The immune system is a complex network designed to defend the body against foreign invaders like bacteria, viruses, and fungi. Antibodies, also known as immunoglobulins, are a central part of this defense. IgG deficiency is a condition where the body doesn’t produce enough Immunoglobulin G (IgG), impairing its ability to fight infections and leading to health challenges.
What is IgG and Its Importance?
Immunoglobulin G (IgG) is the most abundant antibody circulating in the blood and extracellular fluid, making up about 75% of all antibodies. These Y-shaped proteins are produced by specialized immune cells called plasma cells. IgG antibodies are a significant component of humoral immunity, the antibody-based part of the immune system that protects against pathogens.
The primary function of IgG is to identify and neutralize various pathogens, including viruses, bacteria, and fungi. They achieve this by binding to the surface of these invaders, immobilizing them or marking them for destruction by other immune cells like phagocytes. IgG also plays a role in activating the complement system, a protein cascade that eliminates pathogens.
IgG provides long-term immunity against infections, allowing the body to “remember” pathogens and mount a quicker, more effective response upon re-exposure. IgG uniquely crosses the placenta from mother to fetus during pregnancy. This provides passive immunity to the newborn, protecting them from infections during their first few months before their own immune system fully develops.
Common Signs of IgG Deficiency
IgG deficiency often manifests as recurrent or unusually severe infections. The respiratory tract is particularly susceptible, leading to frequent episodes of sinusitis, bronchitis, and pneumonia. Ear infections and sore throat infections are also common indicators.
Beyond respiratory issues, individuals with IgG deficiency may experience gastrointestinal infections or susceptibility to various pathogens. Impaired ability to fight common bacteria like Streptococcus pneumoniae and Haemophilus influenzae contributes to these repeated infections. Chronic fatigue or prolonged recovery from illnesses can also be observed.
These symptoms arise because insufficient IgG levels mean the body lacks antibodies to effectively neutralize and clear common invaders. This reduced immune capacity can lead to scarring and damage in the airways and lungs due to persistent inflammation. Standard vaccines for illnesses like pneumonia and the flu may not provide adequate protection for individuals with IgG deficiency.
Diagnosing and Managing IgG Deficiency
Diagnosing IgG deficiency begins with a healthcare provider suspecting an immune issue based on a patient’s history of recurrent or severe infections. Diagnosis involves blood tests to measure overall immunoglobulin levels, specifically IgG. Since total IgG levels can appear normal even with a deficiency, testing specific IgG subclasses (IgG1, IgG2, IgG3, and IgG4) is important for a more precise diagnosis.
An immunologist, a specialist in immune disorders, plays a role in evaluating these test results and determining if an IgG deficiency is clinically significant. Additional tests may assess how well the immune system responds to certain vaccines, determining antibody functional capacity. Low IgG subclass levels in children, especially under five years old, may normalize as they age, but the deficiency can persist in some children and adults.
Management of IgG deficiency depends on the severity and frequency of infections. For mild cases, treating infections promptly with antibiotics may be sufficient. For frequent or severe recurring infections, ongoing treatment is necessary. Prophylactic antibiotics, taken daily, can help prevent infections from taking hold.
In more severe cases, or when antibiotic treatment is not fully effective, immunoglobulin replacement therapy may be recommended. This therapy supplements missing antibodies using IgG derived from donated human plasma. It can be administered intravenously (IVIG) every three to four weeks, or subcutaneously (SCIG) weekly or bi-weekly. Both IVIG and SCIG effectively raise IgG levels to fight infections, with the choice of administration route depending on individual patient needs and preferences.