The key difference between monocyte and macrophage is that monocyte is the largest type of white blood cell that can differentiate into macrophages or dendritic cells while macrophage is a large specialized white blood cell that engulfs infectious particles and cleans micro debris.
The immune system has different types of cells including lymphocytes, macrophages, monocytes, neutrophils, and other cells such as basophils, eosinophils, and natural killer cells. Macrophages and monocytes are the large white blood cells with an irregular shape; they stimulate antibody production in the body. Both these cell types are agranulocytes due to the absence of cytoplasmic granules. These two types of cells have similar roles in the immune system such as phagocytosis, presenting antigens to T lymphocytes, and production of cytokine that help to initiate and coordinate immune responses.
CONTENTS
1. Overview and Key Difference
2. What is a Monocyte
3. What is a Macrophage
4. Similarities Between Monocyte and Macrophage
5. Side by Side Comparison – Monocyte vs Macrophage in Tabular Form
6. Summary
What is a Monocyte?
Monocytes are irregular shaped white blood cells that circulate in the bloodstream. Unlike other white blood cells, monocytes are large and have a bean-shaped nucleus in the cell. When monocytes enter an organ or tissue from the bloodstream, they differentiate into cells called ‘macrophages’; thus monocytes are the precursor cells of macrophages.
Figure 01: Monocyte
About 3 – 8% of the white blood cells are monocytes in the human circulatory system. All white blood cells are derived from progenitor cells. However, in this case, progenitor cells are differentiated into monoblast and then into promonocytes. Promonocytes are finally differentiated into monocytes. The three main functions of monocytes are phagocytosis, presenting antigens, and production of cytokines.
What is a Macrophage?
Once monocytes reach an organ or a tissue from the bloodstream, they will differentiate into macrophages. Macrophages are large, irregular shaped, agranulated cells with a large bean-shaped nucleus. They are capable of engulfing foreign particles, which could be a threat to human health or cause diseases to humans. We call this engulfing process phagocytosis. Once they engulf foreign particles, they form a membrane-bounded phagosome surrounding them. Then the lysosomes release their enzymes in order to kill, and digest engulfed particles. In addition, rapidly produced oxygen-containing free radicals in phagosomes also help to degrade the pathogens.
Figure 02: Macrophage
Macrophages are capable of engulfing bacteria, viruses, cellular debris, and dust particles in the lungs. When an infection occurs in a tissue or an organ, monocytes in the bloodstream squeeze through the epithelium cells and enter the site of infection. At the site of infection, the monocytes differentiate into active, phagocytic macrophages.
What are the Similarities Between Monocyte and Macrophage?
- Both monocyte and macrophage are white blood cells as well as immune cells.
- They are agranulocytes.
- Moreover, they are phagocytes.
- They are irregular in shape.
- Both are capable of presenting antigens.
- Furthermore, they produce cytokines.
What is the Difference Between Monocyte and Macrophage?
Monocytes and macrophages are two types of white blood cells. Monocytes are the largest type of white blood cells that have the ability to differentiate into macrophages and dendritic cells. On the other hand, macrophages are specialized cells that involve in innate immunity by engulfing infectious particles. This is the key difference between monocyte and macrophage. Another difference between monocyte and macrophage is their size; a monocyte is larger than a macrophage. Furthermore, monocytes are present in the bloodstream, whereas macrophages are present in the extracellular fluid that bathes tissues. Therefore, this is also a difference between monocyte and macrophage.
Summary – Monocyte vs Macrophage
Monocytes and macrophages are two types of white blood cells in the blood. In fact, monocytes are the precursor cells of macrophages. Monocytes migrate into tissues and differentiate into macrophages. Furthermore, monocytes can differentiate into dendritic cells as well. However, macrophages are specialized cells in innate immunity. They engulf bacteria, viruses, etc. and remove micro debris from our bodies. Macrophages are smaller. Thus, this is the difference between monocyte and macrophage.
Reference:
1. “Monocyte.” NeuroImage, Academic Press, Available here.
2. “Macrophages, Definition, Function, Types”, Study.com, Available here.
Image Courtesy:
1. “Macrophage” By The original uploader was Obli at English Wikipedia. – Transferred from en.wikipedia to Commons (CC BY-SA 2.0) via Commons Wikimedia
2. “Monocytes, a type of white blood cell (Giemsa stained)” By Dr Graham Beards – Own work (CC BY-SA 3.0) via Commons Wikimedia