Immunoglobulin G (IgG) Subclass 1, 2, 3, and 4 Concentration (Serum)

Why This Test Matters

IgG is the most abundant antibody in your blood, but it’s divided into four subclasses (IgG1, IgG2, IgG3, IgG4). Each subclass has a unique function. For example, IgG2 helps fight bacterial infections, while IgG3 is involved in activating immune responses. Measuring these levels can help doctors diagnose or monitor conditions like immune deficiencies, autoimmune diseases, or infections.

When Might You Need This Test?

Your doctor may order this test if you have symptoms like frequent infections, unexplained fatigue, or autoimmune conditions. It’s also used to check immune function in people with certain genetic disorders or after treatments like chemotherapy. Sometimes, it’s part of a broader evaluation for conditions like lupus, rheumatoid arthritis, or HIV.

What to Expect During the Test

A small blood sample will be taken from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause much discomfort. The sample is then sent to a lab for analysis. Results are typically ready within a few days.

What the Results Mean

Results show the concentration of each IgG subclass. While specific reference ranges vary by lab, low levels of certain subclasses may indicate immune system issues, while high levels could be linked to certain infections, diseases, or medications. Your doctor will interpret the results in the context of your overall health.