Immunoglobulin G (IgG): role, symptoms of deficiency and excess, blood levels
1. The role of IgG in the body
Immunoglobulin G (IgG) is the most common type of antibody in the blood (70-75% of all immunoglobulins), which plays a key role in humoral immunity.
Main functions:
✔ Long-term protection against infections:
- Primary antibody of the secondary immune response
- Protects against bacteria, viruses, and toxins
✔ Transmission of immunity from mother to fetus:
- The only immunoglobulin that passes through the placenta
- Provides protection for the newborn in the first months of life
✔ Activation of immune mechanisms:
- Binds the complement (classic way)
- Stimulates phagocytosis (opsonization)
- Provides antibody-dependent cellular cytotoxicity (ADCC)
IgG Subclasses:
- IgG1 (65%) – the main response to proteinsProteins are high-molecular organic substances consisting of alpha-amino acids linked in a chain by a peptide bond. In living organisms, the amino acid composition of proteins is determined by the genetic code. During synthesis, 20 standard amino acids are used in most cases. Many combinations of them determine the great diversity of properties of protein molecules. Proteins play a key role in the immune response and can perform transport, storage, catalytic, structural, and receptor functions. Proteins are an important part of the nutrition of animals and humans. The main sources of proteins are meat, poultry, fish, milk, nuts, legumes, and grains.
- IgG2 (25%) – response to polysaccharides
- IgG3 (6%) – a strong complement activator
- IgG4 (4%) – involved in allergic reactions
2. Symptoms of IgG deficiency
Reasons:
- Primary immunodeficiency (general variable immune deficiency, hyper-IgM syndrome)
- Secondary immunodeficiency disorders (HIV, leukemia, nephrotic syndrome)
- Taking immunosuppressants
Clinical manifestations:
- Frequent bacterial infections (pneumonia, sinusitis, otitis media)
- Recurrent viral infections
- Chronic gastroenteritis
- Autoimmune diseases (rheumatoid arthritis, SLE)
- Allergic reactions
3. Symptoms of excess IgG
Reasons:
- Chronic infections (tuberculosis, HIV, malaria)
- Autoimmune diseases (rheumatoid arthritis, SLE)
- IgG-type multiple myeloma
- Paraproteinemia
- Liver diseases (chronic hepatitis)
Clinical manifestations:
- For myeloma:
- Bone pain
- Anemia
- Kidney failure
- Hypercalcemia
- Blood hyperviscosity syndrome:
- Headaches
- Visual disturbances
- Neurological symptoms
- Autoimmune manifestations
4. IgG standards in the blood test
| Population group | Reference values (g/L) |
|---|---|
| Adults | 7.0–16.0 |
| Newborns | 3.0–17.0 |
| 1–3 months | 2.0–9.0 |
| 4–6 months | 2.0–7.0 |
| 7–12 months | 2.0–11.0 |
| 1–3 years | 4.0–12.0 |
| 4–6 years | 5.0–13.0 |
| 7–9 years | 6.0–14.0 |
| 10–13 years | 7.0–15.0 |
| 14–16 years | 7.0–16.0 |
Notes:
- The level of IgG in newborns corresponds to the maternal level
- The minimum values are observed in 3-6 months
- Adult levels are reached by the age of 16
5. When is the test scheduled?
- Suspected primary or secondary immunodeficiency
- Recurrent bacterial infections
- Diagnosis of myeloma and other paraproteinemias
- Control of autoimmune diseases
- Assessment of post-vaccination immunity
- Diagnosis of intrauterine infections (determination of specific IgG in the fetus)
6. Additional research
- Electrophoresis of serum proteins
- Immunofixation
- Defining IgG Subclasses
- Evaluation of specific antibodies
7. Approach to treatment of disorders
If there is a shortage:
- Substitution therapy (intravenous immunoglobulins)
- Infection prevention
- Treatment of concomitant diseases
If there is an excess:
- For myeloma- chemotherapy
- In autoimmune processes- immunosuppression
- For hyperviscosity syndrome- plasmapheresis