IgG (H+L)

Immunoglobulin G (IgG) is the most abundant type of antibody found in blood and extracellular fluid. It is secreted by B cells and protects body from various bacterial and viral infections by binding those pathogens. IgG antibody is a 150 kDa tetrameric quaternary structure which contains two identical class γ heavy chains of about 50 kDa and two identical light chains of about 25 kDa. The two heavy chains are linked to each other and to a light chain each by disulfide bonds, resulting in a Y-like shape. In any given immunoglobulin molecule, the two heavy chains and the two light chains are identical, giving an antibody molecule two identical antigen-binding sites and thus the ability to bind simultaneously to two identical structures. Naturally, IgG antibodies are generated following class switching and maturation of the antibody response and thus participate predominantly in the secondary immune response.