IgG Subclass 2

An immunoglobulins test usually measures the three main types of immunoglobulin (Ig) antibodies that your body makes.

IgG is the most common antibody in your blood. It is made up of four subclasses called IgG1, IgG2, IgG3, and IgG4. IgG2 makes up about a quarter of all IgG and plays a special role: it makes most of the antibodies that fight bacteria with sugary outer coats, such as Streptococcus pneumoniae and Haemophilus influenzae type b.

You may need this test if you have symptoms of low immunoglobulin production, especially repeated sinus, ear, or lung infections - one of the most common reasons providers order an IgG2 level.

Your provider will compare your levels of IgM, IgG, and IgA. Your results can mean different things, depending on your symptoms, any conditions you may have, and which immunoglobulins are high or low. An immunoglobulins blood test alone cannot diagnose any conditions. So if your results aren't normal, you'll probably need more testing to find out what's affecting your immune system.

A low IgG2 level can be linked to repeated sinopulmonary infections (such as sinusitis, ear infections, and pneumonia), especially with poor antibody responses to vaccines made of bacterial sugars (polysaccharides). It can occur alone or together with low IgA. A small dip below the normal range without symptoms is often not a problem.

Higher than normal IgG2 is usually not specific to a particular condition. It can be seen with chronic infection, inflammation, or autoimmune diseases.

If your immunoglobulin levels aren't normal, it doesn't always mean you have a condition that needs treatment. Certain medicines can affect your results. If you have questions about your results, talk with your provider.