Serum immunoglobulin G subclass

There are 4 subclasses of IgG, namely IgG1, IgG2, IgG3, and IgG4, and their contents decrease 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 the classical pathway. Among them, IgG3 has the strongest ability to activate complement, and IgG4 can be polymerized through alternative pathways. Activate complement. The ability of each subtype 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 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 subclasses are small, it is difficult to prepare subclass antisera. At present, monoclonal antibodies are mainly used for detection. The measurement methods include radioimmunoassay, one-way diffusion method and ELISA method.

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