Plasma cells, also called plasma B cells or effector B cells, are white blood cells that originate in the lymphoid organs as B cells and secrete large quantities of proteins called antibodies in response to being presented specific substances called antigens. These antibodies are transported from the plasma cells by the blood plasma and the lymphatic system to the site of the target antigen, where they initiate its neutralization or destruction. B cells differentiate into plasma cells that produce antibody molecules closely modeled after the receptors of the precursor B cell.

Immunoglobulin G (IgG) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG antibody has two paratopes.