In this video, we're going to talk some more details about neutrophils. Recall from our last lesson video that neutrophils are one of the 3 types of granulocytes. These neutrophils are the most abundant type of leukocyte, or the most abundant type of white blood cell in the blood. In fact, they can make up to 70% of all leukocytes in the blood, which is the overwhelming majority. These neutrophils also will be able to migrate to different locations via the bloodstream, and they are able to respond to a site of infection or tissue damage. Usually, they are going to be the first to respond to an infection or tissue damage. So they are going to be the first cells to be recruited to the site of infection or the site of damage.
The granules that these neutrophils contain are going to have a variety of different antimicrobial peptides, including defensins, as well as hydrolytic enzymes that have the ability to degrade microbes and destroy microbes. The granules themselves can also be released into the environment. This process of releasing the granules is referred to as degranulation. These granules can either be released through degranulation, or the neutrophil could destroy the microbes during phagocytosis. Phagocytosis is the process of ingesting and digesting material that has been brought in from the outside, and this includes invading microbes. Phagocytosis is sometimes referred to as cell eating.
Another really interesting thing that these neutrophils can do is they can actually release neutrophil extracellular traps or NETs, which really act as webs of chromatin. They essentially release their own DNA into the environment to serve as a net or a trap that will once again trap infecting microbes in the DNA that they release. Trapping the microbes can be an important defense mechanism, focusing specifically on these neutrophils at the moment.
Notice that these neutrophils, again, they have these 5 lobes, they have these smaller granules that do not stain very well. Here's an image of what a neutrophil could look like under a microscope. Notice that here we're showing you an image of some kind of sharp object penetrating into the skin and penetrating tissue. When a sharp object penetrates into the tissue, it can create an area where microbes, pathogenic bacteria might be able to enter into our tissues. Notice that neutrophils are usually the first cells to respond to the injury and they're the first cells to be recruited to the site of infection or the site of damage.
Notice that these neutrophils, they travel through the bloodstream, and they're able to leave the bloodstream into the site of infection. These neutrophils are geared to fight the pathogenic microbes, to defend us from these pathogenic microbes. They can do this either via phagocytosis, where they can ingest microbes and degrade microbes. They can also, like what this neutrophil is doing, they can degranulate, which recall means they can release their cytoplasmic granules into the environment so that those cytoplasmic granules can act on those microbes and destroy the microbes, and they can also release those NETs or those neutrophil extracellular traps, or NETs that once again serve as webs of chromatin to trap infecting microbes.
Notice here in this image right here, we're showing you a neutrophil that is releasing its net, its web of DNA to trap the microbes. These neutrophils, another thing they can do is they can also recruit other immune cells to fight the infection. Notice that these, wandering macrophages are also being recruited to this area so that they can also help fight off these microbes that have invaded. This here concludes our brief lesson on neutrophils, and we'll be able to apply some of these concepts as we move forward in our course and also learn about the other granulocytes as well, including eosinophils and basophils as we move forward. I'll see you all in our next video.