Inflammation and immunity
IgG2
One of the four subclasses of the antibody IgG; used when looking into an immune disorder.
Everything about this testWhat it measures
IgG is the most common antibody in the blood and consists of four subclasses: IgG1 to IgG4. This test only measures the amount of IgG2, in grams per liter. IgG2 is the subclass made mainly against the sugar coat (the capsule) of bacteria such as pneumococcus and Haemophilus influenzae. A shortage of this particular subclass can therefore go together with repeated airway and sinus infections, while the total IgG is normal.
- Support when an immune disorder is suspected in people with constantly recurring airway, sinus or ear infections
- An addition to total IgG, IgA and IgM if these are normal but the symptoms persist
High
A raised IgG2 is rarely a problem on its own. The amount of antibodies rises during and shortly after an infection, and also with longer-lasting inflammation or an autoimmune disease. According to the Dutch Society for Clinical Chemistry (NVKC), a strongly raised value of one antibody type can be a reason to look further into the composition of the antibodies with protein electrophoresis. Without symptoms and with normal other values, a slightly raised IgG2 usually has no significance.
Low
A low IgG2 means you have less of this subclass than usual. This only matters if there are also symptoms: constantly recurring or long-lasting airway, sinus or ear infections, especially with bacteria that have a sugar capsule. In young children, a low IgG2 is often a sign of immaturity that goes away on its own, because this subclass develops later than the others. A low IgG2 can also be due to protein loss through the kidneys or the bowel, certain medicines or a bone marrow disease. Without infections, a low value usually has no consequences.
If your result is abnormal
With a low value together with recurring infections, the doctor usually also has the other subclasses, total IgG, IgA and IgM measured and checks whether protein loss or medicine use is involved. After that, you are often referred to an immunologist or lung specialist, who can test whether the immune system makes enough antibodies after a vaccination. Without infections, treatment is usually not started for an abnormal value.
Reliability
The meaning of an abnormal subclass value in people without symptoms has been little studied, and what counts as normal depends strongly on age. A result mainly means something in someone who has strikingly frequent or severe infections and in whom the standard antibody tests (IgG, IgA, IgM) give no explanation. A single subclass value says little: what counts is whether the immune system makes enough antibodies after a vaccination, and that is tested with a separate test. In people without symptoms, the predictive value is low and an abnormal result rarely leads to treatment.
Limitations
- The reference values depend strongly on age; in children, IgG2 is naturally lower and only rises in the course of childhood.
- The amount of antibodies rises during and shortly after an infection; measuring during an infection gives a distorted picture.
- Protein loss through the kidneys or bowel, certain medicines such as corticosteroids and immunosuppressants, and bone marrow diseases lower the value.
- Laboratories use different methods and reference values for subclasses; results cannot simply be compared.
How common is this
Inborn immune disorders are rare. An isolated low IgG2 is found regularly without the person having any problems, and in young children it often goes away on its own. Recurring airway and sinus infections, on the other hand, are very common and usually have another cause, such as allergy, smoking or a virus.
Who is this useful for
Useful in people who have strikingly frequent or severe bacterial infections, especially of the airways, sinuses and ears, and in whom the standard antibody tests give no explanation. A single IgG2 value says the most together with other immune tests, such as the response to a vaccination. In people without such infections, a single IgG2 value adds nothing.
Downsides and risks
- An abnormal IgG2 in someone without recurring infections usually means nothing, but it can cause worry about "a weak immune system" and lead to further testing that is not needed.
- A normal IgG2 value does not rule out an immune disorder; that requires, among other things, testing whether the body makes antibodies after a vaccination.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results