Gammaglobulin therapy, often called Immunoglobulin (Ig) therapy, involves administering a purified protein product derived from human blood plasma. Gammaglobulins are a classification of proteins that includes antibodies, which are molecules naturally produced by the immune system to fight off infection and disease. When a person’s body cannot create enough of these protective proteins, or when their immune system is malfunctioning, therapeutic gammaglobulin is used to supply the necessary defense components. This treatment provides a concentrated dose of diverse antibodies to support immune function.
The Natural Function of Gammaglobulins in the Body
Gammaglobulins are protective proteins (immunoglobulins) that circulate throughout the blood and lymphatic systems. These molecules are manufactured by specialized white blood cells called plasma cells. Their primary function is to identify and neutralize foreign invaders, such as viruses, bacteria, and toxins, through molecular binding. There are five major classes of immunoglobulins (IgA, IgD, IgE, IgG, and IgM), but Immunoglobulin G (IgG) is the most abundant, accounting for approximately 75% of all circulating antibodies. IgG is important because it is long-lasting, crosses the placenta to protect developing fetuses, and facilitates the destruction of pathogens by signaling other immune cells.
Medical Conditions Treated with Gammaglobulin Therapy
Therapeutic gammaglobulin is prescribed in two main scenarios. The first is replacement therapy for Primary Immunodeficiency (PID) disorders, where the body fails to produce sufficient antibodies. This leaves patients vulnerable to recurrent, severe infections, and conditions like Common Variable Immunodeficiency (CVID) necessitate this treatment to provide an external source of protective antibodies.
The second major use is for immunomodulation in certain autoimmune and inflammatory disorders, which requires significantly higher doses. In these cases, the high concentration of antibodies modulates the overactive immune system, potentially by blocking harmful autoantibodies or dampening inflammation. Examples include Chronic Inflammatory Demyelinating Polyneuropathy (CIDP), Immune Thrombocytopenic Purpura (ITP), Guillain-Barré syndrome, and Kawasaki disease.
Administering Therapeutic Gammaglobulin
Therapeutic gammaglobulin is sourced from the pooled plasma of thousands of healthy, screened human donors. This large pool ensures a broad spectrum of antibodies capable of recognizing common pathogens. The collected plasma undergoes a rigorous purification process, including multiple steps to inactivate or remove potential viruses, resulting in a product that is predominantly purified IgG.
The medication is administered either directly into the vein (Intravenous Immunoglobulin, or IVIG) or under the skin (Subcutaneous Immunoglobulin, or SCIG). IVIG is infused every three to four weeks in a clinic or home setting, often requiring several hours per session. This method delivers a high dose quickly, resulting in an immediate peak in antibody levels followed by a gradual decline.
SCIG involves injecting smaller, more frequent doses—usually weekly or biweekly—into the fatty tissue beneath the skin, often at multiple sites. This method is frequently self-administered at home, offering greater patient independence. Although absorption is slower, SCIG maintains more stable, consistent antibody levels over time, avoiding the high peaks and low troughs associated with IVIG.
Managing Side Effects and Treatment Monitoring
Immunoglobulin therapy is well-tolerated, but patients may experience reactions during or shortly after the infusion. Common, mild side effects often resemble flu-like symptoms and include headache, fever, chills, fatigue, and muscle aches. These systemic reactions are more frequently associated with IVIG due to the rapid infusion of protein.
SCIG leads to fewer systemic side effects, though localized reactions such as temporary redness, swelling, or pain at the injection site are common. To mitigate adverse effects, medical staff advise patients to stay hydrated and may administer pre-medications like acetaminophen or antihistamines. Slowing the infusion rate is also an effective strategy.
Rarely, more serious adverse events can occur, including severe headaches (aseptic meningitis), kidney problems, or thrombotic events like blood clots. Patients with pre-existing risk factors, such as heart disease or high blood pressure, require careful monitoring. Regular monitoring of blood levels and kidney function is necessary to ensure the treatment is safe and effective.