Serum or Plasma Concentration of Immunoglobulin G (IgG) Subclass 1 (IgG1)

What Is IgG1 and Its Role in Your Immune System?

IgG1 is one of the four main subclasses of Immunoglobulin G (IgG), the most abundant antibody in your blood. It plays a key role in defending against bacterial and viral infections by binding to pathogens and signaling immune cells to eliminate them. IgG1 is particularly important in early immune responses and long-term immunity.

When Might This Test Be Ordered?

Your healthcare provider may order an IgG1 test if you have symptoms of an immune-related condition, such as recurrent infections, autoimmune diseases, or if you’re being evaluated for a condition affecting antibody production, like hypogammaglobulinemia.

How Is the Test Performed?

A blood sample is drawn from a vein in your arm. The blood is then processed to measure the concentration of IgG1 in your serum or plasma.

What Do Results Mean?

Results may be compared to reference ranges provided by your lab, but they don’t replace a clinical evaluation. Low IgG1 levels could suggest immune system dysfunction, while high levels might be seen in certain chronic infections or autoimmune conditions.