Cellular Biology

How a Phagocytic Cell Destroys Microbes



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Phagocytic cells are just one of the many components contributing to the inner workings of the human body. Phagocytes are the white blood cells; they absorb harmful poisons in the form of bacteria and dying or dead cells from within the body into themselves. They also sometimes absorb harmful foreign particles. The name ‘Phagocyte’ comes from the Greek word ‘Phagein’ (To eat) and the ‘–cyte’ suffix known to mean ‘cell’ in the biology field. Without phagocytes humans’ immune systems would be greatly changed and not nearly as effective in fighting off diseases.

Phagocytes wee first recognized by Ilya Ilyich Mechnikov (1845–1916). He found that they were involved in the defense against microbial infections. Carl Friedrich Claus coined the name ‘Phagocyte’ in Vienna when meeting up with Mechnikov. Later, in 1882 he began to study freely moving cells in the larvae of starfish. He believed they were vital to the animals’ immune systems. His research would prove to be invaluable, being the main reason for what was known about phagocytes.

As the word part ‘Phagein’ would imply, the phagocytes literally devour harmful bacteria in order to protect the body. There are actually two different ways phagocytes can destroy their prey. The two types are intracellular and extracellular. These are exactly how they sound; intracellular killing would take place inside the phagocyte while extracellular killing would take place outside the phagocyte.

Within intracellular, taking place inside the phagocyte, there are two subtypes the phagocyte will use to kill the microbe. Oxygen dependent intracellular is the more effective of the two and involves increased oxygen intake by the phagocyte once the microbe is absorbed. This is called a respiratory burst and in turn produces reactive oxygen-containing molecules that are anti-microbial. The second type of intracellular killing is oxygen independent, of which there are four other subtypes. These are not nearly as effective as oxygen dependent and include using electrically charged proteins, a type that uses lysozymes, one that uses lactoferrins, and a fourth type that uses proteases and hydrolytic enzymes.

Extracellular killing involves stimulating macrophages into producing nitric oxide. The nitric oxide is released from the microphage and kills microbes nearby. Activated macrophages secrete tumor necrosis factor, this helps kill cancer cells and cells affected by virus, it’s invaluable to the immune system.

Phagocytes are an interesting and necessary part of the human and other animal bodies. Without these the immune systems could not work in the way they’ve come to and humans would not be able to fight off diseases as they do.

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More about this author: Kaitlyn Shepanski

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