Immunoglobulins A, D, E, G, M. The importance of tests for IgG, IgM, IgA antibodies in the diagnosis of infections Why is iga increased in saliva

It is known that the degree of protection against local viral infections respiratory and gastrointestinal tracts 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 for the surface of the mucous membranes, the predominant content in the secretion of the mammary gland determines biological role 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. When IgA enters the intestinal lumen, the receptor is partially cleaved, leaving a fragment of the receptor in the IgA, which is called the secretory component.
Thus, secretory IgA is a product of cooperation between 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 cleavage by proteolytic enzymes, which determines its significant advantages over antibodies of other classes. Secretory IgA neutralizes the virus not only in the intestinal lumen, but also during its transport into the cell. The IgA dimer can neutralize the virus in the intestinal submucosa and then, by binding to the receptor, transport it into the intestinal lumen.

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

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

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

In milk and, apparently, in other external secretions 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 formed by plasma cells. However, IgA, found in various external secretions, can also be of systemic origin. Produced by the cells of the mucous membranes of some organs, they enter the blood and are transferred to the mucous membranes of other organs.

The antigen, after penetration into the Peyer's patch, 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 lymphatic formations all mucous membranes and exocrine secretory glands - mammary, salivary and lacrimal. In this case, T lymphocytes are localized predominantly between the epithelial cells of the mucous membrane, providing a cellular immune response, and B lymphocytes are located in the lamina propria, where they differentiate into plasma cells and synthesize IgA.
About 90% of plasma cells are in the lamina propria produce IgA, while in lymph nodes the proportion of such cells is only 2-5%.

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

Possible liver function is also the removal of antigen-IgA complexes from the circulating blood with bile into the intestines. Studying antiviral immunity 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 effect of secretory IgA is based on virus inactivation.

Immunoglobulin A (IgA)

(information for specialists)

Immunoglobulins A are glycoproteins produced by plasma cells of the mucous membranes in response to the introduction of an antigen. They belong to γ-globulins and constitute up to 10-15% of all blood immunoglobulins.

IgA is a factor of local defense of the body. The essence of the protection mechanism is as follows: IgA binds the antigen that has reached the mucous membranes and prevents its further penetration into the body. In addition, these immunoglobulins trigger the complement system along the alternative pathway and enhance phagocytosis. Another function of IgA is to prevent the development of IgE-dependent allergic reactions.

IgA does not penetrate the placenta, but can be transmitted from mother to child through breastfeeding.

IgA in the human body exists in two forms: secretory and serum. Secretory IgA is found in tears, sweat, saliva, milk, colostrum, bronchial secretions and gastrointestinal tract. Its main function is protection against infectious diseases. The serum form accounts for up to 80-90% of IgA circulating in the blood.

Among all the immunodeficiencies that develop in humans, selective IgA deficiency is the most common. Clinically, this condition often does not manifest itself. However, in some cases people develop allergic reactions, recurrent respiratory, gastrointestinal and urogenital infections, as well as autoimmune diseases.

A decrease in IgA levels can be congenital or acquired. In the case of congenital deficiency of immunoglobulin A, the likelihood of the patient developing autoimmune processes and the production of antibodies to IgA increases. The presence of antibodies to IgA in the blood during transfusion of blood components or intravenous administration immunoglobulins can lead to an anaphylactic reaction.

Indications for the study:

Children and adults suffering frequent relapses respiratory, intestinal and/or urogenital infections.

Patients who have systemic diseases connective tissue(autoimmune pathology).

A comprehensive study of the state of the immune system.

Monitoring the effectiveness of therapy for IgA-type myeloma.

Monitoring of patients with immunodeficiencies.

For neoplasms of hematopoietic and lymphoid tissues.

Material for research: venous blood

Preparing the patient for the study:

Avoid meals 2-3 hours before the test; you can drink clean still water.

Avoid smoking 3 hours before the test.

30 minutes before the test, avoid physical and emotional stress.

Reference values:

The total concentration of IgA in blood serum is normally 0.7-4 g/l.

Interpretation of results:

Reasons for decreased IgA levels

Reasons for increased IgA levels

Hereditary IgA deficiency (selective).

Common variable immunodeficiency.

Neoplasms (carcinomas, endotheliomas).

Leukemia.

Systemic connective tissue diseases ( rheumatoid arthritis, vasculitis, systemic lupus erythematosus).

Celiac disease.

Multiple myeloma (significant increase in IgA).

Splenectomy.

Chronic liver pathology (cirrhosis, alcoholic illness liver, portal cirrhosis).

AIDS.

Mediterranean lymphoma of the small intestine.

Chronic candidiasis of the skin and mucous membranes.

Scheinlein-Henoch disease (hemorrhagic vasculitis).

Physiological hypo-γ-globulinemia in children aged 3-6 months.

Chronic lymphocytic leukemia.

α-γ-globulinemia.

Lymphomas.

Hypo-γ-globulinemia.

Cystic fibrosis.

Hyper-IgM syndrome.

Waldenström's disease.

Ataxia-telangiectasia (hereditary and acquired).

Monoclonal gammopathy.

Giardiasis.

Wiskott-Aldrich syndrome.

Chronic diseases of the respiratory system.

Inflammatory diseases of the colon.

Nephrotic syndrome.

Possible influences on the result of the study:

Factors that reduce IgA levels

Factors that increase IgA levels

Pregnancy.

Intense physical exercise.

nephrotic syndrome, renal failure accompanied by protein loss.

Immunization in the previous 6 months.

Burns.

Reception series medicines(carbamazepine, chlorpromazine, dextran, estrogens, gold preparations, methylprednisolone, oral contraceptives, penicillamine, valproic acid).

Enteropathies accompanied by protein loss.

Taking cytostatics and immunosuppressants.

Radiation therapy, irradiation.

Immunoglobulin A is an indicator of humoral immunity. It is determined for evaluation local immunity, acute infectious processes, diseases of the kidneys, liver, chronic inflammation. At the Yusupov Hospital, laboratory technicians use high-quality reagents to determine the level of immunoglobulins A. Research results are interpreted by professors and doctors highest category. Immunologists carry out therapy aimed at normalizing the concentration of immunoglobulins A. Therapists use effective drugs, registered in the Russian Federation, with minimal side effects.

Immunoglobulins A are proteins that provide local immunity. They are presented in the human body in two fractions: serum, which provides local immunity, and secretory. The secretory fraction is contained in milk, respiratory and intestinal secretions, tear fluid and saliva, which protect together with nonspecific factors immunity protection of mucous membranes from viruses and bacteria.

Functions of immunoglobulin A

Serum immunoglobulin A is a fraction of gamma globulins. It makes up 10-15% of the total amount of all soluble immunoglobulins. In blood serum, immunoglobulin A is represented mainly by monomeric molecules. The main amount of immunoglobulin A is not found in the blood serum, but on the surface of the mucous membranes. Secretory immunoglobulin facilitates the transport of immunoglobulin A across the epithelium. It protects immunoglobulin molecules from breakdown by digestive tract enzymes.

Main function serum immunoglobulin A – ensuring local immunity, protection of the genitourinary, respiratory tract and digestive organs from pathogens of infectious diseases. Secretory antibodies have a pronounced anti-adsorption effect: they prevent the attachment of bacteria to the surface of epithelial cells, prevent the adhesion of microorganisms, without which bacterial damage to the cell becomes impossible. Also, immunoglobulins A, together with nonspecific immune factors, provide protection of mucous membranes from microorganisms. Congenital or acquired deficiency of immunoglobulin IgA can lead to allergies, autoimmune disorders, allergies, and repeated infections.

Immunoglobulin A does not cross the placental barrier. Its level in newborns is about 1% of the concentration in adults. By the first year of a child’s life, this figure is 20% of the adult level. After the baby is born, secretory immunoglobulins enter his body with the mother's colostrum. They protect the child’s gastrointestinal tract and respiratory tract. The age of 3 months is critical. During this period, doctors diagnose congenital or transient deficiency of local immunity. By the age of five, the level of immunoglobulin A reaches the concentration characteristic of an adult.

The level of immunoglobulin A in children depends on their age. In children from 3 to 12 months it is 0.02-0.05 g/l, from 12 to 16 years it is in the range of 0.6-3.48 g/l. In adults over 20 years of age, normal level immunoglobulin A varies from 0.9 to 4.5 g/l.

Indications for immunoglobulin A testing

With the help of immunoglobulins A, doctors assess the course of diseases that occur with activation of the immune system:

Immunoglobulin IgA is determined if there is the following diseases:

  • recurrent bacterial respiratory infections(sinusitis, pneumonia), as well as otitis and meningitis, bronchial asthma;
  • chronic diarrhea, malabsorption syndrome;
  • anaphylactic post-transfusion reactions;
  • Louis-Bar syndrome (ataxia - telangiectasia);
  • tumor diseases lymphoid system (myeloma, leukemia, reticulosarcoma, lymphoma).
  • chronic hepatitis, liver cirrhosis.

Using IgA immunoglobulin testing, doctors at the Yusupov Hospital check the functioning of the liver, stomach, intestines, and lymphatic system.

Collection of biomaterial for research

In order to determine the level of immunoglobulin A, a sample is taken venous blood into an empty test tube or with gel (to obtain serum). Patients with low level immunoglobulins on the eve of the study, preventive measures should be taken bacterial infection. The venipuncture site is pressed with a cotton ball until the bleeding stops. If a hematoma has formed at the site of the vein puncture. Apply a warm compress.

The patient is advised to refrain from eating for 12-14 hours before the test. He can drink pure still water. Doctors stop medications that may affect the results of the study. 3 days before taking blood, the patient must stop drinking alcohol. Analysis results can be obtained within 4 hours.

Reasons for increased immunoglobulin A in adults

Immunoglobulins A bind to microorganisms and delay their attachment to the cell surface. A decrease in the content of immunoglobulins A indicates a deficiency of local and general immunity. Their concentration increases in the following diseases:

The level of immunoglobulin A decreases in patients suffering from diseases that deplete the immune system. Immunoglobulin A may be low in a child with an acute viral infection

Decreased immunoglobulin A levels

Immunoglobulin A is reduced in patients with neoplasms of the lymphatic system, lymphoproliferative diseases, pernicious anemia, and hemoglobinopathies. The content of immunoglobulin A decreases after splenectomy, in case of protein loss due to enteropathies and nephropathies. Treatment with immunosuppressants, cytostatics, and exposure to ionizing radiation can also reduce the level of immunoglobulin IgA.

Long-term exposure to benzene, toluene, xylene can lower the level of immunoglobulin A, taking medicines: dextran, estrogens, methylprednisolone, carbamazepine, gold preparations, valproic acid. Get a consultation with an immunologist by making an appointment by calling the Yusupov Hospital. The doctor will conduct an examination and prescribe a test for immunoglobulin A levels.

Synonyms: immunoglobulins class A, IgA. Immunoglobulin A

Scientific editor: M. Merkusheva, PSPbSMU named after. acad. Pavlova, medical practice.
September, 2018.

Basic information

Immunoglobulins (IG) are glycoproteins or protein compounds of blood plasma (antibodies), which in the human body are synthesized by cells of the immune system (B-lymphocytes) in response to the damaging effects of various antigens: viruses, microbes, bacteria, protein toxins, etc. Associated with pathogenic microorganisms, antibodies block their reproduction and neutralize them toxic effect. Thus, immunoglobulins provide immune protection of the body at the local level (humoral immunity).

The mass fraction of class A immunoglobulins is 15-20% of all soluble glycoproteins. There are 2 types of IgA: serum and secretory. At the same time most IgA is not found in blood serum, but on the surface of mucous membranes, in milk and colostrum, secretions of the gastrointestinal tract (GIT) and bronchi, tears, saliva, bile and urine.

The main function of serum IgA is to protect the gastrointestinal tract, genitourinary and respiratory tract from the damaging effects of viruses. Secretory immunoglobulins And prevent attachment pathogenic microorganisms to the surface of epithelial cells and block adhesion (the formation of connections between cells), which ultimately makes it impossible to damage them and prevent bacteria and viruses from penetrating under the cell membrane.

Indications for analysis

Doctors prescribe an immunoglobulin A (IgA) test to assess the severity of diseases in which local immunity is involved:

The results of the IgA examination make it possible to establish the form and stage of the disease, as well as to develop the most effective treatment tactics.

Norms

Please note that the information below cannot be used for self-diagnosis and self-medication. The interpretation of the results is carried out only by the attending physician, taking into account the data from the patient’s survey/examination, anamnesis/medical history, additional laboratory and/or instrumental studies etc.

Important! Standards vary depending on the reagents and equipment used in each particular laboratory. Therefore, when interpreting the results, it is necessary to use the standards adopted in the laboratory where the analysis was carried out.

Below are options for reference values.

Data from the reference book, ed. Doctor of Medical Sciences, Prof. A.A. Kishkuna:

A number of factors may influence the results obtained:

  • psychological stress or physical activity;
  • reception alcoholic drinks or drugs, smoking;
  • receiving radiation or chemotherapy (reduces concentration);
  • taking certain medications:
    • anticonvulsants;
    • hydantoin derivatives;
    • oral contraceptives;
    • steroids;
    • hormones;
    • enzymes;
    • analgesics;
    • cytostatics, etc.
  • previous BCG vaccination(reduces the level of immunoglobulins).

Important! The interpretation of the results is always carried out comprehensively. Put accurate diagnosis based on only one analysis is impossible.

IgA increased

An increase in IgA most often indicates the likelihood of developing the following pathologies:

  • Purulent infections of the gastrointestinal tract and respiratory tract, mainly in a chronic form;
  • Alcoholism (long-term binge drinking);
  • Liver diseases (cirrhosis, oncology, hepatitis, etc.);
  • Autoimmune diseases (lupus, rheumatoid arthritis, etc.);
  • Wiskott-Aldrich syndrome (immunodeficiency and inhibition of platelet production);
  • Oncology (multiple myeloma, etc.);
  • Cystic fibrosis (damage to organs that produce mucus);
  • Enteropathies (non-inflammatory bowel diseases in chronic form);
  • Asymptomatic monoclonal IgA gammopathy.

IgA nephropathy is characterized by increased level IgA in the blood serum and its deposition in the renal glomeruli. Research has shown that people's tonsils are IgA nephropathy produce IgA in increased quantity.

IgA is reduced

A decrease in the level of acquired IgA is observed in diseases:

  • physiological hypogammaglobulinemia in children aged 3-6 months;
  • oncological diseases lymphatic system;
  • recent splenectomy (removal of the spleen);
  • loss of proteins during enteropathies and nephropathies (damage to the glomeruli and renal parenchyma);
  • hemoglobinopathy (disorder of hemoglobin structure);
  • pernicious anemia(B-12 is in short supply);
  • treating the patient with cytostatics, immunosuppressants, etc.;
  • atopic dermatitis (allergic rashes);
  • exposure of the patient to ionizing radiation.

Congenital deficiency:

  • Bruton's disease (immunodeficiency caused by a gene mutation);
  • insufficiency of humoral immunity;
  • selective IgA deficiency;
  • Louis-Bar syndrome;

This test can be prescribed and interpreted by an immunologist, oncologist, nephrologist, infectious disease specialist or general practitioner.

Preparation

The biomaterial for research is venous blood.

  • Blood sampling is carried out in the morning (before 12.00) and strictly on an empty stomach. The last meal should be taken 8-10 hours before the test. In the morning before the procedure, you are allowed to drink plain water without gas;
  • Smoking is prohibited 2-3 hours before the procedure, incl. electronic cigarettes, and use nicotine substitutes (patch, spray, chewing gum, pills);
  • The day before and 40 minutes before the analysis, you should observe a rest regime. The patient is prohibited from worrying, running, lifting weights, etc.;
  • The attending physician must be notified in advance about taking any medications. It is possible that some of them will have to be canceled at the time of the study.

Important! Before the study, patients with previously diagnosed low levels of IgA should be prevented from bacterial and viral diseases.

Patients with elevated IgA and symptoms of monoclonal gammopathy (increased secretion of plasma cells) should alert their physician to the presence of symptoms (bone tenderness, aching sensation, muscle weakness). Plasma cells inhibit hematopoiesis, which may affect test results.

You should know that Blood sampling is not carried out in the following cases:

You should also take into account that the use of alcohol, drugs, energy drinks and other tonic drinks or drugs can distort the results obtained.

In the Lab4U online laboratory, we want each of you to be able to take care of your health. To do this, we simply and clearly talk about the body’s indicators.

In the online laboratory Lab4U, serological tests are performed to detect pathogen antigens and specific antibodies to them - this is the most exact method diagnosis of infectious diseases. “Why is it necessary to take an antibody test to diagnose infections?” This question may arise after a doctor has sent you to the laboratory. Let's try to answer it.

Content

What are antibodies? And how to decipher the results of the analysis?

Antibodies are proteins that immune system produced in response to infection. IN laboratory diagnostics It is antibodies that serve as a marker of infection. General rule The preparation for an antibody test is to donate blood from a vein on an empty stomach (at least four hours must pass after eating). In a modern laboratory, blood serum is examined on an automatic analyzer using appropriate reagents. Sometimes a serological test for antibodies is the only way to diagnose infectious diseases.

Tests for infections can be qualitative (they answer whether there is an infection in the blood) or quantitative (they show the level of antibodies in the blood). The level of antibodies for each infection is different (for some there should be none at all). Reference values ​​(normal values) of antibodies can be obtained with the test result.
In the online laboratory Lab4U you can take it in one go and

Various classes of antibodies IgG, IgM, IgA

Enzyme immunoassay determines infection antibodies belonging to different Ig classes (G, A, M). Antibodies to the virus, in the presence of infection, are determined very early stage, which provides effective diagnostics and disease control. The most common methods for diagnosing infections are tests for IgM antibodies ( acute phase course of infection) and IgG antibodies (stable immunity to infection). These antibodies are detected for most infections.

However, one of the most common tests does not differentiate the type of antibodies, since the presence of antibodies to the viruses of these infections automatically assumes chronic course diseases and is a contraindication, for example, for serious surgical interventions. Therefore, it is important to refute or confirm the diagnosis.

A detailed diagnosis of the type and amount of antibodies in a diagnosed disease can be done by taking an analysis for each specific infection and type of antibodies. Primary infection is detected when detected diagnostically significant level IgM antibodies in a blood sample or a significant increase in the number of IgA or IgG antibodies in paired sera taken 1-4 weeks apart.

Reinfection, or repeated infection, is detected by a rapid rise in the level of IgA or IgG antibodies. IgA antibodies have higher concentrations in older patients and are more accurate in diagnosing ongoing infection in adults.

A past infection in the blood is defined as elevated IgG antibodies without an increase in their concentration in paired samples taken with an interval of 2 weeks. In this case, there are no antibodies of classes IgM and A.

IgM antibodies

Their concentration increases soon after illness. IgM antibodies are detected as early as 5 days after its onset and reach a peak between one and four weeks, then decrease to diagnostic levels. minor levels for several months even without treatment. However, for full diagnostics It is not enough to determine only class M antibodies: the absence of this class of antibodies does not mean the absence of the disease. There is no acute form of the disease, but it may be chronic.

IgM antibodies have great value in the diagnosis of easily transmitted childhood infections (rubella, whooping cough, chickenpox) by airborne droplets, since it is important to identify the disease as early as possible and isolate the sick person.

IgG antibodies

The main role of IgG antibodies is the long-term protection of the body from most bacteria and viruses - although their production occurs more slowly, the response to an antigenic stimulus remains more stable than that of IgM class antibodies.

Levels of IgG antibodies rise more slowly (15-20 days after the onset of illness) than IgM antibodies, but remain elevated longer, so they may indicate a long-standing infection in the absence of IgM antibodies. IgG may remain at low levels for many years, but upon repeated exposure to the same antigen, IgG antibody levels rise rapidly.

For a complete diagnostic picture, it is necessary to determine IgA and IgG antibodies simultaneously. If the IgA result is unclear, confirmation is carried out by determining IgM. In case positive result and for accurate diagnosis a second test, done 8-14 days after the first, should be checked in parallel to determine the increase in IgG concentration. The results of the analysis must be interpreted in conjunction with information obtained in other diagnostic procedures.

IgG antibodies, in particular, are used for diagnosis - one of the causes of ulcers and gastritis.

IgA antibodies

They appear in serum 10-14 days after the onset of the disease, and at first they can even be detected in seminal and vaginal fluids. The level of IgA antibodies usually decreases by 2-4 months after infection in the case of successful treatment. With repeated infection, the level of IgA antibodies increases again. If the IgA level does not fall after treatment, then this is a sign chronic form infections.

Antibody analysis in the diagnosis of TORCH infections

The abbreviation TORCH appeared in the 70s of the last century, and consists of capital letters Latin names groups of infections distinctive feature which is that while it is relatively safe for children and adults, TORCH infections pose an extreme danger during pregnancy.

Often, infection of a woman with TORCH complex infections during pregnancy (the presence of only IgM antibodies in the blood) is an indication for termination.

In conclusion

Sometimes, having discovered IgG antibodies in the test results, for example, toxoplasmosis or herpes, patients panic without looking at the fact that IgM antibodies, which indicate the presence of a current infection, may be absent altogether. In this case, the analysis indicates a previous infection to which immunity has developed.

In any case, it is better to entrust the interpretation of the test results to a doctor, and, if necessary, decide on treatment tactics with him. And you can trust us to take the tests.

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