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What Is an IgG Antibody?

The immune system creates antibodies to destroy invaders.
A person with multiple sclerosis may experience tremors in the hands and feet that make movement and grip difficult.
Multiple sclerosis is a disorder that arises when an individual's immune system attacks the myelin sheaths surrounding axons in the central nervous system.
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  • Written By: Cathy Crenshaw Doheny
  • Edited By: Michelle Arevalo
  • Last Modified Date: 15 October 2014
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Antibodies are proteins made by the immune system to destroy foreign invaders. There are five major types of antibodies: immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM), immunoglobulin E (IgE) and immunglobulin D (IgD). An IgG antibody helps to battle bacterial and viral infections. Comprising up to 80% of the all of these essential proteins, it is the smallest, yet most abundant, human antibody. Found in all bodily fluids, IgG is the only antibody that can protect a fetus by passing through the mother's placenta.

A physician may order a quantitative immunoglobulin blood test to determine the exact level of each type of antibody if the results of either a total blood protein test or serum protein electrophoresis test — which can measure each type of protein in the blood — are abnormal. The doctor may also order a quantitative immunoglobulin test if the patient's symptoms suggest an autoimmune disease, allergies, certain blood cancers, or recurring infections. The test is also used to follow-up on the treatment for Helicobacter pylori (H. pylori) bacteria and to confirm a response to a vaccination already given, to ensure that the patient has achieved immunity to the disease.

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Normal levels of the IgG antibody usually fall in the range of 565–1765 mg/dL (5.65–17.65 g/L). A higher than normal level can suggest an IgG monoclonal gammopathy, such as multiple myeloma — a cancer of the blood and bone marrow — or monoclonal gammopathy of undetermined significance (MGUS) — a benign, but sometimes pre-malignant condition. Elevated IgG antibody levels may also suggest the presence of a chronic infection with an illness such as AIDS or hepatitis. Multiple sclerosis (MS), a chronic neurological disease of the central nervous system, is another possible diagnosis when the IgG antibody level is higher than normal.

A lower than normal IgG antibody level may suggest some types of leukemia or nephrotic syndrome, which often results in kidney damage. Low levels of the IgG antibody can also be caused by Waldenstrom's macroglobulinemia, a rare blood cancer that is characterized by an overproduction of the IgM antibody and subsequent suppression of production of other types of antibodies, including IgG. In addition, some primary immunodeficiencies are defined by a low level or complete deficiency of IgG. These include: X-Linked Agammaglobulinemia (XLA), a congenital disease in which IgG, IgM and IgA antibody levels are all greatly reduced or non-existent; Common Variable Immunodeficiency (CVID), also known as hypogammaglobulinemia), a condition in which there is a reduction in the number of one or more of the main three antibodies (IgG, IgM or IgA); and Severe Combined Immunodeficiency, a genetic illness that usually presents with a reduction in all classes of antibodies.

Primary immunodeficiencies may be treated with Intraveneous Immunoglobulin (IVIG) therapy, which contains purified IgG antibodies collected from healthy donors. IVIG helps to protect immunodeficient patients by temporarily replacing the antibodies needed to fight infections. IVIG therapy is also used to treat some auto-immune and neurological diseases, such as dermatomyositis/polymyositis, idiopathic thrombocytopenic purpura(ITP), Guillain-Barre syndrome, and chronic inflammatory demyelinating polyneuropathy (CIDP).

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anon940182
Post 11

I am just learning that my IGG Subclass 1 and 2 and the serum were all high and my IGA was undetectable. Is there anything other than cancer this could be? They are running further tests to rule out blood cancer.

anon350572
Post 10

Is there an antibody that can help your spleen turn loose of platelets?

anon328663
Post 9

My wife has been getting ivig since 2006. Recently she has been ill for long periods of time. First they thought it was a mono infection flaring back up. Blood tests indicated no mono. She has been diagnosed with Excessive Daytime Sleepiness, Fibromyalgia, PTSD, TMJ, Scoliosis, etc., in the past. This week she had a PET/CT scan because her immunologist suspects her spleen is swollen.

I hate to say it but I wonder if it's really Leukemia being misdiagnosed for years. A year before my son was born she had a conization for carcinoma in situ. Cancer runs on both sides of her family. It really freaked out and waiting on additional blood tests and the scan. I don't know what I'm going to do if it's progressed too far and it's terminal. I just don't understand why people don't get referred to a hematologist sooner when IGG deficiencies are present. Maybe it's because some of the things currently known weren't before?

anon328290
Post 8

Will high levels if IgG always be detected in HIV positive individuals?

anon318768
Post 7

Well, they found a mass on my lung and a low IgG. I should know more soon.

anon258771
Post 6

What does an igm test result of 350 h mean?

anon243222
Post 5

Thank you. Being a nurse, I need a service that is not as detailed as a doctor needs but more informative that what most patients need.

anon158899
Post 4

I was diagnosed with MS many years ago. My doctor just checked my IGG and the results came back normal. I have been on Betaseron since 1997. Could that alter my IGG since it is a interferon?

ysmina
Post 3

@turquoise-- chlamydia refers to a group of infections, some of which are transmitted sexually. "Chlamydia trachomatis" is one for example. Chlamydia igg antibodies in the blood mean that this person has been exposed to this infection in the past. They often check for this in pre-marriage health checkups and also if a couple is having trouble getting pregnant. Hope this helps!

turquoise
Post 2

We're learning about sexually transmitted diseases and the chapter talks about chlamydia igg antibody. What is that? How does this antibody come about? Can anyone comment?

faithstewart
Post 1

If adding the human igg antibody to the blood stream helps protect the immuno deficient from infection, I wonder if it is possible to increase immunity to common viruses by increasing the antibody in those with healthy immune systems? I am sure if it was possible it would have already been thought of, but it seems like it would work.

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