Worth knowing about the immune system

Hardly any other part of the organism is discussed as often as the immune system: be it in the many more or less (in) qualified discussions about the pros and cons of vaccinations, or with countless tips for strengthening the immune system. "My PET" spoke to Dr. Michael Leschnik from the University of Veterinary Medicine Vienna on how the immune system works and what its tasks.

Colloquially, the immune system is often referred to as "body police". What is the primary task of the immune system?

Dr. Michael Leschnik: First, the immune system has a monitoring task and, in a figurative sense, an execution task. It should recognize intruders from the outside as well as changes in the body and fight as early as possible. For the most part, one thinks primarily of the fact that the immune system deals with pathogens that invade the organisms from the outside, with foreign proteins of viruses, bacteria or fungi. It is often forgotten that the immune system also plays an essential role in tumorigenesis and prevention. Today, it is known that in the animal as well as in the human being in the course of life tumor cells arise very early on, which are eliminated by the immune system before a cancer arises from it.

What is that, the immune system? We are not dealing with a tangible single organ, but with an absolutely indispensable body function?

Dr. Michael Leschnik: This system, which consists of relatively many interlocking parts, is very complex and undergoes a development that already starts with the puppy, who by no means comes into the world with a fully-fledged immune system. The immune cells are present at birth only to a certain extent and with partly incomplete function, and, moreover, the immune system of a newborn puppy has of course not experienced much. First of all, there is almost no immune memory. That's why the puppy has to get the maternal antibodies in the first one to two days of life with breast milk. This is an important process, because only in the first days of life these antibodies can enter the pancreatic system via the mucous membrane of the gastrointestinal tract. Some of these mother's antibodies work into the twelfth or thirteenth week of life and then slowly break down, while the immune system begins to produce its own antibodies against the pathogens it deals with.

How can you imagine these antibodies?

Dr. Michael Leschnik: These are small proteins that usually look Y-shaped. Each antibody forms its own structure with this Ypsilon, which fits to a certain possible intruder. This means that certain antibodies only work against certain pathogens. If such an antibody hits its proper pathogen, it acts like an adhesive. It binds to this pathogen, marking it, so to speak, and this mark eventually becomes the signal for the activation of the further immune system. If the pathogen is eliminated, the immune system stops the production of the corresponding antibody after a short time, because it is currently no longer needed. But it does remember this antibody for a while, and if the organism were then confronted again with the corresponding pathogen, this antibody would be formed much faster and to a great extent. That's the effect we take advantage of in the vaccine. With the vaccination we present to the immune system killed or attenuated pathogens. Then the immune system forms antibodies and at the latest after the 2nd or 3rd vaccination, ie at the end of the basic immunization, a much stronger, faster and more extensive immune response takes place. Depending on the vaccine and disease, these antibodies will last for several months to a few years. This is the basic principle of a vaccine that provides protection against a natural pathogen that could invade the organism.

What happens in the body when it comes to contact with such a pathogen? How does the immune system develop its defenses?

Dr. Michael Leschnik: First of all, it is important to know that the immune reaction in both the fluids, e.g. in the blood, and in the tissues of the body takes place as well as on the body surface. There are immune cells and antibodies that are active in the area of ​​the mucosal surfaces, but they are only the first barrier that sets up the immune system to fend off the intruder. Behind it are the components of the immune system, which spread over the blood stream very quickly throughout the body and can be effective anywhere. Some viruses that we know in dogs and cats are taken up via the mucous membranes. However, this mucosal barrier can be overcome extremely quickly. This first defense on the mucous membrane, especially in the case of viruses, means that they are first recognized by an antibody, labeled and presented to the immune system. Under certain circumstances, however, they can not yet be destroyed. It creates a kind of fight between the different fractions of the immune system and the intruder, which of course does not remain idle. He wants to multiply and not be destroyed, so he trains mechanisms to either escape the immune system, make himself invisible, or look like he's always there and part of the body. Depending on when the immune system can eliminate the pathogen, the disease eventually develops or not. If the immune system can eliminate the pathogen very early, nothing happens that would be visible from the outside, but of course the organism forms the corresponding antibodies. If the organism becomes ill and becomes healthy again, the immune system has won the argument. If this fails, the whole ends either with a permanent illness or, in the worst case, with death.

Does that mean the immune system needs much more than the antibodies for this life-saving battle?

Dr. Michael Leschnik: The first is the antibodies, the second the cells, the so-called cellular defense. In addition, there are many other parts of the chemical-based immune response. For example, the defense cells form proteins that act directly on the pathogen, which can immobilize or destroy it, for example. The two major parts of the immune response, however, always work together. The antibodies are already formed by the immune cells. In addition, there are other cells that primarily have morgues that directly pick up and destroy the pathogens, cells that have labeling properties, or cells that produce substances that harm the pathogens. This is an exciting interaction: Each of the cell types of the immune system has different functions.

Why does the blood count in inflammation result in increased levels of white blood cells, leukocytes?

Dr. Michael Leschnik: The increased levels occur because the immune cells multiply in an inflammation - although we may even have fewer leukocytes at the very beginning of the disease in the blood. It can be imagined as follows: The body is in a peaceful twilight sleep, so to speak. Suddenly something happens, for example in the lungs. First of all, many immune cells migrate from the bloodstream into the lungs. At this time, at the onset of the disease, which is usually accompanied by acute fever, there are even fewer immune cells in the blood. Now, however, the bone marrow, which is responsible for the formation of these immune cells in the body in the adult animal, will produce more of these cells. From the bone marrow, the newly formed cells enter the bloodstream, where we now find many young immune cells. In the course of the disease after a few days, we then find the typical high number of white blood cells.

This entire process of immune defense can also be disturbed. What can lead to the immune system not working optimally?...

Illnesses that require intensive treatment. Allergies are also the result of a misguided immune system. Here suddenly a very massive reaction takes place against a so-called allergen, ie against a substance or part of a substance, which in itself does not have to be harmful, but the misguided immune system decides that this is an intruder and must be fought. Basically, any banal activation of the immune system can trigger such reactions, simple infections, chemical substances, sometimes even medications, and possibly also a vaccine. In the end, the triggers can often not be proven, and of course one can not say that vaccinations are in principle bad, there are so many immune reactions. On the other hand, one demonstrable fact is that the number of serious infectious diseases from vaccinations has decreased significantly.

Strengthening the immune system - that is already a nearly proverbial term today. What does that mean?

Illnesses that require intensive treatment. Allergies are also the result of a misguided immune system. Here suddenly a very massive reaction takes place against a so-called allergen, ie against a substance or part of a substance, which in itself does not have to be harmful, but the misguided immune system decides that this is an intruder and must be fought. Basically, any banal activation of the immune system can trigger such reactions, simple infections, chemical substances, sometimes even medications, and possibly also a vaccine. In the end, the triggers can often not be proven, and of course one can not say that vaccinations are in principle bad, there are so many immune reactions. On the other hand, one demonstrable fact is that the number of serious infectious diseases from vaccinations has decreased significantly.

Strengthening the immune system - that is already a nearly proverbial term today. What does that mean?

Dr. Michael Leschnik: The best way to strengthen the immune system is to always keep it active. A completely sterile environment weakens the immune system, therefore, dealing with the environment and with diseases is not necessarily something negative. Chemical substances that help the immune system in the event of illness, for example, are classic drugs - such as antibiotics - that weaken or kill the pathogen. Vitamins or trace elements support the metabolism necessary for the immune system and can, especially if the system is weakened, have a supporting effect. But a well-functioning immune system, which one must honestly say, we can hardly improve by the administration of any additional preparations. Strengthening the immune system works when it is not quite up to par. Of course, chronic stress, which the animal can not escape, is to be judged negatively. On the other hand, short-term stress is activated and does not have to be detrimental in principle if the whole thing runs in moderation. Also, an infection is stress for the body, but activates and trains the immune system, for example, during vaccination. A trained immune system reacts faster and more effectively, while an overloaded immune system does exactly the opposite. It is not always easy to find the right path. We must avoid fatal and lethal diseases that may be harmful to humans in our animals, but we should only vaccinate against the diseases that really occur and that are relevant to the individual animal. Many vaccinations are done properly for more than a year, so it is not compulsory to vaccinate against every disease every year. The prerequisite, of course, is that the animal does not live in a region where this disease is particularly common. Basically, a single decision has to be made for each patient.

Dr. Leschnik, thank you for the interview!