Immunoglobulin G

IgG is the most common antibody found in the blood and tissue fluid. It plays a central role in the immune response by neutralizing pathogens and forming immunological memory. The laboratory value measures the concentration of IgG in the blood and provides information about the immune status and chronic infections.

An IgG test is recommended for: • People with recurrent infections (e.g. respiratory infections, sinusitis) • Patients with suspected immunodeficiencies • Monitoring of vaccine responses or immunotherapies • Diagnosis of autoimmune diseases or chronic infections • Patients with suspected chronic inflammation or infectious diseases (e.g. toxoplasmosis)

The test serves the diagnosis of immunodeficiencies, autoimmune diseases and chronic infections. It is also used to evaluate the immune status after a vaccination.

A high IgG level often indicates: • Chronic infections (e.g. hepatitis, tuberculosis) • Autoimmune diseases such as lupus or rheumatoid arthritis • Chronic inflammation A low IgG level can be caused by: • Primary or secondary immunodeficiencies • Chronic diseases such as nephrotic syndrome or renal loss Symptoms of abnormal IgG levels can include: • Frequent or severe infections • Persistent fatigue with chronic inflammation

The testing can be carried out independently of the time of day. A serial measurement is helpful to monitor changes in the immune status.

• IgG is divided into four subclasses (IgG1 to IgG4), which fulfill specific functions. Deviations in the subclasses can enable more accurate diagnoses. • A deficiency in IgG can be caused by genetic defects or certain medications. • Chronically elevated IgG levels can occur in chronic infections or certain types of cancer (e.g., myeloma).