Immune system: defender or bloody rubble?

Natural security agencies
Boris Zhukov, Daily Magazine 

Admirers of the state are very fond of comparing it with a complex living organism, seeing in the latter the ideal of the state system. In fact, our body, for example, consists of several tens of trillions of relatively independent individuals-cells grouped into friendly labor collectives of tissues and organs. In this ideal state, everyone does their job without trying to take the place of the boss or expand their own powers at the expense of the powers of a colleague. The cell's "career" is limited to the period of its maturation, which can be likened to getting an education in human society. Once having started its duties, the cell will work in the same place in the same "profession" and "position" for the rest of its life, without even thinking about a different fate: after all, it has no interests of its own, different from the organism. The job of some cells is to die for the sake of the interests of the organism – and they go for it willingly, without grumbling and without asking why they had such a share. Moreover, the organism can order any of its cells to die at any moment – and it will meekly chop itself into pieces that will still be useful to those who remain alive. A wise organism regulates other aspects of the life of its subjects: it tightly forbids some cells to reproduce, for others it makes reproduction the only content of their life. Needless to say, in this ideal state there are no elections, the struggle of parties, the opposition, public discussions and the media. In general, the dissemination of information in it does not go beyond the functional necessity: each subject is informed exactly as much as is required for his successful work. He simply will not perceive any information not addressed to him, as we do not perceive radio waves.

We will talk about how this ideal is applicable to the available human material – wayward and self–serving, immensely valuing his insignificant life and always trying to make it better - sometime separately. Now we are interested in only one particular question. An ideal State cannot do without a large, sophisticated and highly empowered system of State security. It also exists in a living organism – this is the immune system, whose task is both to identify and destroy foreign elements that have penetrated into the body, and to timely eliminate their own subjects, whose behavior, one way or another, deviates from the prescribed.

We will not go into details of how this system is organized – suffice it to say that its structure is very complex. It has experts identifying the one being developed, and destruction groups, and a security check service... The efficiency of this system, of course, is not absolute – we suffer from infectious diseases, our cells sometimes degenerate into cancerous ones – but it is still quite enviable. Especially in cases when she has enough enemies to fight with.

However, the way of life of modern citizens of civilized countries is such that there are sometimes categorically not enough enemies. Boiled water, pasteurized milk, disinfected air, helminths are generally forgotten that there are such, and all known microbes in the toilet are killed by another patented remedy. A huge army of experts, operatives and special forces is rushing around. However, even in this situation, they do not try to "steer" digestion, cover the work of the lungs and take financial control... that is, energy flows, but meticulously and hopefully check any cell, any molecule that happens to be on the borders of the body.

Whoever is looking, he will always find: often this intense search ends with the fact that the stagnant idle system pounces with exaggerated fury on a completely innocent alien organic particle: a grain of cereal pollen, a microscopic piece of cat hair, a crumb of chocolate... The potential intruder has not even crossed the boundaries of the body, he is on the mucous membrane of the mouth or nasal cavity, and the blood is already filled with myriads of alarmed immune cells and a myriad of immunoglobulins emitted by them. The mucous membranes swell, fill with blood, the nose is sore, the throat is itchy, the eyes itch, blisters appear on the skin in places. In particularly severe cases – when the general mobilization to fight the detected enemy is most successful – the body may even die from anaphylactic shock. And to hell with it – when it comes to security, we don't feel sorry for anything!

This syndrome is called allergy in medicine. It is firmly established that it is based on a completely disproportionate, grotesquely exaggerated immune reaction to some completely harmless external agent–an allergen. However, scientists have not yet been able to understand why the immune system suddenly qualifies this or that ordinary substance as a terrible threat and reacts to it so violently.

However, an allergen is still a foreign substance, a "foreigner" and therefore suspicious by definition. But it also happens that the immune system, underloaded with enemies, begins to take a closer look at its own cells and tissues. For example, the glandular cells of the so–called islets of Langerhans in the pancreas - what do they do, what benefits do they bring to the fatherland? They live for their own pleasure at the public expense, and as their contribution to the common cause, they throw some unfinished protein into the blood, prompting cells of all tissues to absorb sugar from the intercellular medium. Why, this is direct sabotage! Sugar is a valuable strategic product, and these worthless islet cells stimulate its squandering. Okay, we'll deal with them now...

And they understand. Fortunately, the immune system has the powers not only of investigators and prosecutors, but also of judges whose verdict is not subject to appeal, but there is no independent court, public proceedings and other harmful inventions in an ideal state-organism, of course, there is no. Immune cells simply eliminate unrequited "pests" with the same determination and lack of doubt with which they destroy the infection that has penetrated into the blood. As a result, a person reliably protected by these zealous guardians suddenly has incurable diabetes mellitus at the most blooming age, and he will have to support himself with insulin injections for the rest of his life – that is, to inject from the outside the very product that the destroyed islet cells produced.

In other cases, other tissues fall under the suspicion of security zealots and public interest – and this results in systemic lupus erythematosus, multiple sclerosis and other equally serious conditions. Such diseases caused by the attack of the immune system on the body's own tissues are called autoimmune. Their frequency, as well as the frequency of allergy diseases, has doubled over the past 30 years. And medical science, which has so successfully tamed infectious diseases, cannot yet find the means to cope with this scourge.

It is also unknown by what signs the ultra-sensitive immune system chooses "enemies" among the tissues of the body. But there is one tissue whose characteristic antigens invariably provoke the fury of our internal security system. This is the intellectual elite of the body – the tissue of the brain and spinal cord. In cases where the immune system comes into contact with cells of the central nervous system, it immediately regards them as enemies and proceeds to destroy them. That is why a point rupture of a tiny blood capillary, which in any other tissue would have absolutely no consequences, turns into a severe disease in the brain – a stroke.

However, under less dramatic circumstances, such contact is impossible: the cells of the immune system, which have the authority to enter any nooks and crannies of the body and penetrate through any barriers, are completely deprived of access to brain tissue. Even their specific products – antibodies and other proteins - cannot penetrate here.

For such "immunity from immunity" brain tissue has to pay defenselessness. Quite a few infectious diseases – mainly of a viral nature – exist only because their pathogens have the opportunity to hide from the immune system inside neurons (other viruses try to hide in other cells, but unsuccessfully: there are specialist cells in the immune system that can force an infected cell to present viral antigens). For example, a person gets rabies only if part of the viruses introduced during the bite gets into the peripheral nerves, through which they gradually reach the central nervous system. Viruses that have not had time to hide in the inviolable tissue are quickly destroyed by the immune system – and there is no doubt that it would have coped just as successfully with those that have penetrated the brain if it had access there.

However, evolution ordered otherwise. Rabies or polio is still not threatening everyone. But the omnipotence of the security service, it seems, is in principle incompatible with successful intellectual activity.

Portal "Eternal youth" http://vechnayamolodost.ru17.09.2009