The theory of total immunity
Immunologist Ravshan Ataullakhanov – about antibiotics, phagocytes and protective properties of blood
Today we will try to consider the general principles that are used to protect our body from some misfortunes. Let's clarify what these misfortunes are. Protection is called immunity, and it is available in all multicellular. It protects against those living beings that are not visible to the eye, you can't feel their touch, you can't smell them. That is, these are invisible living beings who tend to invade our body, parasitize, use it for their own purposes, and we are obliged to defend ourselves. This protection is available to any multicellular, starting with the smallest, consisting of only a few hundred cells, and ending with as large as we are, or even more, where there are 100 trillion cells.
What ideas and solutions did nature use to protect? The simplest idea is simply not to let in, to protect yourself from any intrusion of any small invisible creature, to make an impenetrable bathysphere, a bathyscaphe. But this idea does not pass, because a living being must receive food from the outside world, must exchange gases, receive oxygen by giving off carbon dioxide. It must perform complex behavioral functions, run away from danger, catch, catch up with food, engage in sexual relations, reproduce. It is impossible to do all this in a bathysphere, in a bathyscaphe. Therefore, the idea of fully protecting yourself does not pass, it is not feasible.
But the boundary of the body with the outside world is made very strong and impenetrable for almost everything, for any small, the smallest living being, it is impenetrable. What are these boundaries? This is the boundary at which it is necessary to absorb or absorb food substrates, this boundary is the surface of the intestine. Every surface is called an epithelium, a surface layer. The other boundary is the surface where gas exchange takes place. These are our lungs, the respiratory system. But there are also borders that are much smaller in size.
The digestive boundary is huge because we need a lot of food substrate. We have it about 300 square meters in size, and it all needs to be protected. Respiratory – 70 square meters. In order for this boundary not to be a bathysphere, a bathyscaphe, but to function, nature made it very thin so that substances, gases and soluble molecules could be transported through it. Very thin – the size of one, at most a few cells thick. If we translate this into ordinary metric units, then this is about one tenth of a millimeter. That is, the thickness of this border is extremely small. And then food substances can be transported through it. And the respiratory border is even thinner, it is half a micrometer. This is a thousand times less than a millimeter, and then it is possible to transport gases.
But how to make such a border strong, and even protect it from invasion? Nature made it strong by creating a continuous network of the thinnest fibers with a thickness of about 40 nanometers inside this boundary. Imagine a net made of rope, very strong, synthetic, braided, but very thin. This gives the strength of a surface consisting of only one layer of cells. Thus, the boundaries are huge, thin, flexible, functional, transparent to the molecules that need to be transported, but strong.
The next idea is to water these borders with antibiotics so that microorganisms, coming into contact with our border, immediately die. And the cells forming the boundaries secrete many different substances that serve as antibiotics, suppress and kill microorganisms. This enhances border protection. This is an idea that nature uses: in our body, about a hundred different substances perform the function of antibiotics.
The next idea that the body implements is to strengthen the protection of borders with the help of mobile, mobile cells – a special type of cells that are well armed and able to kill any miniature enemy and even devour it. They are called phagocytes and dendritic cells – these are two types of numerous cells. They are not born in the border tissue, but specifically come there and live permanently. These mobile patrols in the border fabric strengthen protection, since they can kill the invading enemy and move to where they are most needed, to the part of the fabric where the invasion occurred.
Another idea that nature implements: nature has provided every cell of our body with molecular sensors, sensors that can sense infection. If an infection comes into contact with a border cell or a cell already lying in our tissues, then the cell recognizes this with the help of sensors and carries out two reactions. Both reactions are protective: the first is the production of substances that kill the infection, and the second is the production of chemical signals that inform other cells about the attack. And these signals, spreading from the cell that has encountered the infection, are crawled by the very mobile patrols that are able to pick up these signals and know where to crawl: towards the chemical signal to which they react. This is called chemotaxis of cells, they move to where the invasion occurred.
If there are not enough local forces, fortified borders, mobile patrols, alarm systems, antimicrobial poison production systems… In fact, it is sufficient in the vast majority of cases. But if suddenly the enemy turned out to be very cunning or there were so many of them that he slipped through these redoubts, he could not be destroyed, then centralized protection is connected: local forces failed.
The reserves of centralized protection are in the blood. And the cells forming the wall of blood vessels are able to regulate the permeability of these blood vessels for substances and for cells. The substances and cells circulating in the blood are an almost unlimited reserve of the protection that will come where it is needed, and at the moment when it is needed.
How will this reserve know about it? The cells of the vessels closest to the site of the invasion of infection will change in such a way that they will make the permeability of the vessel for substances and cells increased. And it is in this place that large protective molecules will come out of the bloodstream into this tissue and help protect themselves. It is in this place that special protective cells will come out, which will also either kill the infection, or kill and absorb it, exterminate it completely. There are countless numbers of these cells circulating in the blood. Moreover, they are constantly updated and replenished from the bone marrow. This is the phenomenon of the release of large molecules that protect us from infections, from everything else in the place where they came out, as well as cells that have a protective function, we know as inflammation. We know the signs of this inflammation, but at the heart of this protection is the exit of molecules and cells from the blood to the place where it is necessary to protect.
It is very important to highlight the central idea here, to voice that all cells and every cell of our body know how to defend themselves and defend themselves. The idea that only special types of cells and a special system – the immune system – are engaged in this is wrong. Everyone is engaged in protection, but immune cells are able to do it better than others, they are experts in this matter. Every cell has protective properties and functions, even such simplified cells as erythrocytes and platelets also have the ability to defend themselves, they also have sensors that recognize infection, they have substances that can protect us from infection.
This means that all cells of the body participate in protection and can do it, including the liquid phase of the body – blood and the liquid part of the blood, which with large molecules goes to the tissue where it protects us with the help of complement factors. This means that the liquid phases of the body also protect us. So, all cells and all fluids participate in the defense against the invasion of strangers or from invading strangers. And this is a kind of theory – the theory of total immunity.
Ravshan Ataullakhanov – Doctor of Medical Sciences, Professor, Head of the Department of Immune Biotechnology, Head of the Laboratory of Immune Activation of the Institute of Immunology of the FMBA of Russia, Professor of the Department of Immunology of the Faculty of Biology of Lomonosov Moscow State University.
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20.07.2017