Mention red blood cells, readers and friends will definitely think of oxygen transport immediately. Yes, the numerous red blood cells in our bodies have established a life channel for us to transport oxygen. But are the large numbers of red blood cells in the body only involved in respiratory functions, delivering oxygen to the body?
It turns out that no, in addition to oxygen transport, further research by scientists on red blood cells found that red blood cells are also involved in the body's immune regulation. (Were you surprised?) After all, there are no red blood cells involved in the immune regulation that everyone learned in high school.
The huge number of red blood cells in the body contributes to all aspects of our life activities, so let's take a closer look at these little heroes!
Red blood cells that transport oxygen with life
The blood that flows through our bodies contains plasma and blood cells, and the largest number of blood cells is our red blood cells.
Image source search.creativecommons.org
When we describe the morphology of red blood cells, we usually use the shape of a concave round cake in the middle (I believe that everyone is already familiar with its morphology, after all, high school organisms have not touched it less... This is the result of its abandonment of the nucleus and many organelles in order to transport oxygen, and it is this form that allows red blood cells to have a place to place hemoglobin and bind oxygen to the greatest extent, but it is precisely because of the abandonment of the nucleus that the average lifespan of red blood cells is only about 120 days, and it can be said that red blood cells use their lives to transport oxygen!
Image source hippox
Why do red blood cells transport oxygen? Because there is hemoglobin! The oxygen obtained by the body through respiration is first dissolved in the lipids of the alveolar surfactant, and then dissolved in the plasma of the blood through the alveolar wall and the capillary wall around the alveoli. The oxygen in the plasma binds to the hemoglobin in the red blood cells after free diffusion into the red blood cells, forming oxygenated hemoglobin, which is transported through the systemic circulation throughout the body.
Hemoglobin, image source search.creativecommons.org
When blood with a high partial pressure of oxygen flows through the capillaries between tissues, the oxygen in the blood quickly separates from hemoglobin and spreads through the capillary wall into the tissue cells to be utilized. This is the process by which red blood cells transport oxygen as they are known. With the extensive work done by scientists on red blood cells, another function of red blood cells has also been discovered, that is, to participate in the body's immunity.
Sacrifice your own early warning red blood cells
As early as 1930, scientist Duke discovered that trypanosomiasis can adhere to human red blood cells when antiserosal and the like are present, and the ability of red blood cells to adhere to trypanosomes varies from person to person. In 1953, Nelson discovered that human red blood cells could bind to specifically conditioned treponemal syphilis and Streptococcus pneumoniae. It is speculated that there are immune adhesion receptors on the membrane of red blood cells, which can promote the phagocytosis of white blood cells (I believe everyone knows the role of white blood cells in the body's immunity, especially phagocytes... In simple terms, scientists at this time have already linked red blood cells to the body's immune regulation.
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Under such speculation, many scientists in different countries have studied the role of red blood cells in the body's immunity. The latest research has found that red blood cells can bind to fragments of DNA, which in turn play an important role in the body's immune regulation. The study was published on October 20 this year in the heavyweight journal Science-Translational Medicine.
Image credit: PubMed
Previous scientists have found that red blood cells can also participate in the body's immune regulation, but the specific regulatory mechanisms in which they are involved are not clear. In the newly published study, scientists took red blood cells from sepsis patients and patients with covid-19 and found that on the surface of their red blood cells there is a protein called TLR9 (Toll-like receptor), which binds to free CG-rich DNA fragments that are generally derived from mitochondrial DNA released by bacteria, malaria parasites, or other damaged cells. When a patient is infected with bacteria or viruses, the DNA of the bacteria or the mitochondrial DNA fragments released by the damaged cells bind to the TLR9 on the surface of the red blood cells, resulting in changes in the morphology of the red blood cells. (From a round cake with a depression in the middle to an omelette with multiple bulging buns...) ）
Changes in the morphology of red blood cells, image source "Science - Translational Medicine"
Changes in the morphology of red blood cells prompt TLR9 to bind to more DNA fragments, eventually rendering red blood cells unrecognizable, like a ball full of pustules. It is this abnormal appearance that arouses the body's alertness and triggers an immune response. The phagocytes roared to clear the pathogen, and at the same time, they also removed these red blood cells that combined dna fragments, and the red blood cells could be said to be guarding the body in a suicidal way!
Phagocytes, image source search.creativecommons.org
Of course, the removal of red blood cells also means that the number of red blood cells that can work normally in the body is greatly reduced, which explains why severe patients in intensive care units often have symptoms of anemia. Recognizing this important function of red blood cells, we may be able to further investigate ways to combat acute inflammatory anemia, or to find the cause through the clues provided by red blood cells.
Image source Science - Translational Medicine
How about the hard-working red blood cells in the body, do you love them? Isn't it like you're working very hard?