Secretory immunoglobulin is normal in saliva. Secretory immunoglobulin a as a factor of local protection of the respiratory tract mucosa and the reasons for its decrease. Immunoglobulin A deficiency increases the risk of developing autoimmune diseases

It is known that the degree of protection against local viral infections of the respiratory and gastrointestinal tract primarily depends on the content of specific secretory IgA in the body, and not on the presence of serum IgG to enteropathogenic or pneumotropic viruses.

Stable structure, pronounced affinity to the surface of the mucous membranes, the predominant content in the secretion of the mammary gland determine the biological role of secretory IgA in protecting the body from the adverse effects of various pathogenic agents, including viruses.

IgA is synthesized in dimeric form in lamina propria cells and after binding to the immunoglobulin receptor synthesized in epithelial cells, it is transported to the surface of the mucous membrane. At the moment of release of IgA into the intestinal lumen, the receptor is partially cleaved, as a result of which a fragment of the receptor remains in the IgA, which is called the secretory component.
Thus, secretory IgA is a product of cooperation of two types of cells - plasma and epithelial.

Secretory IgA is formed not only in dimeric, but also in tetrameric form, which enhances its virus-neutralizing ability. The secretory component protects IgA from being cleaved by proteolytic enzymes, which gives it significant advantages over antibodies of other classes. Secretory IgA neutralizes the virus not only in the intestinal lumen, but also during its transport inside the cell. An IgA dimer can neutralize the virus in the intestinal submucosa, and then, by binding to the receptor, transport it into the intestinal lumen.

Dimeric class A immunoglobulins (US IgA), connected by a j-chain into a single structure with a secretory component, represent a unique example of the evolutionary adaptation of immunoglobulins on mucous membranes for effective functioning under conditions of constant exposure to antigens of various nature.

Based on the ability for local synthesis of molecules secretory componentas well as the dimeric form of IgA-locally located plasma cells, the tissues of the mucous membranes can be divided into three main classes.

In mucous membranes the inductive and productive phases of the humoral immune response are spatially separated to a greater extent than in other parts of the immune system.
Cellular and humoral transformations associated with the emergence of IgA in external secrets are shown in the figure.

Into milk and, apparently, into other external secrets igA molecules come from two main sources. Most of the IgA secreted in saliva, secretions of the lacrimal and mammary glands, as well as the digestive and respiratory tracts, is produced by plasma cells. However, IgA found in various external secrets can also be of systemic origin. Produced by the cells of the mucous membranes of some organs, they enter the bloodstream and are transferred to the mucous membranes of other organs.

After penetration into the Peyer's patch, the antigen activates T- and B-lymphocytes, which along the lymphatic duct enter the mesenteric lymph node, and then into the blood, spleen, again into the blood and are selectively localized in the lymphatic formations of all mucous membranes and exocrine secretory glands - mammary, salivary and lacrimal. In this case, T-lymphocytes are localized mainly between the epithelial cells of the mucous membrane, providing a cellular immune response, and B-lymphocytes - in the lamina propria, where they differentiate into plasma cells and synthesize IgA.
About 90% of plasma cells in the lamina propria produce IgA, while in the lymph nodes the proportion of such cells is only 2-5%.

Unique in this the role of the liver... There is convincing evidence that hepatocytes selectively bind and subsequently transport IgA into bile, thereby enhancing the intestinal secretory IgA system.

Possible liver function also is the removal of antigen-IgA complexes from the circulating blood with bile into the intestine. The study of antiviral immunity has convincingly demonstrated that the degree of protection of the respiratory and gastrointestinal tracts from local viral infections directly correlates with the level of specific secretory IgA, and not with the level of serum antibodies. The antiviral action of secretory IgA is based on the inactivation of the virus.

To protect the mucous membranes, the human body produces immunoglobulin A (IgA). Babies practically do not contact the outside world. Together with the mother's milk, the newborn receives immunoglobulin A, which prevents the multiplication of pathogenic microorganisms on the surface of the nasopharynx.

What is Immunoglobulin A

Immunoglobulin A is found not only in human blood, but also on mucous membranes. Antibodies prevent harmful bacteria from attaching to epithelial cells. The peculiarity of immunoglobulin A is that it is not able to cross the placenta to the fetus. After the baby is born, IgA begins to enter the body along with the mother's colostrum.

Protein compounds are designed to protect the gastrointestinal tract and respiratory tract from pathogenic microorganisms. As they grow older, the baby's immune system begins to form. The baby tastes various objects that can cause infectious diseases. In case of infection, antibodies begin to be produced in the baby's body. After 3 months, the level of IgA in the baby's blood reaches 0.5 g / l.

A blood test for the amount of immunoglobulin A may be required if the following pathologies occur:

The child was diagnosed with a tumor.
The kid suffers from constant allergies.
There is HIV infection in the patient's blood.
The child suffers from chronic diseases of the intestines or liver.
IgA values \u200b\u200bare used to detect Louis-Bar syndrome.
Some children suffer from chronic diarrhea. Doctors need test results to determine the cause of a digestive disorder.
Immunoglobulin A levels vary in children with malabsorption syndrome.

In these diseases, mucous membranes are affected, which must be protected by immunoglobulin A.

Important! The immune defense of the newborn is quite dependent on breast milk. Babies who are fed artificial mixtures are much more likely to suffer from infectious diseases.

Features of preparation for the test

To make a more accurate diagnosis, the doctor prescribes a referral to check the IgA level. Experts recommend that patients give up tea and coffee before the procedure. The examination must be done on an empty stomach, as food affects the composition of the blood. Use plain water to quench your thirst, not juice or soda. Immunoglobulin levels change with exercise. Children should not be nervous before the procedure, since emotional experiences affect the production of protein compounds. When examining adolescents, doctors pay attention to ESR indicators. Indicators of the rate of erythrocyte sedimentation affect the condition of the mucous membranes and skin. A decrease in the amount of IgA reduces the body's defenses. Due to frequent illnesses, the student is forced to miss classes.

The amount of immunoglobulin A in healthy children

The number of defense cells produced by the immune system depends on the age of the child. Babies up to 3 months receive IgA along with their mother's milk. A newborn has practically no synthesis of its own antibodies.

In the blood of children from 1 to 4 years old, the amount of IgA should be in the range from 0.2 to 1.0 g / l. In children from 4 to 7 years old, the content of immunoglobulin A reaches 1.95 g / l. The amount of antibodies in the plasma of schoolchildren aged 7 to 10 increases to 3.05 g / l.

Important! The norm of immunoglobulin A in children should be appropriate for their age.

Why is the child producing too much IgA?

An excess of immunoglobulin A in the baby's blood can occur for several reasons:

Abnormal IgA levels may be associated with the development of bacterial infections that affect the baby's respiratory tract, stomach or intestines.
Immunoglobulin A is elevated in a child if pathological processes occur in the liver.
Exceeding the indicators is detected in patients who suffer from leukemia.
The body produces too many antibodies to kill measles or rubella pathogens.

Factors that lead to a decrease in immunoglobulin A

Constant colds in children cause concern among parents. After examination, doctors identify deviations from the norm in the IgA indicator. They have a question about what a lowered immunoglobulin means in a child?

There are several reasons that lead to a deficiency of immunoglobulin A:

IgA production is reduced due to inflammation of the colon lining. Immunoglobulin A is lowered in a child due to nephrotic syndrome.
The reason for the drop in IgA levels can be tumors that form in the lymphatic system.
Immunodeficiency states pose a danger to the baby. Low immunoglobulin indicates thymic hypoplasia.
The body's defenses are reduced in children who have received extensive burns.
The production of protective cells is impaired in renal failure.

General information about the study

Class A immunoglobulins are glycoproteins that are synthesized mainly by plasma cells of the mucous membranes in response to local exposure to the antigen.

In the human body, IgA exists in two forms - serum and secretory. Their half-life is 6-7 days. Secretory IgA has a dimeric structure and is resistant to enzymes due to its structural features. Secretory IgA is found in tears, sweat, saliva, milk and colostrum, bronchial and gastrointestinal secretions, and protects mucous membranes from infectious agents. 80-90% of IgA circulating in the blood consists of the serum monomeric form of this class of antibodies. IgA are included in the fraction of gamma globulins and make up 10-15% of all blood immunoglobulins.

IgA antibodies are an important factor in the local protection of the mucous membranes. They bind to microorganisms and prevent their penetration from the outer surfaces into the tissues, enhance phagocytosis of antigens by activating complement along an alternative path. A sufficient level of IgA in the body prevents the development of IgE-dependent allergic reactions. IgA does not cross the placenta, but enters the baby's body through the mother's milk during feeding.

Selective IgA deficiency is one of the most common immunodeficiencies in the population. The frequency is 1 case per 400-700 people. This pathology is often asymptomatic. IgA deficiency can manifest itself as allergic diseases, recurrent respiratory or gastrointestinal infections, and is often associated with autoimmune pathology (diabetes mellitus, systemic lupus erythematosus, rheumatoid arthritis, pernicious anemia). IgA deficiency is sometimes combined with insufficient levels of IgG-2 and IgG-4, which leads to more pronounced clinical signs of immunodeficiency.

When is the study scheduled?

When examining children and adults prone to frequent recurrent respiratory, intestinal and / or urogenital infections.
When monitoring treatment for IgA-type myeloma.
When examining patients with systemic connective tissue diseases (autoimmune pathology).
With a comprehensive study of the state of the immune system.
With neoplasms of hematopoietic and lymphoid tissues.
When monitoring patients with immunodeficiency.

There are times when patients are given a referral for analysis, the meaning of which they often do not know. For example, what are class A immunoglobulins? A referral for the analysis of IgA immunoglobulin can come from a doctor for both children and adults. So what can this indicator tell the doctor about?

What is immunoglobulin A?

Immunoglobulin A is a clear indicator of the state of humoral immunity. This protein can be contained in the body in serum and secretory fractions (both in the blood and in the secretions of the glands). The serum fraction provides local immunity and is produced in increased amounts in response to inflammatory processes. The secretory fraction is contained in the secrets of the body - saliva, breast milk, secretory fluid in the intestines or bronchi, in tears.

The function of immunoglobulin A is to bind to harmful microorganisms and thereby prevent cell damage. A certain amount of IgA is constantly present in the blood and glandular secretions. A decrease in immunoglobulin A means a deficiency in the immune system. An increase in immunoglobulin A is observed either with sensitization of the immune system due to systemic diseases, or (which is most often) with inflammatory processes.

After it became clear what it is - immunoglobulin A, the next question arises - for what purpose is it being tested? The usual indications for such an analysis is a comprehensive examination for frequent infectious diseases - for example, when children often suffer from colds or intestinal infections. In this case, the child's immunoglobulin A will either be reduced, which is an indicator of immunodeficiency, or will be normal, and then the cause must be looked for in other factors, or increased, which will demonstrate the current acute inflammatory process.

In other cases, the analysis for class A immunoglobulin is carried out when immunodeficiency is suspected and when monitoring the condition of patients with diagnosed immunodeficiencies, when neoplasms are detected, when diagnosing autoimmune pathologies, and to check the effectiveness of treatment for myeloma.

Thus, IgA is responsible for the parameters of immunity and is necessary for diagnosing the causes of various recurrent diseases, as well as for controlling the immune system in various systemic diseases.

How is blood taken for analysis?

For the immunoglobulin A test, venous blood must be drawn. Since antibodies are a very specific structure that differs from the main biochemical elements of blood, the rules for preparing for analysis for them differ from the usual ones. For example, there is no restriction on food intake for 8-12 hours. It is impossible to eat before the analysis for immunoglobulin within 3 hours. You can drink non-carbonated clean water.

Half an hour before the analysis, one should not be very nervous and be physically strenuous. Therefore, if a child donates blood, the task of the parents is to ensure that he behaves calmly and does not worry about donating blood within the specified time frame. It should be explained in a calm voice that the procedure is carried out quickly and painlessly, to distract the child to some activity.

It is undesirable to drink alcohol a day before the analysis. Smoking should be stopped at least 3 hours before the procedure. Due to the fact that immunoglobulin A is produced, among other things, as an immune response to irritation of the bronchi, smoking (including vaping) can negatively affect the test results.

What factors can further distort the result?

In addition to the above, there are some other factors that can affect the result. They should be taken into account by the attending physician, who will evaluate the result of the analysis. These factors include, first of all, pregnancy, in which there is usually a low immunoglobulin level... In addition, extensive burns, renal failure, drugs that lower immunity and various types of radiation can reduce the IgA concentration.

Among the factors that increase the content of immunoglobulin A, some medications (mainly antipsychotics, anticonvulsants, antidepressants and oral contraceptives), vaccinations given less than 6 months ago, as well as excessive physical, mental and emotional stress immediately before donating blood.

In some cases, the deficiency of immunoglobulin A is associated with a specific feature of the patient's body - it produces antibodies against its own IgA protein. These patients are at high risk of developing autoimmune diseases and infections. In addition, there is a risk of developing an anaphylactic reaction with blood transfusion or organ donation.

Immunoglobulin A content standards

Due to the fact that from birth our immune system is imperfect, in babies for some time, their own IgA is not produced by the body, but comes with the mother's milk (this is one of the reasons why breast-feeding so important in the early stages). The norm of immunoglobulin A in children under one year old is 0.83 g / l.

As can be seen from the standards, an adult has not only the highest upper limit of the permissible norm, but also the greatest variability of indicators. They can be associated both with the individual characteristics of the organism, and with the action of any stimuli and vary slightly even within one day.

If immunoglobulin A is elevated

If the content of immunoglobulin A is outside the upper limit, i.e. immunoglobulin A is elevated - what does this mean? Many diseases can increase IgA levels. Among the main causes are infections that affect the skin, bronchi, lungs, intestines, genitals and urinary organs. In addition, various neoplasms, including malignant ones, are a common cause of an increase in immunoglobulin A.

A high concentration of IgA can be shown in cystic fibrosis, liver disease, systemic autoimmune diseases. The lifespan of immunoglobulins of this class is approximately 6-7 days, and the detection of an increased concentration of IgA in the blood means that the inflammatory process either exists in the body at the time of analysis, or was present not earlier than a week ago. If the parameters of the analysis are borderline, then a repeated sample is carried out in a week, excluding the possible factors of distortion of the results.

If immunoglobulin A is low

Immunoglobulin A is lowered if the body's immune system has malfunctioned and does not produce enough proteins to defend itself. This situation develops with HIV, removal of the spleen,. Other diseases that can cause a decrease in IgA - chronic diseases respiratory system, colon, kidneys. In addition, the decrease in immunoglobulin A can be explained by innate characteristics of the body, which were already mentioned earlier in the text.

Selective immunodeficiency of immunoglobulin A is more common among the population than other types of immunodeficiency. By itself, it is often asymptomatic, leaving only indirect hints in the form of often recurrent infectious diseases or allergic reactions. The disease can sharply declare itself in a situation of stress for the body - a change in climatic conditions, a diet, during pregnancy and childbirth, hormonal failure, severe emotional stress.

Patients whose immunoglobulin A content is insufficient may experience various allergic reactions or develop asthma. The most common symptoms experienced by a person with selective immunoglobulin A deficiency are anaphylactic shock upon contact with previously harmless irritants, increased sensitivity of the respiratory system, and urinary dysfunction. Less common are intestinal disorders, inflammation of the conjunctiva of the eye, and diseases of the lungs and bronchi.

The exact cause of selective deficiency of immunoglobulin A is unknown. Various hypotheses have been put forward, including congenital traits (inherited or by accidental mutation), prolonged stress, poor social conditions (in particular, malnutrition), poisoning with hazardous substances, and cancer.

Evaluation of the results

A blood test for the content of immunoglobulin A takes on average 2-3 days from the date of the test. The research is inexpensive, within 200 rubles (prices may vary depending on the specific laboratory). For an adequate and complete picture of the patient's condition, in addition to the analysis for immunoglobulin A, tests are also performed for other immunoglobulins: E, G, M.

In addition to finding out the content of immunoglobulins, for a complete picture of the state of the immune system, the patient must pass tests for the general blood count, leukocyte count, ESR, and protein fractions in serum. If the attending physician has reason to suspect a specific disease, then at his discretion other, additional tests are prescribed. In other words, the analysis for the IgA content itself is not very informative, it is valuable only if it is included in a full examination.

What is immunoglobulin A?

After it became clear what it is - immunoglobulin A, the next question arises - for what purpose is it being tested? The usual indications for such an analysis is a comprehensive examination for frequent infectious diseases - for example, when children often suffer from colds or intestinal infections. In this case, the child's immunoglobulin A will either be reduced, which is an indicator of immunodeficiency, or it will be normal, and then the cause must be sought in other factors, or increased, which will demonstrate the current acute inflammatory process.

How is blood taken for analysis?

What factors can further distort the result?

Among the factors that increase the level of immunoglobulin A, some drugs should be noted (mainly antipsychotics, anticonvulsants, antidepressants and oral contraceptives), vaccinations given less than 6 months ago, as well as excessive physical, mental and emotional stress immediately before donating blood.

Immunoglobulin A content standards

Due to the fact that from birth our immune system is imperfect, in babies for some time their own IgA is not produced by the body, but comes from the mother's milk (this is one of the reasons why breastfeeding is so important in the early stages). The norm of immunoglobulin A in children under one year old is 0.83 g / l.

If immunoglobulin A is elevated

If immunoglobulin A is low

Immunoglobulin A is lowered if the body's immune system has malfunctioned and does not produce enough proteins to defend itself. This situation develops with HIV, removal of the spleen,. Other diseases that can cause a decrease in IgA are chronic diseases of the respiratory system, colon, kidneys. In addition, the decrease in immunoglobulin A can be explained by innate characteristics of the body, which were already mentioned earlier in the text.