Immunoglobulins Panel, Serum

Immunoglobulin A (IgA) is a major antibody isotype found predominantly in mucosal secretions (e.g., saliva, tears, respiratory and gastrointestinal mucus) and also in serum. It plays a critical role in mucosal immunity, providing the first line of defense against inhaled and ingested pathogens. Serum IgA levels can be affected by various conditions. Selective IgA deficiency is the most common primary immunodeficiency.

Immunoglobulin G (IgG) is the most abundant antibody in blood and extracellular fluid, crucial for long-term immunity against bacteria, viruses, and toxins. It is produced during secondary immune responses. Low levels (hypogammaglobulinemia) increase infection susceptibility, while high levels (hypergammaglobulinemia) can indicate chronic infection, autoimmune disease, or IgG myeloma.

Immunoglobulin M (IgM) is the largest antibody and is the first to be synthesized by B cells in response to an initial (primary) exposure to an antigen. It plays a crucial role in early immune defense, particularly against bacterial and viral infections. Elevated IgM can indicate a recent or ongoing infection, Waldenström's macroglobulinemia (a type of lymphoma producing monoclonal IgM), or certain autoimmune conditions like primary biliary cholangitis. Low levels can suggest an immunodeficiency.