OverviewThe antibody level in the blood is a reflection of the body's past experience or exposure to an antigen, or something that the body does not recognize as self. Every living cell has different protein markers on its surface called antigens, and the body's immune system identifies those cells that are not part of its structure by those surface proteins.
Update Date 5/18/2014
Updated by: Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School, Washington, DC. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.