Serum/plasma concentration of immunoglobulin G (IgG) subtypes (specifically IgG1, IgG2, IgG3, IgG4) via immunoassay

Why Might You Need This Test?

Your healthcare provider may order this test if you have symptoms of an immune disorder, such as frequent infections, autoimmune conditions, or if you’re receiving treatment that could affect your immune response. It can also be used to monitor conditions like chronic infections, certain cancers, or after organ transplants.

What Does Each IgG Subtype Represent?

IgG antibodies are divided into four subtypes (IgG1, IgG2, IgG3, IgG4), each with different roles in immunity. IgG1 and IgG2 are most common and provide broad protection, while IgG3 is highly active against bacteria and viruses. IgG4 is less active but can be involved in allergic reactions or autoimmune responses.

What Could Abnormal Results Mean?

Low levels of certain IgG subtypes might indicate a weakened immune system, while high levels could suggest an overactive immune response or certain diseases. For example, low IgG2 could be linked to recurrent sinus or respiratory infections, while elevated IgG4 may be associated with autoimmune conditions or allergic reactions.

How Is This Test Performed?

A blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate serum or plasma, where the IgG subtypes are measured using a sensitive immunoassay technique. Results are compared to reference ranges specific to each subtype.