IgG – norms, interpretation, role in the body [EXPLAINED]

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IgG are important antibodies in our body. They are the most durable and effectively protect our body against various diseases and infections. Importantly, on the basis of their concentration, we can diagnose serious diseases such as myeloma. These antibodies are passed on by the mother to the baby even before it is born. What are IgG antibodies? What is an IgG test? What are the below- or above-normal results?

An immunoglobulin test measures the level of types of antibodies in the blood. The immune system produces antibodies to protect the body against bacteria, viruses, fungi and allergens.

The body makes various antibodies or immunoglobulins to fight infection and disease. For example, an anti-chickenpox antibody is not the same as an anti-mononucleosis antibody. Sometimes the body can mistakenly make antibodies against itself, treating healthy organs and tissues as a potential danger – this is autoimmune disease (autoimmune disease).

Also read: Is there an autoimmune disease and what are its types?

Types of Ig antibodies

The following types of antibodies (immunoglobins) are distinguished:

  1. immunoglobulin A (IgA): found in the mucous membranes of the respiratory tract and digestive system, as well as in saliva (sputum), tears and breast milk
  2. immunoglobulin G (IgG): found in the blood and other body fluids, protects against bacterial and viral infections,
  3. immunoglobulin M (IgM): found mainly in the blood and lymph fluid. It is the first antibody produced by the body when it is fighting a new infection.
  4. immunoglobulin E (IgE): usually found in small amounts in the blood. This amount may increase when the body overreacts to allergens or fights a parasitic infection,
  5. immunoglobulin D (IgD): this is the least studied type of immunoglobulin. It makes up less than 1% of the immunoglobulins in the blood.

Your doctor may want to do an immunoglobulin test to check if whether the person is infected or protected against (resistant to) infection. Doctors also use immunoglobulin tests to diagnose immunodeficiency (when the immune system is not working as it should) and when they suspect an immunodeficiency in a child who has numerous infections in a short time.

Tests can also be done as part of assessing allergies or autoimmune conditions such as juvenile idiopathic arthritis, lupus, and celiac disease.

IgG testing is also of great importance during the coronavirus pandemic. The POLMED company has introduced a test for the presence of antibodies against the SARS-CoV-2 coronavirus to its offer. This test does not detect the presence of the virus itself, but the presence of IgG and IgM antibodies, which may suggest ongoing or past COVID-19 infections.

Also read: How to build immunity in a child?

IgG is also known as G-type antibodies. These are immune proteins produced by cells of the immune system, i.e. plasma cells. IgG is produced when in contact with various antigens that are treated by our immune system as foreign.

Antigens are fragments of viruses, bacteria, fungi, foods, and sometimes even the body’s own tissue. The actions of IgG are specific and always directed against a specific antigen and are produced in the immune response to replace the less specific IgM antibodies.

See: What are antigens and what is their role in the body?

Our body produces IgG as the last one, and thanks to the immunological memory of plasma cells, they can remain in the blood for several dozen years. Therefore, they are considered the most persistent antibodies.

IgG can form entire immune complexes with antigen molecules and activate the complement system, i.e. groups of proteins that initiate inflammation. This is to neutralize the antigen so that it can be safely removed from the body.

IgG antibodies cross the placenta, therefore the pregnant woman passes all her antibodies to the fetus. They will persist in your baby’s body for about a year after giving birth. In addition, the baby will also produce its antibodies upon contact with antigens after birth.

IgG immunoglobulins are divided into four groups due to differences in structure:

  1. IgG1 – these are the most numerous IgG, accounting for 67 percent. of all subtypes, IgG1 deficiency usually occurs during a general antibody deficiency,
  2. IgG2 – that’s 22 percent. IgG and has the lowest specificity, the symptom of their deficiency are recurrent bacterial and viral infections,
  3. IgG3 – account for 8 percent. IgG and activate the complement system the most, their deficiency is manifested by viral infections,
  4. IgG4 – the smallest subtype of IgG, which accounts for only 3%, protects the body against allergic reactions and is the only one that does not activate the complement system, the increase in IgG4 takes place during desensitization.

IgG can also be divided into total and specific. Specific IgG antibodies are produced throughout life after contact with an antigen. Thanks to them, it is possible to diagnose various infectious and autoimmune diseases. In contrast, all specific antibodies belong to total antibodies.

The IgG test checks the concentration of both total and specific IgG. We perform both tests on venous blood, and sporadically we test the level in the cerebrospinal or joint fluid. The level of specific IgG is determined using enzyme immunoassay methods (e.g. ELISA test) or immunofluorescence methods. When testing the concentration of total antibodies, we use the immunonephelometric and immunoturbidimetric methods.

IgG – normy

The laboratory norm for total IgG is age dependent and is:

  1. 1-7 days: 5,83 — 12,7 g/l,
  2. 8 days-2 months: 3,36 – 10,5 g / l,
  3. 3-5 months: 1,93 – 5,32 g / l,
  4. 6-9 months: 1,97 – 6,71 g / l,
  5. 10-15 months: 2,19 – 7,56 g / l,
  6. 16-24 months: 3,62 – 12,2 g / l,
  7. 2-5 years; 4,38 – 12,3 g / l,
  8. 5-10 years: 8,53 – 14,4 g / l,
  9. 10-14 years: 7,08 – 14,4 g / l,
  10. 14-18 years: 7,06 – 14,4 g / l,
  11. over 18 years: 6,62 – 15,8 g / l.

Remember that the test results should always be shown to the doctor. You don’t have to leave your home to do this. It is enough to arrange a convenient and safe remote consultation, also within the framework of the National Health Fund.

IgG – interpretation of results

The causes of too low IgG levels are varied. A low score may be the result of:

  1. gastrointestinal diseases, e.g. celiac disease,
  2. kidney disease, e.g. nephrotic syndrome
  3. cancers, e.g. leukemia
  4. drugs, e.g. antimalarials, cytostatic drugs, glucocorticosteroids,
  5. various infections, e.g. HIV, sepsis,
  6. malnutrition,
  7. severe burns,
  8. diabetes complications.

If the test shows an increased level of IgG, it may be a result of, for example:

  1. inflammation
  2. chronic infection,
  3. autoimmune diseases, e.g. multiple sclerosis,
  4. hematological diseases, e.g. lymphomas, multiple myeloma
  5. liver disease, e.g. cirrhosis.

IgG deficiency – causes

At present, it is not fully known what causes IgG deficiency. It is assumed that genetics may play a key role. Certain medications and other medical conditions can also lead to IgG deficiency.

Read: 5 questions about genetics

Treatment of IgG deficiency depends on the severity and characteristics of the symptoms. If infections are frequent enough, interfere with everyday life, or become severe, your doctor will treat you appropriately, such as antibiotics.

Some people with severe infections may need immunoglobulin therapy to boost the body’s immune system instead of relying on antibiotics.

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