Immunoglobulin G (Ig G)
Like other antibodies, immunoglobulin G is produced from B cells or plasma cells (a class of lymphocytes) of the bone marrow. It is the most abundant antibody isotype in the body, making up about 75 percent of the total immunoglobulins. For this reason, it forms a major part of the humoral immune response. And due to its small size, immunoglobulin G can easily diffuse in the extracellular fluid (or blood) and bind to the antigen or receptor as the case may be. Ig G is unique in that it is the only immunoglobulin that crosses the feto-maternal barrier through the placenta. It offers passive immunity to the fetus. [1]
