What Are the Immunoglobulin G Subclasses?

There are 4 subclasses of IgG, namely IgG1, IgG2, IgG3, and IgG4, and their content decreases in order. The physiological characteristics and functions of the four subclasses are also different. For example, IgG1, IgG2, and IgG3 form complexes with antigens to activate complement through classical pathways. Among them, IgG3 has the strongest ability to activate complement, and IgG4 can be polymerized through alternative pathways. Activate complement. The ability of each subclass to pass through the placenta, the ability to bind to Staphylococcus A protein, and the ability to bind to different types of Fc segment receptors are not all the same. They also have different functions in the immune response. For example, IgG1 and IgG3 respond to bacterial and viral antigen proteins, while IgG2 plays a major role in immunizing Streptococcus pneumoniae, Group A streptococcus, and Haemophilus influenzae capsular polysaccharide antigens. In response, IgG4 is related to chronic allergic irritation. Even after desensitization, it can still produce an immune response to allergens and inhibit the production of IgE. IgG subclasses may be related to recurrence of infections, immunodeficiency and autoimmune diseases, so the determination of IgG subclasses is important for these diseases. Even when total IgG levels are within the normal range, IgG subclass assignments can be disrupted. Because the structural differences between the four subtypes are small, it is difficult to prepare subtype antisera. At present, monoclonal antibodies are mainly used for detection. The measurement methods include radioimmunoassay, one-way diffusion method and ELISA method.

There are 4 subclasses of IgG, namely IgG1, IgG2, IgG3, and IgG4, and their content decreases in order. The physiological characteristics and functions of the four subclasses are also different. For example, IgG1, IgG2, and IgG3 form complexes with antigens to activate complement through classical pathways. Among them, IgG3 has the strongest ability to activate complement, and IgG4 can be polymerized through alternative pathways. Activate complement. The ability of each subclass to pass through the placenta, the ability to bind to Staphylococcus A protein, and the ability to bind to different types of Fc segment receptors are not all the same. They also have different functions in the immune response. For example, IgG1 and IgG3 respond to bacterial and viral antigen proteins, while IgG2 plays a major role in immunizing against Streptococcus pneumoniae, Group A Streptococcus and Haemophilus influenzae capsular polysaccharide In response, IgG4 is related to chronic allergic irritation. Even after desensitization, it can still produce an immune response to allergens and inhibit the production of IgE. IgG subclasses may be related to recurrence of infections, immunodeficiency and autoimmune diseases, so the determination of IgG subclasses is important for these diseases. Even when total IgG levels are within the normal range, IgG subclass assignments can be disrupted. Because the structural differences between the four subtypes are small, it is difficult to prepare subtype antisera. At present, monoclonal antibodies are mainly used for detection. The measurement methods include radioimmunoassay, one-way diffusion method and ELISA method.

Name

Serum immunoglobulin G subclass

category

Immunology

Normal serum immunoglobulin G subclass

ELISA method: IgG1: 4.2-12.9g / L IgG2: 1.4-7.5g / L IgG3: 0.4-1.3g / L IgG4: 0.01-1.5g / L

Clinical significance of serum immunoglobulin G subclasses

(1) Increased serum IgG subclasses: IgG4 can increase in allergic diseases, asthma, idiopathic eczema, dermatitis, gallbladder fibrosis caused by chronic Pseudomonas aeruginosa, IgG2, IgG3, and multiple sclerosis IgG1 liter high. (2) Decreased or deficient serum concentration of IgG subclasses: Autoimmune or atopic reactive diseases; IgG2 and IgG3 levels of bronchial asthma in children can be reduced; IgG subtypes of type I diabetes and adolescent diabetes can be reduced; primary The levels of IgG2 and IgG4 in thrombocytopenic purpura are reduced; the levels of IgG3 and IgG4 in systemic lupus erythematosus can be reduced. Immune deficiency: IgG2, IgG4 defects can occur in patients with bone marrow transplantation, HIV infection, and IgA deficiency; IgG1, IgG2, and IgG4 defects can occur in common variable immunodeficiency (CVID); high-dose cortisol hormone application can IgG3 and IgG2 defects occur; IgG4 defects can occur in patients with IgM deficiency; IgG2 defects can occur in radiation injury and chemotherapy; IgG4 defects can occur in Wei-Ao syndrome. Infection: IgG2 defects are prone to otitis media caused by pneumococcal infections in children; IgG2 and IgG4 defects can cause repeated infections of capsular bacteria; lack of IgG2, IgG3, and IgG4 can cause repeated infections of the lungs and bronchitis. Other diseases: Alcoholic liver disease, ataxia-capillary telangiectasia, decreased IgG2, IgG4 content; decreased IgG2 after bowel surgery; decreased IgG1 in advanced renal failure; decreased IgG1, IgG2 in nephrotic syndrome.

Precautions for serum immunoglobulin G subclasses

In summary, the possibility of IgG subclass defects should be considered for all children with recurrent infections, bronchial asthma, and / or chronic obstructive bronchitis. In addition, for all immunodeficiency patients at high risk of infection, such as bone marrow transplantation, IgG subclass levels need to be measured.

Symptoms related to serum immunoglobulin G subclass

Eczema, multiple sclerosis, bronchial asthma, diabetes, thrombocytopenic purpura, systemic lupus erythematosus, lupus erythematosus, ataxia, nephrotic syndrome

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