What is the difference between Granulocytes and Agranulocytes?
The first line of defense for our human body against diseases, foreign material, or bacteria is the white blood cells. The white blood cells, also known as leukocytes, are the cells of the immune system which protect our bodies. The presence of white blood cells can be found throughout the blood and the lymphatic system. The white blood cells count in the body gives an indication of the presence of diseases in the body.
The leukocytes can largely be divided into various categories. Based on the structure, they are divided into granulocytes and agranulocytes. Based on the cell lineage, they can be classified into two categories, - lymphoid cells and myeloid cells. The further categorization of the white blood cells can be done on functional and structural characteristics. Based on this the various types of white blood cells that are present in the body are eosinophils, neutrophils, lymphocytes, monocytes, and basophils.
The granulocytes are present within the cytoplasm in the form of granules while agranulocytes exist without the granules. The granulocytes have 4 lobes and agranulocytes are single lobes. We will have a brief discussion of some of these differences between granulocytes and agranulocytes.
Granulocytes and Agranulocytes
The white blood cells are the soldiers of the body which work against any foreign invaders or disease carriers. Depending on the differences in structure, these white blood cells are categorized into granulocytes and agranulocytes. All of the white blood cells have a nucleus present within them unlike the platelets and the red blood cells. We will have a brief look at granulocytes and agranulocytes before documenting the differences between them.
Granulocytes have a specific amount of granules that are present in the cytoplasm. The nucleus which is present in the granulocytes is lobed in three segments. The most abundant granulocytes are the neutrophils. The other granulocytes are basophils, mast cells, and eosinophils. These granulocytes are present in the innate immune system.
Agranulocytes are white blood cells with no granules in their cytoplasm. They have one lobe present within the nucleus. The monocytes and lymphocytes are the agranulocytes that are present within the human body.
Difference between Granulocytes and Agranulocytes
The granules are present in the cytoplasm of granulocytes and these granules are absent in agranulocytes. Granulocytes from 65% of the white blood cells and agranulocytes make up the rest 35% of the white blood cells. The granulocytes originate from the bone marrow while agranulocytes originate from the lymph nodes. The granulocytes are also known as polymorphonuclear leukocytes while agranulocytes are known as mononuclear leukocytes. The granulocytes have various lobes in the nucleus and agranulocytes only have one lobe in the nucleus.
FAQs on Difference Between Granulocytes and Agranulocytes
1. What is the main difference between granulocytes and agranulocytes?
The main difference lies in their cytoplasmic appearance. Granulocytes contain large, visible granules, which are sacs filled with enzymes and other chemicals used to destroy pathogens. In contrast, agranulocytes lack these prominent granules, giving their cytoplasm a clear or 'agranular' look under a microscope. This structural difference is directly related to their specific functions in the immune system.
2. What are the different types of granulocytes and agranulocytes?
These two main classes of white blood cells are further divided into specific types, each with a unique role:
- Granulocytes include:
- Neutrophils: The most abundant type, acting as the first responders to bacterial infections through phagocytosis.
- Eosinophils: Specialised in fighting parasitic infections and are involved in allergic reactions.
- Basophils: The least common type, releasing histamine and heparin during inflammatory responses.
- Agranulocytes include:
- Lymphocytes: Central to the adaptive immune system, including B-cells (produce antibodies) and T-cells (kill infected cells).
- Monocytes: The largest white blood cells that mature into macrophages in tissues, where they engulf pathogens and cellular debris.
3. Why are granulocytes named so, and what is the function of their granules?
Granulocytes get their name from the prominent, stainable granules visible in their cytoplasm. These are not simple storage sacs; they are specialised lysosomes packed with powerful chemicals. Depending on the cell type, these granules contain enzymes like lysozyme and proteases, as well as defensive proteins. When a granulocyte encounters a threat, it releases the contents of these granules to directly destroy the pathogen or signal other immune cells to the site of infection.
4. What are the primary functions of granulocytes and agranulocytes in the immune system?
While both are crucial for immunity, their roles are distinct. Granulocytes are key players in the innate immune response, providing a rapid, non-specific attack. Neutrophils, for example, immediately target and engulf bacteria. Agranulocytes are central to the more complex adaptive immune response. Lymphocytes create highly specific antibodies and form an immunological memory, while monocytes (as macrophages) are vital for cleaning up debris and presenting antigens to lymphocytes to initiate this targeted response.
5. How do lymphocytes, an agranulocyte, differ from neutrophils, a granulocyte?
The key difference is in their mode of action. A neutrophil is a phagocyte that provides a general, immediate response by engulfing and digesting bacteria. A lymphocyte, on the other hand, orchestrates a highly specific attack. B-lymphocytes produce targeted antibodies that neutralise specific pathogens, while T-lymphocytes can directly kill virus-infected cells or regulate the overall immune response. Structurally, neutrophils have a multi-lobed nucleus, whereas lymphocytes typically have a large, single, round nucleus.
6. What is the normal percentage of different types of WBCs in human blood?
In a healthy adult's differential blood count, the approximate percentages of each white blood cell type are as follows:
- Neutrophils: 50-70%
- Lymphocytes: 20-40%
- Monocytes: 2-8%
- Eosinophils: 1-4%
- Basophils: 0.5-1%
A significant deviation from these values often indicates an underlying infection, allergy, or disease.
7. How can a differential blood count help distinguish between a bacterial and viral infection?
A differential blood count is a powerful diagnostic tool that reveals the relative percentage of each WBC type. A sharp increase in the number of neutrophils (a condition called neutrophilia) is a classic sign of an acute bacterial infection. In contrast, an increase in the number of lymphocytes (lymphocytosis) typically points towards a viral infection, as these cells are the primary fighters of viruses.
8. What is the relationship between monocytes and macrophages?
Monocytes and macrophages are essentially two stages of the same cell. A monocyte is an agranulocyte that circulates in the bloodstream. After a short period, it migrates into body tissues, where it undergoes a transformation, enlarging and differentiating into a highly effective phagocytic cell called a macrophage. As a macrophage, it plays a long-term role in that tissue, engulfing pathogens and cellular waste.
9. Why are agranulocytes considered 'agranular' if they also contain lysosomes?
The term 'agranular' is based on historical observations using a standard light microscope. While agranulocytes do contain essential organelles like lysosomes (a type of granule), these are non-specific and too small to be easily seen with standard laboratory staining. Granulocytes, however, possess large, specific granules that readily pick up stains and are clearly visible. Therefore, the classification is based on this visible difference, not the absolute absence of any granular structures.
