Neutrophils and Microscopy
Procedure, Observations and Discussion
In human beings, neutrophils (neutrophilic
polymorphonuclear leukocytes) are the most abundant white cells given that they
make up about 60 percent of the total leukocytes (white blood cells).
process known as cell signaling, they have been shown to be the first leukocytes
to arrive at the inflammatory sites to defend the body against such
microorganisms as bacteria and fungus.
At the site of infection, neutrophils
typically ingest the pathogen through a process known as phagocytosis and captured
within the phagocytic vacuole. This is then followed by the release of
digestive enzymes in to the vacuole to destroy and thus neutralize the pathogen
or other foreign particles.
While there are more advanced techniques such as Immunofluorescence microscopy that can be used to view neutrophils, these cells can also be viewed using a simpler blood smear technique.
- Using 70 percent alcohol,
clean the finger tip (the middle or ring finger) and prick using the prick
- Using a cotton swab with
alcohol, wipe away the first drop of blood
- Place a drop or two of
blood on to the center of a clean microscope glass slide (prepare two separate
slides for a thick and thin film)
- Using another clean slide
held at a 45 degree angle, spread the blood on one of the slides to create a
- For the second preparation,
use a clean wire loop or laboratory stick to spread the blood drops to a diameter
of about 1.5 cm.
- Allow the slides to dry
completely (air dry)
- Fix the thin slide using
100 percent methanol
* Make sure the slides are completely dry before
- Place the slides in a jar of Giemsa stain for about 50 minutes
- Rinse the slides several times in plain buffer and place them on a standing rack to dry
- View under the microscope without a cover slips (add immersion oil to view under 1000x)
See Also: Cell Staining
When viewed under the compound microscope,
students will easily detect red blood cells given that they will be the most
abundant cells. However, students will also be able to see neutrophils, which
will not only look bigger than the other cells, but also have several lobes (2
to 5 lobes).
When viewed under high magnification, students will notice that
there are very few of this type when compared to the red cells per given field
Discussion - Neutrophils
Whenever pathogens intrude and enter the tissue
of the host, the epithelium, mast cells and resident tissue macrophages are activated
and start releasing chemokines (C5a, interleukin-8) that in turn attract and
Through a series of events, neutrophils travel up the
chemokine gradient towards the infected area by adhering and emigrating through
the vascular endothelium in a process refered to as chemotaxis.
Although they typically destroy pathogens
through phagocytosis, they can also achieve this by using neutrophil extracellular
traps (NETs) outside the cell. NETs are formed out of processed chromatin that
is combined with granular and specific proteins in the cytoplasm. When released
out of the cell, NETs traps the pathogen, which allows neutrophils to control
the spread of the pathogen.
Related: Basophils, Lymphocytes, Monocytes, Eosinophils, Mast Cells
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