immunoglobulin G

Immunoglobulin G (IgG) is a type of antibody—a protein that the immune system produces to fight off infections. It is the most abundant antibody in the blood and plays a key role in recognizing and neutralizing bacteria, viruses, and other harmful substances. IgG can also provide long-term immunity after an infection or vaccination, "remembering" past invaders so the body can respond quickly if they appear again. Its presence is often measured in blood tests to assess immune health or exposure to specific diseases.