Immunoglobulin G Blood Test

What is the purpose of this test?

Order this Immunoglobulin G (IgG) Blood Test, QN, to measure the blood's immunoglobulin G (IgG) levels to assess the immune system status and detect or monitor a deficiency or excess. Immunoglobulins, commonly known as antibodies, are vital to the body's immune system. These immunoglobulins are proteins produced by plasma cells in the immune system as a response to harmful antigens (bacteria or viruses) that cause infections or illnesses. 

When an individual becomes infected or exposed to an antigen, their immune system recognizes the microorganism or substance as foreign. As a result, it stimulates the plasma cells to produce specific immunoglobulins (antibodies) that combat the invaders. Suppose the individual is exposed to the antigen again. In that case, the immune system "recognizes" the antigen encountered, which allows for the immediate production of more antibodies to help stop re-infection.

What does this test measure?

This Immunoglobulin Blood Test screens one of the most common immunoglobulins, IgG. This immunoglobulin type represents a specific group of antibodies with a special function. This test screens for the following immunoglobulin:

• Immunoglobulin G (IgG) – IgG is mainly found in the blood. IgG antibodies are produced in response to an active infection or recent exposure to an antigen. IgG antibody levels peak a few weeks after the infection begins, then decrease and stabilize. The body maintains a certain level of IgG antibodies that can be instantly produced once exposed to the same antigen again, creating long-term protection against infections. Vaccinations replicate this process by exposing individuals to weakened IgG antibodies and stimulating antigen recognition. There are four IgG subtypes: IgG1, IgG2, IgG3, and IgG4.

What causes an immunoglobulin G deficiency or excess?

Individuals may acquire an immunoglobulin G deficiency through an underlying condition, usage of certain medications, or other contributing factors that prevent immunoglobulin production. In addition, a deficiency may be inherited through a rare genetic disorder. The following conditions are associated with an immunoglobulin G deficiency:

• Kidney disease
• Diabetes
• Nephrotic syndrome
• Usage of immunosuppressant drugs, phenytoin, and carbamazepine
• Short-term developmental delay in premature infants
• Gastrointestinal issues that affect digestion or absorption of proteins

However, an individual may also experience excessive IgG levels (monoclonal increase) due to several conditions. The following conditions are related to excessive IgG levels:

• Acute or chronic infections
• Autoimmune disorders
• Cirrhosis
• Inflammatory disorders
• Hyperimmunization reactions
• Wiskott-Aldrich syndrome
• Congenital infection (syphilis, toxoplasmosis, rubella, CMV)
• Multiple myeloma
• Chronic lymphocytic leukemia (CLL)
• MGUS (monoclonal gammopathy of undetermined significance)
• Lymphoma
• Waldenstrom's macroglobulinemia