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).
Through a 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.
* Make sure the slides are completely dry before staining.
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 of view.
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 activate neutrophils.
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, Macrophages
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