Immunoglobulin IgG

Key Aspects of IgG Immunoglobulin

• Main Function: IgG protects the body by opsonizing bacteria (making them easier to destroy), fixing complement, and neutralizing toxins. It is critical for the secondary immune response, developing 24–48 hours after antigen stimulation to provide rapid, long-lasting immunity.
• Normal Levels: While ranges vary by lab, adults typically have 600–1600 mg/dL. IgG is the only immunoglobulin that crosses the placenta, providing newborns with passive immunity for their first six months.
• Deficiency Symptoms: Low IgG (hypogammaglobulinemia) can lead to recurrent infections, such as pneumonia, bronchitis, and ear infections.
• Role in Autoimmune Diseases: Elevated IgG can indicate autoimmune disease activity, where the body mistakenly produces antibodies against its own tissues. In cases like Multiple Sclerosis, it is measured in the cerebrospinal fluid (CSF).
• Treatment for Deficiency: Treatment for IgG deficiency focuses on reducing infections and often includes antibiotic treatment or IgG replacement therapy.

IgG Subclasses

IgG is further divided into four subclasses, ordered by decreasing abundance, which possess unique protective functions:

• IgG1: 65% of total IgG.
• IgG2: Crucial for defense against encapsulated bacteria.
• IgG3: Effective in immune complex formation.
• IgG4: Involved in modulating immune responses.