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Immunoglobulin G (IgG)

Immunoglobulin G (IgG) is the most abundant type of antibody in the bloodstream and is produced by plasma cells in response to an infection or immunization. It plays a key role in the immune system's defense against infections by binding to and neutralizing harmful pathogens such as bacteria and viruses. IgG antibodies are highly specific and can recognize and bind to a wide range of pathogens. They can also activate complement, a group of proteins that help to destroy invading pathogens. IgG antibodies are the only type of antibody that can cross the placenta, providing passive immunity to the developing fetus. Tests for IgG antibodies can be useful in diagnosing infections and monitoring the immune response to immunizations. For example, an IgG test for a specific pathogen can help determine if a person has been previously exposed to the pathogen and has developed immunity to it. Low levels of IgG antibodies can occur in some medical conditions, such as primary immunodeficiencies, which are genetic disorders that affect the immune system's ability to produce antibodies. High levels of IgG antibodies may be seen in some autoimmune diseases and chronic infections.

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