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Some Types of PI:

IgG Subclass Deficiency

Immunoglobulins make up the antibodies in the blood that fight infection. There are five main types of immunoglobulins, or Ig: IgG, IgA, IgM, IgD, and IgE. Each type helps the immune system fight infection in a specific way.

Most of the antibodies in the blood and other fluids that surround the body’s tissues and cells are of the IgG class. The IgG class is further divided into four subclasses, including IgG1, IgG2, IgG3, and IgG4. People are said to have an IgG subclass deficiency when they lack or have very low levels of one or two IgG subclasses but have normal levels of other immunoglobulins. It’s not clear how or if IgG subclass deficiencies are passed down through families. Males and females can both be affected, and sometimes, two people with IgG subclass deficiencies are found in the same family. Or one person in the family could have IgG subclass deficiency, and another family member could have a different type of primary immunodeficiency (PI).

What do the different immunoglobulins do?

Example of immunoglobulins.

There are five classes of immunoglobulins (Ig) that help the body fight infection:


IgM antibodies are the first to respond. They offer important protection during the early days of infection. These antibodies tend to stay in the bloodstream, where they aid in killing bacteria, viruses and fungi.


IgG antibodies are the next to respond. These antibodies are formed in large quantities and work in the blood and tissues of the body. They bind to pathogens so that the immune cells have an easier time destroying them. IgG antibodies can pass from a mother to her unborn baby through the placenta.


IgA antibodies are secreted in body fluids such as tears, saliva, and mucus. They protect against infection in the respiratory tract and intestines. These antibodies can pass from mothers to newborns through breast milk.


IgD antibodies may be present on the surface of B cells, but their function is not fully understood at this time.


IgE antibodies are normally present in trace amounts and are important in allergic reactions.

Each IgG subclass plays a slightly different role in protecting the body against infection, so a person lacking a specific IgG subclass will be vulnerable to certain kinds of infections but not others.

  • The IgG1 and IgG3 subclasses contain antibodies against serious bacterial infections like diphtheria and tetanus, as well as antibodies against viruses
  • The IgG2 subclass contains antibodies against bacteria that cause ear and sinus infections, pneumonia, and blood infections
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Symptoms of IgG subclass deficiency

Recurring ear and sinus infections, bronchitis, and pneumonia are the most common infections in people with IgG subclass deficiencies.

Diagnosis of IgG subclass deficiency

It’s possible to have no or very low levels of one or more IgG subclasses while maintaining a normal level of total IgG, IgM and IgA. You can determine the immunoglobulin levels in the body by receiving an immunoglobulin blood test (IgG test). A person is considered to have a selective IgG subclass deficiency if blood levels of one or more of the IgG subclasses are below the normal range based on age, and if the levels of other immunoglobulins (total IgG, IgA, and IgM) are normal or near normal.

It’s important to remember that the definition of “normal” IgG subclass concentrations varies over time and from lab to lab. Normal values usually represent a small range below and above the average for a person’s age.

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What should I know about treatment for IgG subclass deficiency?

You are not alone, but no one is quite like you. It's important to learn about the various treatments for PI, and should be individualized to meet your specific needs. Your healthcare team is there to provide recommendations based on you, and your situation. Here are some tips:

  • Keep track of how you’re doing and share the information with your doctor on a regular basis.
  • Your doctor will only know how you’re doing if you tell them. If you have questions, concerns, thoughts or feelings—speak up and share!
  • You and your doctor both play a part in managing your health. You can take an active role by learning as much as you can and by following your doctor’s recommendations.
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You know more about you, and your doctor knows more about medicine, so together you will work to find the best plan for you.
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What’s your plan?

If you or a loved one has been diagnosed with PI, a doctor can help you craft a treatment plan that’s right for you. Explore treatment options here.

Types of Treatment

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Kristi B., 49

Virginia Beach, VA

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