A guide to immunoglobulin therapy for primary immunodeficiency (PI)

Primary immunodeficiency (PI) refers to a large group of rare genetic defects and disorders that cause problems with the way that the immune system works. There are over 450 recognized types of PI, and this number has been increasing as advances in genetic testing have helped identify more. Primary immunodeficiencies are also known as primary immunodeficiency diseases (PIDDs). More recently, these conditions have been referred to as inborn errors of immunity (IEI).

The age where symptoms begin and the severity of the condition vary depending on the type of PI a person has, but all types of PI disrupt how the immune system works. As a result, a person with PI will be more susceptible to infections and other diseases, and they are more likely to become severely ill from an infection.

Treatment options vary depending on the type of PI. Treatment options also overlap across many types of PI. One of the most commonly used treatment options is immunoglobulin replacement therapy, also called immune globulin replacement therapy.

What is immunoglobulin replacement therapy?

Immunoglobulin replacement therapy is a treatment that helps the immune system work better. It involves regular infusions of a solution that contains high amounts of proteins called immunoglobulins.

Immunoglobulins are also called antibodies. Immunoglobulins circulate in the blood. When one encounters a foreign substance like a virus or harmful bacteria, it attaches to that substance. This helps immune cells identify and eliminate harmful invaders.

The genetic defects that cause PI interfere with the normal production of immunoglobulins, where the immune system may not produce enough immunoglobulins, or produces immunoglobulins that do not function well.

Immunoglobulin replacement therapy provides the body with a supply of healthy immunoglobulins. This helps the immune system function better, reducing the risk of infections and complications. Improving immune system function also allows a person to live a more normal life.

How is immunoglobulin replacement therapy administered?

Immunoglobulins are found in plasma, the liquid component of blood, and immunoglobulin infusions are made from blood collected from blood donors. These products go through extensive purification and testing processes to ensure their safety.

Immunoglobulin replacement therapy can be administered in one of two ways. Some products are delivered as an intravenous infusion (IVIg), or an infusion directly into a vein. These infusions require a visit to a healthcare center.

Other products are delivered as a subcutaneous infusion (SCIg), where a needle is inserted into a layer of fatty tissue under the skin. SCIg infusions can typically be self-administered or administered with the help of a caregiver, after training by a healthcare provider.

The frequency of infusions will depend on the specific product being used.

What other therapies are used to treat PI?

Mentioned above, treatment options will vary depending on the type of PI that a person has and the symptoms they are experiencing. Treatment can involve antibiotic medications and antiviral medications to address or prevent existing infections.

In some cases, a healthcare team may recommend treating PI with a procedure called a hematopoietic stem cell transplant (HSCT), also known as a bone marrow transplant. Gene therapies, treatments that correct genetic defects, may be available through clinical trials for select types of PI.