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Phagocytes and Phagocytosis

Have you ever heard of this complex system inside your body? Learn this for starters!

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Tuesday, November 7, 2023

A Brief Overview : Phagocytes & Phagocytosis

 



Introduction

Phagocytes are cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. Their name comes from the Greek phagein, "to eat" or "devour", and "-cyte", the suffix in biology denoting "cell", from the Greek kutos, "hollow vessel". They are essential for fighting infections and for subsequent immunity. Phagocytes are important throughout the animal kingdom and are highly developed within vertebrates. Phagocytic cells of the immune system consist predominantly of macrophages and neutrophils.

These cells represent the major cellular effectors of nonspecific host defense and inflammation. Through their ability to phagocytize foreign substances and release cytotoxic and proinflammatory mediators, neutrophils and macrophages protect the body from a wide array of pathogens and xenobiotics and play a central role in the host response to tissue injury.

However, these phagocytic leukocytes also possess significant cytotoxic potential. Many of the mediators released by phagocytes to protect the host also have the capacity to damage normal tissue. Thus, overproduction or unregulated release of cytotoxic mediators can lead to increased or prolonged injurious tissue reactions. This chapter reviews the physiological and pathophysiological activity of phagocytic cells of the immune system.


History







The Russian zoologist Ilya Ilyich Mechnikov (1845–1916) first recognized that specialized cells were involved in defense against microbial infections. In 1882, he studied motile (freely moving) cells in the larvae of starfishes, believing they were important to the animals' immune defenses.

 To test his idea, he inserted small thorns from a tangerine tree into the larvae. After a few hours he noticed that the motile cells had surrounded the thorns. Mechnikov traveled to Vienna and shared his ideas with Carl Friedrich Claus who suggested the name "phagocyte" (from the Greek words phagein, meaning "to eat or devour", and kutos, meaning "hollow vessel") for the cells that Mechnikov had observed.

A year later, Mechnikov studied a fresh water crustacean called Daphnia, a tiny transparent animal that can be examined directly under a microscope. He discovered that fungal spores that attacked the animal were destroyed by phagocytes. He went on to extend his observations to the white blood cells of mammals and discovered that the bacterium Bacillus anthracis could be engulfed and killed by phagocytes, a process that he called phagocytosis. Mechnikov proposed that phagocytes were a primary defense against invading organisms.

Phagocytosis






Phagocytosis is the process of taking in particles such as bacteria, invasive fungi, parasites, dead host cells, and cellular and foreign debris by a cell. It involves a chain of molecular processes. Phagocytosis occurs after the foreign body, a bacterial cell, for example, has bound to molecules called "receptors" that are on the surface of the phagocyte. The phagocyte then stretches itself around the bacterium and engulfs it. Phagocytosis of bacteria by human neutrophils takes on average nine minutes.

Once inside this phagocyte, the bacterium is trapped in a compartment called a phagosome. Within one minute the phagosome merges with either a lysosome or a granule to form a phagolysosome. The bacterium is then subjected to an overwhelming array of killing mechanisms and is dead a few minutes later. 

Dendritic cells and macrophages are not so fast, and phagocytosis can take many hours in these cells. Macrophages are slow and untidy eaters; they engulf huge quantities of material and frequently release some undigested back into the tissues. This debris serves as a signal to recruit more phagocytes from the blood. Phagocytes have voracious appetites; scientists have even fed macrophages with iron filings and then used a small magnet to separate them from other cells.





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Thursday, October 5, 2023

The Immune System Versus Cancer Cells + Introduction

Hello, my name is Jassen from class 8C, and I am absent number 11. As of current, I am from Catholic High School, Saint Mary 2. In this blog, I will explain how the immune system prevents cancer. I will also explain what cancer is and how cancer negatively impacts the body. Happy reading!


So first, let's start with the basics. Cancer is a cellular organism that experiences damage to its DNA, which causes mutations and individualism. For a cell to become cancerous, three things must happen. First, of course, the DNA must be damaged. But it's not that simple; in cancer corruption, there are opponents who do nothing except monitor cells and repair damaged DNA. If this is also involved in corruption, then the cells become cancerous. However, to be harmful to the body, cancers must reproduce, and they do this by creating new cells with proteins called "oncogenes.", These proteins are very active during growth but die when growth is complete.

Fortunately, our immune system evolved to kill cancer, and our immune system achieves this goal by using two special cells to kill cancer, namely:



- Killer T cells or T cells (cytotoxic T cells)



- Natural Killer Cells (NK Cells)


These two cells have a special task; for T cells, their task is to monitor our entire body and look for prohibited proteins. In the world, there are many proteins that are very dangerous if produced by cells after their growth period. The T cell's job is to find these proteins and kill the cells that produce them. They know the contents of these cells with something called the "MHC Class I System." Basically, MHC Class I is like a small window that provides information to our immune system. However, if the cancer mutates and stops creating that window, will it become invisible? Yes, but our immune system is more complicated than that. This is where NK cells play a role. If T cells look for things that should not be in the cell body, NK cells look for things that should be in the cell. If cells stop making MHC Class I, they are hiding something, and cells that are hiding something should be killed.

That's all I know about the immune system currently; the immune system is very complex. This is only a small fraction of what our body has to offer. If you want to learn more, I'll link you to some websites where you can learn more :

https://my.clevelandclinic.org/health/body/21196-immune-system

https://www.hopkinsmedicine.org/health/conditions-and-diseases/the-immune-system

https://www.ncbi.nlm.nih.gov/books/NBK279396/

https://www.healio.com/hematology-oncology/learn-immuno-oncology/the-immune-system/the-innate-vs-adaptive-immune-response

https://my.clevelandclinic.org/health/body/24898-natural-killer-cells

https://en.wikipedia.org/wiki/T_cell

https://www.britannica.com/science/killer-T-cell

https://my.clevelandclinic.org/health/body/23370-complement-system

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