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For people with certain primary immunodeficiency (PI) disorders — also called inborn errors of immunity (IEI) — the immune system can’t produce enough working antibodies, which are immune system proteins that help fight infections.
Immunoglobulin (Ig) replacement therapy helps replace some of those missing or low antibodies. The treatment uses antibodies made from donated human plasma (the liquid part of blood) to help prevent recurrent (repeated) infections and support quality of life.
For many people with PI, Ig replacement therapy isn’t a short-term fix. It may be a lifelong treatment.
“Immunoglobulin” is another word for “antibody” — a protein your immune system uses to identify and neutralize germs like bacteria and viruses. When the body can’t produce enough working antibodies, immunoglobulin replacement therapy can help by supplying them from donated human plasma.
The terms “immunoglobulin replacement therapy” and “antibody replacement therapy” are used interchangeably.
Ig replacement therapy is a standard treatment approved by the U.S. Food and Drug Administration (FDA) for people with PI whose bodies can’t produce enough working antibodies — a condition called antibody deficiency.
Ig replacement therapy is most commonly used to treat:
Immunoglobulin treatment may also benefit some people with other types of primary antibody deficiencies, such as selective IgM deficiency and specific antibody deficiency.
Selective IgA deficiency isn’t usually treated with immunoglobulin replacement, because standard products are mostly immunoglobulin G (IgG) and don’t replace immunoglobulin A (IgA). Ig therapy may be considered in select cases, but this should be handled by an immunology specialist.
Ig replacement therapy delivers ready-made antibodies made from donated human plasma pooled from thousands of donors. This helps provide a broad range of antibodies against different germs.
Between 95 percent and 98 percent of the antibodies in these products are IgG, the type that mainly helps protect against bacteria and viruses. Small amounts of IgA and IgM may also be present.
Donors and plasma are screened for infectious diseases during the collection and manufacturing process. Manufacturers also use steps to inactivate or remove certain viruses, which helps lower the risk of infection from treatment.
After you receive Ig therapy, the antibodies can give you extra protection for about two to four weeks, depending on the type of treatment and your dosing schedule. After this time, antibody levels begin to drop and the dose needs to be repeated for continued protection.
This treatment only temporarily replaces missing antibodies. Ig therapy can help reduce how often infections happen and how severe they are. This may help lower the risk of long-term problems, such as lung damage from repeated respiratory infections. It doesn’t prompt your body to make its own antibodies.
Before you and your doctor choose among treatment options, there are two key steps.
Your doctor will run immune studies. This typically involves measuring antibody levels before and after a vaccine (such as the pneumococcal vaccine) to assess your immune system’s response.
These tests should usually be completed before starting Ig therapy. After Ig therapy starts, accurate antibody testing can be difficult because the treatment adds donor antibodies to your blood.
Your immunologist will start you on a dose based on your weight, then adjust the dose based on:
The goal is to keep Ig levels consistently above a personalized target threshold.
Ig replacement therapy is given in one of two ways — intravenously (through a vein, called IVIG) or subcutaneously (under the skin, called SCIG).
Both methods can be effective, and the right choice depends on your lifestyle, preferences, health needs, and how you tolerate each method. Your doctor will consider these factors when prescribing immunoglobulin replacement therapy.
For people who want less frequent dosing, facilitated SCIG uses hyaluronidase — a protein that helps the medication spread and absorb under the skin. This allows a larger dose to be given at once, often every three to four weeks.
Facilitated SCIG is typically given with training or support from a healthcare professional, depending on the product and care plan.
Adverse reactions (side effects) are more common in IVIG than with SCIG. With IVIG, many side effects that occur during infusion are related to the speed of the infusion rate. Some reactions may also be related to the product, dose, hydration, or a person’s overall health at the time of treatment.
Systemic (whole-body) IVIG infusion side effects include:
IVIG side effects are more likely in certain circumstances, including:
In most cases, slowing down the infusion rate reduces side effects. If side effects don’t improve, your healthcare provider may recommend switching to another brand of IVIG.
Your healthcare provider can also recommend medications to help prevent side effects, such as:
People who can’t tolerate IVIG may ask their doctor whether SCIG is an option. SCIG often causes fewer whole-body side effects than IVIG, but it can cause local reactions at the infusion site, such as:
On myPIteam, people share their experiences with primary immunodeficiency disorders, get advice, and find support from others who understand.
Have you experienced side effects from immunoglobulin replacement therapy? Let others know in the comments below.
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