IgG (Serum)

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.