Immunoglobulin G (IgG)

Immunoglobulin G (IgG) is a protein that acts as an antibody and is created by plasma cells and lymphocytes. Immunoglobins assume a pivotal role in the body’s immune system as they help the body get rid of bacteria and microbes by attaching themselves to such outside substances and eliminating them. Immunoglobins can live either on the peripherals of the cells or can circulate openly in the blood. It is the circulating immunoglobulins that are termed antibodies.

Immunoglobins are divided into different types called isotypes. There are five Immunoglobulin Isotypes which are – IgA, IgD, IgE, IgG, and IgM. The different types of Immunoglobulins have diverse natural properties, areas of functioning, and reactions to the various types of antigens.

This test measures the level of Immunoglobulin G (IgG) Antibodies in the blood.  IgG is the smallest and most common type of antibody making up 75-80% of all antibodies in the body.  IgG antibodies are found in all body fluids and play a key role in fighting infections from bacteria and viruses.

What Is Immunoglobulin G?

Immunoglobulin G or IgG is one of the isotypes of Immunoglobulin. IgG is one of the most common antibodies in blood circulation and represents nearly 75% of serum antibodies. The Immunoglobulin G is produced by plasma B cells and is crucial to the protection of body tissues against infection. It also protects the fetus in utero from any infection. Immunoglobulin G is also responsible for the regulation of allergic reactions and can also prevent IgE-mediated anaphylaxis. There are four subtypes of IgG named – IgG1, IgG2, IgG3 and IgG4.

In some people owing to certain health conditions the body produces low levels of Immunoglobulin G causing IgG deficiency. People with IgG deficiency are prone to infections like;

• Sinus infection
• Gastrointestinal Infection
• Ear Infection
• Pneumonia
• Bronchitis
• Infections leading to throat infections

IgG deficiency can be seen in people suffering from kidney damage, leukemia, or other infections that make the immune system weak making the body susceptible to further infections.

High levels of IgG mean chronic infection like HIV/AIDS. The elevated IgG levels can also be due to Multiple sclerosis, autoimmune disorders, and some types of cancer.

What Is the Immunoglobulin G Test / What Is the Igg Test?

The Immunoglobulin G test is also known by several names like IgG Serum, Quantitative IgG, IgG Test, and Serum. It is a simple blood test that measures the level of Immunoglobulin G antibodies in the blood. The IgG Serum test is performed to determine the presence of any infection in the body and the level of immunity of our body.

Why Do You Need Immunoglobulin G Test?

Several reasons necessitate the use of the IgG test;

• It helps in ascertaining whether the individual has been exposed to illness or not.
• It helps in determining the immunity level post-recovery from an illness or post-vaccination.
• This test is also helpful in chronic inflammation cases
• In recurring infection cases
• If the infection caused is assumed to be due to IgG antibodies.

Igg Test Preparation

No special preparation is required for this test, although it is advised to inform your doctors.

Igg Test Procedure

The Immunoglobulin G test is a fairly simple blood test that requires a blood sample, which is usually drawn out from the veins of the forearm. This blood sample is then sent for pathological testing. 

Immunoglobulin G Normal Range

The immunoglobulin G normal range varies with age and here are the IgG normal range for different age groups;

• The IgG normal range for age 0-1 years is between 231-1411 mg/dL
• The IgG normal range for ages 1-3 years is between 453-916 mg/dL
• The Immunoglobulin normal range for ages 4-6 years is between 504-1464 mg/dL
• The Immunoglobulin normal range for age 7-9 years is between 572-1474 mg/dL
• The IgG normal range for ages 10-11 years: is between 698-1560 mg/dL
• The IgG normal range for age 12-13 years is between 759-1549 mg/dL
• The IgG normal range for age 14-15 years is between 716-1711 mg/dL
• The IgG normal range for age 16-19 years is between 549-1584 mg/dL
• The IgG normal range  for people older than 19 years of age is between 700-1600 mg/dL

High IgG levels may indicate that a person has a chronic infection such as HIV or Hepatitis.  They can also be high due to conditions such as Multiple Sclerosis, some types of cancer, and autoimmune disorders.  Low IgG levels can be found in people with kidney damage, leukemia, and conditions that weaken the immune system leaving them more susceptible to infections.

IgG test results cannot indicate the specific type or source of an infection.  More specific testing may be needed as a follow-up to abnormal results.  An IgG test may be ordered when someone is suffering from frequent infections to see if they have a condition that is impairing their immune system.

What are IgG deficiencies?

An IgG deficiency is a health problem in which your body doesn’t make enough Immunoglobulin G (IgG). People with IgG deficiency are more likely to get infections.

When your body feels it is under attack, it makes special proteins called immunoglobulins or antibodies. These antibodies are made by the plasma cells. They are let loose throughout the body to help kill bacteria, viruses, and other germs. The body makes 5 major types of immunoglobulins:

• Immunoglobulin A
• Immunoglobulin G
• Immunoglobulin M
• Immunoglobulin D
• Immunoglobulin E

Immunoglobulin G (IgG) is the most common type. IgG has 4 different subclasses, IgG1— 4. IgG is always there to help prevent infections. It’s also ready to multiply and attack when foreign substances get into the body. When you don’t have enough, you are more likely to get infections.

What causes IgG deficiencies?

It’s not known what causes IgG deficiency. However, genetics may play a role. This condition is also thought to be linked to another immunoglobulin deficiency.

What are the symptoms of an IgG deficiency?

Infections that most often affect people with IgG deficiency are:

• Sinus infections and other respiratory infections
• Gastrointestinal infections
• Ear infections
• Pneumonia
• Bronchitis
• Infections that result in a sore throat
• Rarely, severe and life-threatening infections

In some people, infections cause scarring that harms the airways and lung function. This can affect breathing. People with IgG deficiency also often find that pneumonia and the flu vaccines don’t keep them from getting these infections.

How is an IgG deficiency diagnosed?

A blood test that measures immunoglobulin levels can diagnose IgG deficiency. It’s possible to have a normal level of total IgG, so the testing of the IgG subclasses is important. Tests can also be done on saliva and cerebrospinal fluid. But, a blood test is the most common.

How is an IgG deficiency treated?

Treatment depends on how bad your symptoms and infections are. When the symptoms come on later in life, the health problem is harder to manage. The person also tends to have more infections.

If infections are not getting in the way of your daily life, treating them right away may be enough. If you get frequent or severe infections that keep coming back, you may do well with ongoing treatment. This will help to prevent sickness or reduce symptoms or frequency. This may mean taking a daily antibiotic to ward off infections. You may need to alternate between other antibiotics if infections and symptoms still happen.

Some people who suffer from severe infections may be resistant to antibiotic treatment. They may need immunoglobulin therapy to help boost the body’s immune system rather than relying on antibiotics to prevent infections. 

Key points

• Immunoglobulin G, also known as IgG, is the most common type of IgG deficiency.
• People with IgG deficiency are more likely to get infections.
• Although it’s not known what causes IgG deficiency, genetics may play a role.
• A blood test that measures immunoglobulin can diagnose this condition.
• When the symptoms come on later in life, the health problem is harder to manage, and the person tends to have more infections.
• Treatment depends on how bad your symptoms and infections are.

    Immunoglobulin G Test Interpretation

The immunoglobulin G test result is interpreted in terms of high or low. The high IgG levels can be due to infections in the body or due to autoimmune disorders like Cirrhosis and as a reaction to certain substances. The low levels of IgG indicate the loss of protein from the body, which can be due to some disease or trauma like burns or may be due to diabetes.

IgG tests are not specific and although they can signal infections and autoimmune disorders, they cannot exactly pinpoint the reason behind the abnormal IgG levels hence, other tests are needed to be done in conjunction with this particular test.