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Reference Guide
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IgG4
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Immunoglobulin G4

What's 
IgG4
?
Immunoglobulin G4, often abbreviated as IgG4, is a type of protein that plays a vital role in your immune system. It's one of the four subclasses of Immunoglobulin G (IgG), which are the antibodies that your body produces to fight off infections. Think of IgG4 as a special agent in your body's defense system, always on the lookout for harmful invaders like bacteria and viruses. Once it spots an invader, it sends out an alert to other parts of your immune system to join the fight. IgG4 helps keep you healthy by ensuring your body is always ready to defend itself against harmful foreign substances.
If Your Levels Are High
High levels of Immunoglobulin G4 (IgG4) in your blood could indicate that your immune system is overactive, potentially due to a condition known as IgG4-related disease. This disease is a rare inflammatory condition that can affect various parts of your body, causing swelling and damage. It's not entirely clear why some people's bodies produce too much IgG4, but it could be related to certain genetic factors or external triggers like infections or certain medications. For instance, some drugs, such as phenytoin (used for epilepsy) and penicillamine (used for rheumatoid arthritis), have been known to stimulate the production of IgG4. High IgG4 levels could also be associated with other conditions like allergies, autoimmune diseases, and certain types of cancer. Therefore, an elevated IgG4 level doesn't automatically mean you have IgG4-related disease, but it's a clue that your immune system might be responding to something.
Symptoms of High Levels
Symptoms of high levels of Immunoglobulin G4 could include persistent fatigue, unexplained weight loss, skin rashes, joint pain, and swelling in various parts of the body.
If Your Levels are Low
Immunoglobulin G4, or IgG4, is a protein our bodies make to help fight off infections and diseases. Think of it as one of your body's soldiers in its defense army. Sometimes, though, our bodies might make too much of this soldier, which can cause health issues. This is where an IgG4 biomarker test comes in. It's a simple blood test that checks how many IgG4 soldiers you have. If you have too many, you might have a condition called IgG4-related disease, which can affect different parts of your body. This test is a way for us to figure out if this is what's going on. Now, if your IgG4 levels are low, it could mean your body isn't producing enough of these soldiers to fight off infections or diseases. This could be due to certain medications, like immunosuppressants, or conditions that affect your immune system.
Symptoms of Low Levels
Symptoms of low levels of Immunoglobulin G4 could include frequent infections, fatigue, and general feelings of being unwell.

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