Chicken, dog and starfish

At the end of the 16th century, Fabrizius worked at the University of Padua in Italy. He was very interested in the body structure of animals and liked to study anatomy and observe. Once, when he dissected a chicken at home, he found that there was something similar to a purse at the top of the chicken’s body, and he called it a sac. Since then, this sac has been called the “bursa of Fabricius”. However, he did not know that lymphocytes in the immune system are hidden in this sac and can resist foreign diseases.

Decades have passed quietly, and the Italian scientist Gaspare Acelli, like Fabrizius, is also very interested in the body structure of animals. He found a strange milky white vein in the dog’s stomach. This discovery not only surprised Aseli, but also surprised other scholars.

In fact, this milky vein is the lymphatic system in the immune system. The fluid inside is called lymph fluid, which is found in every animal. A part of the lymph fluid in humans and animals enters the venous system and circulates with the blood to absorb protein and act as a transport driver for fat and other nutrients.

In 1882, turmoil broke out in Russia. Zoologist Mechnikov and his family went to live in Sicily, Italy, with a microscope. On the island, Mechnikov’s observation range continued to expand, and he used it for observation as long as it could be collected on land and aquatic.

One day, Mechnikov’s family went to the circus, and he took out a microscope to observe the starfish larvae. Since the starfish larvae are transparent, the cells on them quickly attracted Mechnikov’s attention. It turns out that these cells are not fixed in a certain place, but flow in the starfish without fatigue, just like smart and capable soldiers patrolling the streets. He gave these cells a name-wandering cells. At this moment, he had a whim to see if these cells could drive away invading outsiders like soldiers.

That night, Mechnikov gently pierced a small thorn into the skin of the starfish larva. The next day, Mechnikov found under the microscope that a group of wandering cells were gathering around the thorns, phagocytosing invading tissue cells. This discovery shocked Mechnikov and made him ecstatic.

In fact, the migratory cells discovered by Mechnikov are the phagocytes in the immune system. These cells are produced by the bone marrow of the body. Although the life span is only two or three days, the yield is very high. Some studies believe that the bone marrow can produce 107 phagocytes per minute on average. There are two kinds of cells of this kind, mainly phagocytosis and kill foreign pathogen cells, because they contain lysosomes, which can kill and degrade pathogens. For indigestible bacterial residues, phagocytes can also excrete them outside the cell, which is a protective umbrella for humans and animals.

In most cases, foreign pathogens will be killed by phagocytes. If they are not killed, they will pass through the lymphatic vessels to the nearby lymph nodes, and the phagocytes in the lymph nodes will lift their sharp weapons and kill them. However, there are some very toxic and numerous pathogens that can break through the blockage of phagocytes, clamoring to run into the blood vessels, and then to the liver, spleen and other organs. These very toxic cells are numerous and can be It grows and reproduces inside, which eventually causes disease. Therefore, you should seek medical treatment promptly after you are sick, and use drugs to help phagocytes kill foreign bacteria.

Here, the discovery of the immune system also thanks to a biologist named Paul Ehrlich, who is honored as the “father of immunology.” He discovered many other types of cells in the immune system and came up with an important term-antibodies. Moreover, after years of research, he discovered that the immune system existed as early as 500 million years ago when the species differentiated.

It turns out that the immune system has existed for so long, and it has always been desperate and brave enough to make the species on the planet evolve and continue to thrive. They are like a peacekeeping force that is always vigilant and ubiquitous in the Carnival of Life.