Immunoglobulin G (IgG) is a type of antibody, a protein produced by the immune system. These antibodies are essential for protecting the body from foreign invaders like bacteria and viruses. IgG plays a significant role in the body’s defense mechanisms, and its levels in the blood can provide insights into immune system activity.
What Immunoglobulin G Is
Immunoglobulin G (IgG) is the most abundant antibody in human blood, comprising about 75% of all serum antibodies. These Y-shaped proteins are created by plasma B cells, a type of white blood cell. IgG circulates throughout the blood and other extracellular fluids, reaching various body tissues.
IgG antibodies are crucial for long-term immunity, primarily involved in the secondary immune response. After initial pathogen exposure, the immune system “remembers” it, producing IgG antibodies to quickly neutralize or eliminate the threat upon subsequent encounters. They protect the body by binding to pathogens, preventing cell entry, marking them for destruction by other immune cells, and activating other immune responses. IgG is also unique as the only antibody that can cross the placenta, providing immune protection to a developing fetus.
Understanding Elevated IgG
When a blood test indicates elevated IgG levels, it generally signifies an active immune response within the body. IgG levels are a marker reflecting immune system activity, not a diagnosis on their own. The body produces more IgG when actively fighting an infection, experiencing inflammation, or responding to certain medical conditions.
A deviation above normal IgG ranges suggests the immune system has been stimulated to produce more protective antibodies. This elevation indicates the body is addressing a recent or ongoing immune challenge.
Common Causes of High IgG
Elevated IgG levels can stem from various underlying medical conditions and physiological states.
Infections
Acute and chronic infections are common causes. The body produces IgG antibodies to combat a wide range of pathogens, including viruses (e.g., mononucleosis, hepatitis), bacteria, parasites, or fungi. These antibodies target and help clear invading microorganisms.
Autoimmune Diseases
Autoimmune diseases also commonly lead to increased IgG levels. In conditions like lupus, rheumatoid arthritis, Sjögren’s syndrome, or multiple sclerosis, the immune system mistakenly attacks the body’s own healthy tissues. This misguided activity triggers inflammation and ongoing antibody production as the body attempts to fight what it perceives as a threat.
Chronic Inflammatory Conditions
Chronic inflammatory conditions, such as inflammatory bowel disease (Crohn’s disease or ulcerative colitis) and chronic liver diseases, can also result in elevated IgG. Persistent inflammation signals a continuous immune response, prompting increased IgG production to manage the inflammatory process and protect affected tissues.
Cancers
Certain cancers, specifically plasma cell dyscrasias like multiple myeloma or monoclonal gammopathy of undetermined significance (MGUS), cause a rise in IgG. These involve uncontrolled proliferation of plasma cells that produce an excessive type of immunoglobulin, often IgG, leading to a monoclonal spike.
Less common causes for elevated IgG include sarcoidosis, an inflammatory disease affecting multiple organs, or certain kidney diseases, where immune system dysregulation or chronic inflammation can contribute to higher antibody concentrations.
What to Do Next
Discovering elevated IgG levels in a blood test warrants further medical evaluation. Consult a healthcare professional who can interpret the results in the context of your overall health, symptoms, and medical history. They will provide a comprehensive assessment and determine the significance of the elevated levels.
Additional diagnostic tests are often necessary to identify the specific reason for increased IgG. These may include further blood work, imaging studies, or other specialized evaluations, depending on the suspected cause. Self-diagnosis or self-treatment based solely on an elevated IgG result is not recommended, as interpreting and managing such findings requires professional medical expertise.