Children's immunity: features of formation, signs and causes of weakened functioning. How is specific immunity created? When does a child’s immunity mature?
Without immune system human life would be impossible. The immune system is so perfect that it is capable of not only recognizing a foreign body (distinguishing its biomolecules from its own), but also isolating and destroying it inside the body.
Innate immune system
The innate immunity in our body is constantly in “working” mode; it is the very first one that encounters all pests and eliminates them. Job innate immunity begins after the birth of the child, however, not in full force. The complete strengthening and development of immunity occurs gradually, which is why it is very important to feed the baby with breast milk and harden it.
Immediately after birth, the immune system is already able to protect the child from such bacterial diseases such as tonsillitis, bronchitis, otitis media, etc. When an infection enters the body, the first obstacle it encounters on its way is the mucous membranes, which have an acidic environment that is not favorable for its development. As soon as the infection reaches the mucous membranes, bactericidal substances begin to be released. It is the mucous membranes that trap and eliminate most aggressive microorganisms.
If for some reason the mucous membranes have not coped with their task, and the infection has gone inside the body, it encounters the next obstacle - specialized cells, phagocytes, which are found both on the skin and mucous membranes, and in the blood. Together with special protein complexes, phagocytes provide bactericidal and antiviral effect, thanks to which only 0.1% of all viruses and bacteria survive.
Specific immune system
The specific immune system, or as it is also called acquired, is developed gradually. The body gradually learns to distinguish “friends” from “strangers” thanks to immunological memory. This process is only possible through contact with bacteria, viruses and microorganisms. This protection is formed by two very important and closely related factors - cellular (T- and B-lymphocytes) and humoral (immunoglobulins - antibodies). The cellular factor remembers the foreign substance, and when it encounters it again, it quickly and effectively destroys it - this is immunological memory. This is exactly how they work - a strain of the virus is purposefully introduced into the body so that the T- and B-lymphocytes remember the virus and, when they encounter it again, quickly destroy it. T-lymphocytes destroy the virus on their own, and B-lymphocytes secrete special antibodies - immunoglobulins. You've probably seen them more than once in test results - they come in 5 types: IgE, IgA, IgG, IgM, IgD.
Immune system in newborns
In the process of life, a person constantly encounters aggressive microorganisms and produces immunoglobulins to hundreds of such foreign bodies. The baby’s body is much more vulnerable in this regard, since the acquired immunity is still completely “inexperienced.”
The formation of the immune system in a newborn begins approximately at the 3-8th week of pregnancy, it is then that the child’s liver is formed, which begins to secrete those same B-lymphocytes. Somewhere between weeks 5 and 12, the thymus (the thymus gland located at the top of the sternum) forms, where T-lymphocytes begin to form and train. At the same time, the first IgG immunoglobulins. After the 32nd week of pregnancy, B lymphocytes secrete the entire complex of immunoglobulins, which will help protect the baby’s body in the first months of life. Once the spleen is formed (at approximately 21 weeks), lymphocytes begin to be released. However, the lymph nodes that should retain foreign bodies, will be able to fully protect the child’s body only by the age of 7-8 years.
Remember! Not proper nutrition, infectious diseases in the first 20 weeks of pregnancy can negatively affect the formation of these organs! Therefore, it is very important to avoid contact with sick people, flu, avoid hypothermia and follow a balanced diet.
The first critical period in the development of the immune system
This marks the moment of birth when the baby's immune system is purposefully suppressed. The whole point is that, passing through birth canal, the baby encounters a mass of new bacteria, and when it is born, the number of new bacteria is in the billions. If the baby’s immune system worked the same way as an adult’s, the child’s body simply could not withstand such a “collision” with the new environment. That is why by the time of birth the baby’s immune system only works at 40-50%. Because of this, the child’s body is very susceptible to viruses and bacteria; his health is maintained only thanks to immunoglobulins received from the mother. After birth, the baby’s intestines begin to be “populated” with beneficial intestinal bacteria, baby is eating special mixtures or breast milk, receiving everything necessary for the development of the immune system. It is worth noting that important here is, which is recommended to be given to the baby immediately after birth before the milk comes in.
The second critical period in the development of the immune system
By approximately 6 months, all antibodies received from the mother are completely gone from the body. By this time, the baby’s body should already be producing immunoglobulin A on its own (but it does not have memory, so vaccinations completed at this age must be repeated). In the period from 3 to 6 months, it is necessary to harden the baby; after bathing in water with a temperature of 36-37 degrees, it is recommended to pour water on the child 1-2 degrees lower. Every 5 days it is recommended to reduce the water temperature by 1 degree and bring it to 28.
The third critical period in the development of the immune system
This period occurs in the second and third years of a child’s life. During this period, the active development of specific immunity occurs - the baby comes into contact with other children, adults, animals, and begins to attend nurseries and kindergartens. During this period, children get sick much more often, and often one disease replaces another. There is no need to worry here, this does not mean that the child has poor immunity, he just encounters new viruses and bacteria - this is a necessary stage in the development of acquired immunity. Normally, a child gets sick up to 8-12 times a year.
It is worth noting that at this age there is no need to give the child immunostimulating drugs - they have many contraindications, side effects In addition, they will lower the child’s natural immunity.
The fourth critical period in the development of the immune system
This is the last period and it occurs between 5-7 years. At this age, the child already has T- and B-lymphocytes almost at adult levels, however, immunoglobulin A is still in short supply, so children at this age often acquire chronic diseases of the upper respiratory tract. At this age, it is necessary to give your child multivitamin complexes during the cold season, but it is better to check with your pediatrician which complexes to give your child. It is worth giving immunostimulating drugs only after an immunogram has been completed, which will show which part of the immune system is suffering.
A child is born with a very weak immune system. It produces immune cells, but they are not enough to build a reliable barrier to repel the attack of viruses and bacteria. Therefore, the protection of the child’s body is based on immunoglobulins O (they are able to recognize “strangers” and fight chronic infection), which the baby receives from the mother in utero in the third trimester of pregnancy. If the expectant mother is healthy, then the child is reliably protected by immunoglobulins; if not (even common acute respiratory infections are taken into account), placental insufficiency may occur, and the baby will not receive enough lifesaving cells. However, antibodies obtained in utero only protect for three months little man from diphtheria, polio, measles, rubella, meningitis, scarlet fever, rheumatism and other very dangerous illnesses, but only on the condition that the mother had been ill with them or, at least, was vaccinated against these diseases.
By the fourth or fifth month of a child’s life, the production of his own immunoglobulins in his body is gradually improving. True, these are only immunoglobulins M, which are the first to join the fight against invading “agents”, but, alas, do not protect the baby from infectious diseases. Fortunately, up to a year, it is more or less reliably protected by immunoglobulins A received in breast milk, which are responsible for the local immunity of the nasopharynx. Most dangerous period for the child’s immunity - from 6 months to 1.5-2 years. At this time, maternal antibodies gradually lose their strength, and the production of their own has not yet been established.
The number of own protective cells of type A begins to grow in children only after 4 years of age, so immunologists advise sending a child to kindergarten no earlier than 4 or 5 years. At 5-6 years of age, formation immune cells continues rather slowly, which explains the susceptibility of preschoolers viral infections.
Only by the age of 7 are the indicators of immunoglobulins M, O, A in a child approaching adult norm- This is why experts recommend sending children to school after 6 years. By the way, full production of the antihelminthic immunoglobulin E begins no earlier than 7 years, so helminthiasis is the scourge of preschool children.
It would seem that in adolescents, the immune system should finally “grow up”, but it is hampered by... hormones, the activity of which temporarily weakens the body’s defenses - in teenagers, sensitivity to tuberculosis increases, and the risk of developing chronic diseases. As soon as hormonal background young people are established, the immune system is strengthened. The last chords in the formation of protective forces occur in the period of 18-20 years, but the immune system must always be maintained and strengthened.
Harmful for the immune system:
Swaddling
Research by neonatologists (doctors who care for babies under three months of age) shows that swaddling may interfere with the development of immunity. If a child is constantly wrapped tightly, his body gets used to the warmth, and even the slightest breeze or temperature change is enough to cause hypothermia. The immune system of such a baby weakens, which means it cannot actively resist pathogens.
Bad habits of parents
It has been proven that even passive smoking destroys vitamin C in the body. As is known, ascorbic acid responsible for our adaptive capabilities and increases resistance to infections.
Immunostimulants
Immunologists are unanimous: drugs that boost immunity are harmful if parents prescribe them to their children on their own. This even applies to echinacea, because taking medications based on this plant is recommended only when purulent processes- otitis media, sinusitis, etc. With a common cold, Echinacea can create an imbalance in the functioning of the body's defenses. In addition, immunostimulants can provoke allergies, since most of them are made from herbs.
Sterility
If you sterilize dishes and toys, wash the floor by special means and boil diapers, the baby’s body will not learn to produce antibodies against common viruses and bacteria that will be encountered in kindergarten and school.
Intelligent press
Modern school curriculum plus additional classes on the development of intelligence - a solid load on children's body, including the immune system. Mechanism of influence of constants brainstorming is this: children burdened with science get tired, often get sick, and this, in turn, harms the formation of a reliable protective system.
Good for immunity:
Mother's milk
With it the child receives everything he needs nutrients, vitamins and microelements, as well as very important components - antibodies. Children who are breastfed are less likely to get sick and suffer less from allergic diseases, otitis, pneumonia. The longer you breastfeed, the greater your baby's resistance.
Cold and movement
Experts consider these factors to be the best immune stimulants. You will help your child a lot if you teach him to sleep with open window at any time of the year, you won’t clutter your baby’s body unhealthy sweets and once again you will go out with him to run and jump on fresh air.
Fermented milk products
Immune cells that synthesize immunoglobulins are formed in the intestines, so malfunctions in the functioning of this organ (constipation, disorders) harm not only digestive system, but also immunity. The best way strengthen protective function organism - to inhabit gastrointestinal tract beneficial microflora, bifidobacteria and lactobacilli of fermented milk products - yogurt, kefir, acidophilus milk. Sometimes a disadvantage beneficial bacteria causes the development of allergies.
Diseases
The immune system needs training in the form of... diseases. However, not every ailment helps strengthen the immune system, but only those (for example, acute respiratory infections, acute respiratory viral infections) that do not cause severe complications and do not turn into chronic form. The main thing is that training does not become constant, depleting your defenses.
Immunity - most important property human body. Immune defense is complex and multi-stage, it begins to function in the prenatal period, improves and develops continuously throughout life, protects the body from the penetration of substances foreign to it.
There are two main types of immunity: hereditary (species) and acquired (individual). Species immunity makes a person immune to many animal diseases (for example, canine distemper) and is inherited by subsequent generations. Individual immunity is developed throughout the life of each person and is not inherited.
There is also a distinction between active and passive immunity. Active immunity is produced by the body itself after an infectious disease or the administration of a vaccine (vaccination) that contains weakened or killed infectious agents. Passive immunity appears after the introduction of ready-made antibodies into the body, which are contained in serum (as well as the transfer of antibodies from mother to child during pregnancy through the placenta). Active immunity is formed over time and lasts a long time, passive immunity appears immediately, but soon disappears. Accordingly, active immunity (vaccines) is used for prevention, and passive immunity (serums) is used for the treatment of infectious diseases.
Immune response
Any substance whose structure differs from the structure of human tissue is capable of causing an immune response. It is not specific and specific. A non-specific immune response is the first stage in the fight against infection. This mechanism starts immediately after the microbe enters the body, is almost the same for all types of microbes and implies the primary destruction of the microbe and the formation of a focus of inflammation. The inflammatory response is a universal protective process that is aimed at preventing the spread of a microbe. Not specific immunity determines the overall resistance of the body.
The specific immune response is the second phase defensive reaction: the body recognizes the microbe and develops a special defense against it. The specific immune response, in turn, is also of two types: cellular and humoral. The body can neutralize a foreign substance (antigen) by producing active cells that capture and digest the antigen. This is cellular immunity. The main elements of the body's immune system are special white blood cells - lymphocytes. If the antigen is destroyed with the help of special chemically active molecules - antibodies, then we're talking about about humoral immunity (from the Latin “ humor" - liquid). The role of antibodies is performed by proteins (immunoglobulins) in the blood.
Features of newborn immunity
A child's immunity begins to develop in the womb. During this period, the main role is played by heredity, that is, the characteristics of the immune system of the parents. Besides great value has a successful pregnancy, lifestyle expectant mother(the nature of her diet, compliance with the doctor’s recommendations).
The synthesis of the fetus's own antibodies begins around 10-12 weeks of pregnancy. However, the fetus is able to produce only a limited amount of immunoglobulins. The basis of immunity in newborns is the mother's antibodies. The process of transfer of antibodies from mother to fetus occurs mainly at the end of pregnancy, so premature babies are not sufficiently protected from infections compared to babies born at term.
The state of the child's immune system depends on many factors, including how the baby is fed. The role of breast milk protective properties which is well known, is especially great. It has been proven that breastfed children are less likely to get sick infectious diseases, since in breast milk contains many maternal antibodies and special cells that can absorb microbes. True, antibodies obtained in this way act only in the intestines. They protect the child well from intestinal infections. In addition, the proteins of mother's milk are devoid of allergenic properties, so breastfeeding is the prevention of allergic diseases.
Interestingly, the newborn’s immune system is in a state of physiological suppression. This is a natural protective reaction of the body, the meaning of which is to prevent the development of violent immune reactions that could develop when a newly born baby comes into contact with a huge amount microorganisms in the environment. The first 28 days of life are considered the first critical period in the formation of the immune system. At this time, the baby is especially susceptible to viral infections and the effects of microbes. In addition, another feature of the immunity of children in the first months of life is the inability to limit infection: any infectious process can quickly spread to the entire child’s body (this is called generalization of infection). That is why it is necessary, for example, to take very careful care of the healing umbilical wound.
The second critical period is 3-6 months of life. Maternal antibodies are gradually destroyed in the child’s body. But in response to the penetration of infection, a primary immune response develops in the baby’s body. It is characterized by the fact that it leaves no immunological memory. The next time the child encounters the same microorganism, the child will get sick as the first time. During this period, children are exposed to various kinds viruses that cause ARVI, there is a high incidence of intestinal infections, inflammatory diseases of the respiratory system. Also, childhood infections are severe and atypical if the child has not received maternal antibodies (the mother herself was not sick, was not vaccinated, and did not breastfeed). At the same time, food allergies may develop.
The third critical period is 2-3 years of a child’s life. There is an expansion of contacts with the outside world. At the same time, the primary immune response remains the main one in the functioning of the immune system. The local immune system remains undeveloped; children are especially prone to repeated viral infections and inflammatory diseases respiratory organs.
The fourth critical period is 6-7 years. The levels of immunoglobulins correspond to the parameters in adults, but local immunity of the mucous membranes remains imperfect. At the age of 6-7 years, many chronic diseases develop, and the frequency of allergic diseases increases.
Fifth critical period - adolescence(12-13 years old for girls and 14-15 years old for boys). A period of rapid growth and hormonal changes is combined with a decrease in lymphoid organs that play big role in the system immune defense. After a period of decline, there is a new rise in the incidence of chronic diseases. Severity of atopic diseases ( bronchial asthma etc.) weakens in many children.
Knowledge of the mechanisms of immune development and critical periods in the development of a child’s immune system is extremely important not only for doctors, but also for mothers. This is important for maintaining the health of our children and preventing their development various diseases. And, as you know, prevention is always better than cure.
Let's figure out how the basic mechanisms of immunity are formed. How is it that some people have effective immunity, while others have weak immunity?
The thing is that even before the formation of the fetus, when the egg begins to form and its fertilization occurs, the parental genes are combined, as a result of which genetic information is inherited, which is closely related to the capabilities of the immune system.
It is curious that humans have more than 36,000 genes, and about half of them are in their own way related to the functioning of both the immune system and the entire biological protection body. From this fact we can conclude how important the immune system is.
At some levels of fetal development, various genetic programs are activated, thanks to which central ones are first created, and then peripheral organs immune system. Over time, these organs fill with cells that are created first in the liver and then in the bone marrow. From these cells, after several differentiation operations, cells are formed that form the immune system, primarily lymphocytes, divided into two groups.
The first group is the largest. This is a group of T lymphocytes, which are cells from bone marrow, which move to thymus gland(aka thymus). Since the word "thymus" begins with the letter "t", these cells are called T lymphocytes. In the thymus, which is the main organ of the immune system, lymphocytes undergo a stage of maturation, training and profile change, after which they are transmitted into the blood. Lymphocytes travel through the blood throughout the body and implement the work of immunity at the cellular level.
All lymphocytes that have undergone training in the thymus can react in a special way to any specific irritant agent. The cells are completely ready to defend the “Motherland”, i.e. our body. In other words, these are absolutely mature lymphocytes, but they still have a certain amount of “naivety”, since they have never encountered their real enemy, namely, an agent of infection.
Another group of lymphocytes is smaller, it includes B-lymphocytes (from the first letter of the phrase “bone marrow” - bone marrow). B lymphocytes move from the bone marrow to the spleen and lymph nodes, after which they are constantly on duty throughout the body. Such lymphocytes are also naive guys, since they do not yet have sufficient experience in their work.
The third group of cells heads the immune defense squad and controls the work of both T- and B-lymphocytes. These cells include monocytes and dendritic cells. Such cells have an excellent ability to neutralize various agents through the procedure of phagocytosis. In this case, cells capture foreign agents, are processed with enzymes, cut and destroyed. The resulting processed information is further transmitted to T- and B-lymphocytes. The latter have special receptors on their membrane, with the help of which they recognize a foreign structure (peptide) and act in a special way on these fragmented elements (usually short polypeptides consisting of ten or more amino acids). At the same time, B lymphocytes are activated, moving to special department lymph nodes, as well as special B-dependent zones. Similar zones are present in the spleen.
After contact with macrophages, monocytes or dendritic cells, T lymphocytes are also transferred to the nearest lymph node, but to its own area, which is designated as the T-dependent zone. There, lymphocytes begin to transform into more specialized cells designed to perform specific protective missions.
This is what it looks like initial process, from which the professional, joint work of three types of cells is activated. Upon subsequent interaction with antigens of viruses and bacteria, these special cells increase in size and then divide repeatedly, creating offspring from a single cell, also called a “clone”.
Each clone is specifically designed to combat specific agents: helminths, protozoa, viruses and bacteria. Moreover, agents are selected not only by the type of their structure, but also by individual elements, such as nucleoproteins, proteins, polysaccharides, etc. At this stage, immunity is created. Consequently, immunity is determined by the number of cells of all three types, their ability to instantly respond to foreign agents, recognize them and create antibodies.
An ordinary person has no idea how violent and fascinating processes occur in his body. What is associated with the immune system can be regarded as a confrontation between two programs. Let's study this using the example of an infectious disease.
An infection agent has one program and task. It must penetrate the body and multiply as quickly as possible. The second program, namely, the genetic program of the immune system, is required to quickly respond and use all available protective equipment to combat the multiplying agent. The immune system uses its “soldiers” in the form of T- and B-lymphocytes, which are equipped with special “machine guns” that shoot infection agents with “bullets”, which are special molecules.
If a person's immunity is in perfect order and has a worthy squad of defenders, then soldiers can easily find enemies in any area of the body, be it circulatory system, bronchopulmonary region, urogenital tract or intestines. Lymphocytes will search every corner to detect, destroy and remove strangers from the body. Their main goal is to clear the territory of the enemy, to cleanse the body of gangs of hostile agents. Unfortunately, in most cases, a person is not able to reliably avoid infection, so the body’s entire defense relies on the immune system. The body must be able to stand up for itself.
After the battle is won and the territory is liberated, B- and T-lymphocytes almost die with the honor of the brave, but acquire and store in “memory” for a long time information about the agent of infection and its characteristics. This process is called immunological memory. In the future, if the agent has the courage to return, the memory will help in deploying a defensive response that will be 2-3 times faster and more effective than before. This way, the immune system will fight off the attack again.
This is how the immune system is created and works, striving to create resistance (immunity) of the body to infectious agents various types, promptly identifying and eliminating identified threats to human life. Such information can, of course, be provided by medical centers in Moscow, but isn’t it better to receive it in expanded form, with detailed explanations and illustrations?
Infectious agent – salmonella (group of Escherichia coli):
