Difference Between Granular and Agranular Leukocytes

The key difference between granular and agranular leukocytes is that granular leukocytes have granules in their cytoplasm, but agranular leukocytes lack granules in the cytoplasm.

Leukocytes or white blood cells are one of the main types of blood cells. They are spherical in shape and colourless compared to red blood cells. The number of WBCs in blood has a range of 7,000-10,000/mm³. There are five types of WBCs, which can be distinguished by their staining characters, size, and the shape of their nuclei. Based on the staining character, there are two types as granulocytes and agranulocytes.

CONTENTS

1. Overview and Key Difference
2. What are Granular Leukocytes
3. What are Agranular Leukocytes
4. Similarities Between Granular and Agranular Leukocytes
5. Side by Side Comparison – Granular vs Agranular Leukocytes in Tabular Form
6. Summary

What are Granular Leukocytes?

Granular leukocytes are the leukocytes that have granules in their cytoplasm. Granulocytes contain a lobed nucleus. They are all capable of amoeboid movement and are further subdivided into neutrophils, eosinophils and basophils.

Neutrophils are the most abundant white blood cells present in our bloodstream accounting for 55-70% of total white blood cells. These cells are extremely important since they can move freely through the walls of veins and into the tissues of our body and immediately act against all antigens. In fact, neutrophils are one of the first cell types that run immediately to the site of infection. These cells form an essential part of the innate immune system.

Basophil is another type of granular leukocyte. Basophils have granules on their surfaces. These granules are filled with enzymes called histamine and heparin. These enzymes are important in inflammation, allergic reactions and asthma. They are mostly found on the skin and mucosa tissues, which are the lining tissues of openings in the body. Basophils account for 1% of the overall white blood cells in the body.

Eosinophils are the third type of granular leukocytes that help to fight against diseases. The number of eosinophils in our blood increases during a parasitic infection, an allergic reaction or a state of cancer.

What are Agranular Leukocytes?

Agranular leukocytes are the leukocytes that possess a non-granular cytoplasm and either an oval or a bean-shaped nucleus. There are main types of agranulocytes as monocytes and lymphocytes. Agranulocytes help our body to fight against diseases and external infections through phagocytosis and making antibodies.

Monocytes are the largest type of white blood cells that account for 2-10 % of the total white blood cells in the bloodstream. Monocyte has an oval-shaped or bean-shaped nucleus and a non-granulated cytoplasm. Moreover, monocyte can differentiate into macrophages and myeloid lineage dendritic cells. Dendritic cells are antigen-presenting cells, while macrophages are phagocytic cells.

Lymphocytes are the main type of cells found in the lymphatic system. There are three types of lymphocytes as T lymphocytes, B lymphocytes and natural killer cells. Natural killer cells recognize and destroy altered cells or cells that have been infected by viruses. B cells produce antibodies which recognize foreign antigens and neutralize them.

B cells are two types: memory B cells and regulatory B cells. There are two types of T cells. One type of T cells produce cytokines that induce the immune response while the second type produces granules that are responsible for the death of the infected cells. Lymphocytes, mainly T and B cells, produce memory cells which provide long-lasting immunity against specific pathogens.

What are the Similarities Between Granular and Agranular Leukocytes?

• Granualr and agranular leukocytes are immune cells.
• They are nucleated white blood cells produced and derived from multipotent cells in the bone marrow.
• These cells protect us by fighting against infectious particles or antigens which cause diseases.
• They circulate via the circulatory system.
• Hence, they are found in the blood and lymphatic system.

What is the Difference Between Granular and Agranular Leukocytes?

Granular leukocytes contain granules in their cytoplasms while agranular leukocytes lack granules in their cytoplasms. Thus, the presence and absence of granules in the cytoplasm is the key difference between granular and agranular leukocytes. Moreover, there are three main types of granular leukocytes as neutrophils, eosinophils and basophils while there are two main types of agranular leukocytes as monocytes and lymphocytes. So, we can consider this too as a difference between granular and agranular leukocytes.

Summary – Granular vs Agranular Leukocytes

Leukocytes are the main cells of the immune system of our body. They protect us from the invading pathogens that could disrupt normal functioning. There are two main types of leukocytes: granulocytes and agranulocytes. Granular leukocytes contain granules in their cytoplasm while agranular leukocytes lack granules. This is the key difference between granular and agranular leukocytes. Neutrophils, eosinophils and basophils are granular leukocytes while lymphocytes and monocytes are agranular leukocytes.

Reference:

1. “Granulocyte.” Wikipedia, Wikimedia Foundation, 1 Nov. 2019, Available here.
2. OpenStax. “Leukocytes and Platelets .” Anatomy and Physiology, OpenStax, 6 Mar. 2013, Available here.

Image Courtesy:

1. “Figure 40 02 03ab” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “Monocytes 12” By Servier Medical Art (CC BY 2.0) via Flickr