy: Cancer treatments like chemotherapy can harm the bone marrow, reducing its ability to produce granulocytes.
• Spleen Issues: An enlarged spleen can trap granulocytes, resulting in lower levels in the bloodstream.
• Vitamin Deficiencies: Lack of vitamin B12 and folic acid can diminish granulocyte production.
• Autoimmune Diseases: Conditions such as lupus can target and destroy granulocytes, leading to lower levels.

Granulocytes and Agranulocytes

1. Neutrophils: These are the most abundant and work by engulfing and destroying bacteria and fungi.
2. Eosinophils: They combat parasitic infections and are involved in allergic reactions.
3. Basophils: These participate in inflammatory responses and release substances like histamine and heparin.

1. Lymphocytes:

• B cells: Produce antibodies.
• T cells: Include helper, cytotoxic, and regulatory T cells.
• Natural Killer (NK) cells: Target and destroy virally infected and tumor cells.

2. Monocytes: These are the largest white blood cells; in tissues, they transform into macrophages and dendritic cells. These cells engulf pathogens and present their antigens to T cells.