Difference Between Neutrophils and Macrophages

Main Difference – Neutrophils vs Macrophages

Neutrophils and macrophages are two types of blood cells found in mammals. Both macrophages and neutrophils are involved in the innate immunity by serving as phagocytes, which engulf and destroy pathogens, dead cells, and dell debris. But, they differ in their morphology and function in the body. The main difference between neutrophils and macrophages is that neutrophils are granulocytes which work as phagocytes only in circulation, whereas macrophages are agranulocytes which work as phagocytes inside the tissues.

Key Areas Covered

1. What are Neutrophils
      – Definition, Types, Characteristics
2. What are Macrophages
      – Definition, Types, Characteristics
3. What are the similarities between Neutrophils and Macrophages
      – Common Features
4. What is the difference between Neutrophils and Macrophages
      – Comparison of Key Differences

Key Terms: Agranulocytes, Chemotaxis, Degranulation, Granulocytes, Lysosome, Macrophages, Monocytes, Neutrophils, Neutropenia, Pseudopodia, Phagocytosis, Phagosome, White Blood Cells

What are Neutrophils

Neutrophils are the most abundant white blood cell type in the blood. They contain a granular cytoplasm as well as a nucleus with two to five lobes. A normal adult produces around 100 billion neutrophils daily.  Neutrophils are one of the first cells to migrate into the site of an inflammation, following the cytokine signals produced by the infected cells. This process of migration is called chemotaxis. Neutrophils show an ameboid movement by extending long projections called pseudopodia. They engulf microorganisms, cell debris as well as dead cells by active phagocytosis. The enzymes stored in the granules are involved in the digestion of phagocytized particles. During the metabolism inside the granules, hydrogen peroxide is produced. The phagocytized particles are encased in a vacuole to which the hydrogen peroxide is released and by the action of hydrogen peroxide, particles are destroyed. The depletion of granules is referred to as degranulation. Neutrophil numbers increase due to acute infections. The abnormal lower numbers of neutrophils are referred to as neutropenia. A neutrophil is shown in figure 1.

Figure 1: A Neutrophil

What are Macrophages

Macrophages are a type of white blood cells, which are active in tissues and are capable of phagocytizing microorganisms. The circulating cells called monocytes are capable of migrating into infected tissues and differentiating into macrophages. Both monocytes and macrophages are agranulocytes. Macrophages engulf unwanted particles and form a phagosome. This phagosome is fused with a lysosome containing enzymes to digest the phagocytized particle. Phagocytes can be found in Langerhans cells in the skin, Kupffer cells in the liver, the pigmented epithelium of the eye and the microglia in the brain. Figure 2 below shows a macrophage forming two pseudopodia to engulf particles.

Figure 2: A macrophage

Similarities Between Neutrophils and Macrophages

• Both neutrophils and macrophages originate from the bone marrow.

• Both of them are professional phagocytes, which are involved in the innate immunity by phagocytosis.

• Both detect pathogens and help to initiate inflammation.

• Both serve as antigen presenting cells.

• Both are capable of enhancing inflammation as well as limit or suppress inflammation.

• They promote tissue repair.

• Neither neutrophils nor macrophages are capable of degrading or detoxifying components of animal venom.

Difference Between Neutrophils and Macrophages

Definition

Neutrophils: Neutrophil is a granular leukocyte, comprising of a nucleus with three to five lobes.

Macrophages: Macrophage is a large white blood cell that engulfs foreign particles in the body.

Shape of the Nucleus

Neutrophils: Neutrophils have a multi-lobed nucleus.

Macrophages: Macrophages have a large, rounded shape nucleus.

Granulocytes/Agranulocytes

Neutrophils: Neutrophils are granulocytes.

Macrophages: Macrophages are agranulocytes.

Makeup

Neutrophils: Neutrophils make up 50-70% of circulating white blood cells.

Macrophages: Monocytes make up 2-8% of circulating white blood cells.

Difference in Phenotype

Neutrophils: Neutrophils consist of Ly6G+, and MPO+ receptors on the cell membrane.

Macrophages: Macrophages consist of EMR1+, CD107b+ (Mac-3+), and CD68+ receptors on the cell membrane.    

Site of Maturation

Neutrophils: Neutrophils mature in the bone marrow.

Macrophages: Macrophages mature in tissues.

Mature Cells in Circulation

Neutrophils: Mature neutrophils are found in circulation.

Macrophages: Very few macrophages can be found in circulation.

Mature Cells Recruited into Tissues from Circulation

Neutrophils: During innate and acquired immunity, mature neutrophils migrate from circulation into tissues.

Macrophages: Only immature monocytes migrate from the circulation into tissues.

Normal Residence of Mature Cells in Connective Tissues

Neutrophils: Mature neutrophils do not reside in connective tissues.

Macrophages: Mature macrophages normally reside in connective tissues.

Phenotypically Distinct Sub-Populations in Different Tissues

Neutrophils: No phenotypic variations are observed in neutrophils.

Macrophages: Macrophages comprise of phenotypically varied sub-populations in distinct tissues.

Proliferative Ability of Mature Cells

Neutrophils: Generally mature neutrophils are incapable of proliferating.

Macrophages: M2 macrophages are capable of proliferating in certain circumstances.

Lifespan

Neutrophils: The lifespan of neutrophils is typically several days.

Macrophages: The life span of macrophages is weeks to months.

Role

Neutrophils: Neutrophils are the first to attack bacteria at the site of infection. The action of neutrophils forms pus.

Macrophages: Monocytes from the circulation enter the peripheral tissues, becoming tissue macrophages, which engulf large particles and pathogens.

Conclusion

Neutrophils and macrophages are professional phagocytes found in the body. Both of them are involved in destroying the pathogens and unwanted particles like cell debris and dead cells. Neutrophils originate in bone marrow and mature during circulation. Macrophages are derived from monocytes, which also originate in the bone marrow. Monocytes migrate into tissues and become macrophages. This is the main difference between neutrophils and macrophages.

Reference:

“Neutrophil.” Encyclopædia Britannica. Encyclopædia Britannica, inc., n.d. Web.Available here. 16 June 2017. 
“Macrophages: Definition, Function & Types.” Study.com. N.p., n.d. Web. Available here. 16 June 2017. 
Galli, Stephen J., Niels Borregaard, and Thomas A. Wynn. “Phenotypic and functional plasticity of cells of innate immunity: macrophages, mast cells and neutrophils.” Nature News. Nature Publishing Group, 19 Oct. 2011. Web. Available here. 16 June 2017. 

Image Courtesy:

1. “Blausen 0676 Neutrophil. “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia
2. “Macrophage” By Obli at English Wikipedia – Transferred from en.wikipedia to Commons (CC BY-SA 2.0) via Commons Wikimedia

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