leukocytes Neutrophil vs. monocyte

Here’s an example of a common question students have in the beginning of a medical school or dental school pathology course. Unfortunately, students often feel like they “should” know the answers to certain questions – so they don’t ask. Don’t fall into this trap! You never need to feel embarassed about asking a question; everyone has things they don’t know – even professors. That’s why you’re taking the class – to learn!

On to the question.

Q. What is the main difference between a neutrophil and a monocyte? This is what I understand:

PMNs:
fight bacteria and fungi (but they are different than NK cells–right?)
act as antigen presenting cells
phagocytic
are generally the first to arrive; part of the acute inflammatory response

Monocytes:
act as antigen presenting cells
can secrete cytokines and attract inflammatory cells like fibroblasts, etc.
phagocytic
bigger role in chronic inflammation

A. Broadly, the similarities are: neutrophils and monocytes are both phagocytes, and they both work to fight infections. But moncytes can turn into macrophages (when they get into tissues), which are very good at eating things, as well as presenting antigens. Neutrophils eat, but don’t present, antigens. One of the big differences, too, you already mentioned: neutrophils are the first to come in during an inflammatory process. Lymphocytes come next, then monocytes/macrophages come in to mop up the mess.

One note: neutrophils are phagocytes, but not antigen presenting cells. Another note: You are right, neutrophils are different than NK cells. NK (natural killer) cells are specialized lymphocytes which have functions different than those of neutrophils and monocytes.

Also: neutrophils look different than monocytes/macrophages. Neutrophils have a “busy” nucleus (that’s why they are called “polymorphonuclear” leukocytes), with several lobes. You can see one at 2 o’clock in the above photo. They also have granules, both primary (azurophilic) and secondary (fawn-colored). Monocytes have a horseshoe-shaped nucleus, with dishwater-gray cytoplasm and a few tiny granules. See the lower left corner in the above photo.

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11 Responses to Neutrophil vs. monocyte

  1. PINKY says:

    I LIKE IT AND I THINK EVERYONE CAN UNDERSTAND IT VERY EASILY IF SHE OR HE HAS A LITTLE BIT OF CONCEPT ABOUT THAT .
    THANKS ALOT…………

  2. Ailinh says:

    So simple thanks to you.

  3. Rivka says:

    I googled “neutrophils and monocytes” after performing a pleural fluid cell count with differential of 53 neutrophils, 17 lymphocytes, 29 monocytes (and 1 mesothelial cell). I was trying to find the connection between the elevated monocytes and neutrophil dominance. Thanks for the helpful information.

  4. Mohini says:

    The problem at times is with premature neutrophils and monocytes.

  5. Kristine says:

    Yes – that can be tough. Probably the toughest would be monocyte vs. myelocyte/metamyelocyte. Promyelocytes are pretty unique looking, with the big granules and blue cytoplasm, and bands look enough like neutrophils that they shouldn’t be a problem. To differentiate monocytes from myelocytes/metamyelocytes, I’d look at:
    1. The chromatin pattern (“raked” in monocytes, already a bit condensed in myelocytes/metamyelocytes)
    2. The cytoplasm (dishwater-like in monocytes, specific granulation (pink) in myelocytes/metamyelocytes)

  6. Mohini Dave says:

    Yes that is true .And in addition when the patient is having viral fever, we get a variety of lymphocytes or what we were taught as monocytoid lymphocytes. The cell counter seems to call most of the band cells and metamyelocytes as monocytes.

  7. Mindi says:

    Would you identify all of the cells in this slide in the following way? Would you say that both the upper and lower left cells are monocytes? That the next cell to the right is a lymphocyte? Is the bilobed cell and eosinophil? Is the tri lobed nucleus the neutrophil? Is the bottom right a basophil?

  8. Kristine says:

    You are almost entirely correct! The only cell I would name differently is the cell at the upper left, which I would call a metamyelocyte. The quality of the chromatin gives it away: it’s clumpy, almost blocky. Monocyte chromatin is smoother and has a “raked” appearance. The cell at the lower left is a monocyte, and the next one over (at 8 o’clock) is a lymphocyte. The bilobed cell is an eosinophil (you can tell by the big, luminous, orangey granules), the cell at the bottom right is a basophil (tons of dark blue-purple granules), and the cell with the nucleus with three lobes or segments is a neutrophil. If you look at that neutrophil and compare it to the metamyelocyte at the top left, you can see that the chromatin is very similar. Also, the cytoplasmic granules are really similar too, with a little more of a pinkish hue to the granules in the segmented neutrophil. Nice job!

  9. Carolyn says:

    this article states that PMN’s and monocytes are antigen presenting. Since PMN’s are neutrophils aren’t they, by definition, NOT antigen presenting? I’m confused because this is what it says later in the article.

  10. Kristine says:

    Thanks Carolyn. Actually, it’s the question from the student (at the beginning of the post) that lists “antigen-presenting” as one of the qualities of neutrophils – but you’re right: as stated later (in my answer), neutrophils are NOT antigen-presenting.

  11. Clovis Palmer says:

    Do anyone have an unpublished microscope image showing monocytes, T cells and neutrophils in the same field? I need it for publication purposes. You will be acknowledged. Thank you

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