C2 Plasma-derived immunoglobulins

When the human body is invaded by foreign organisms it defends itself either through the propagation of a cellular response (cell-mediated immunity) or by the production of soluble proteins. This production of soluble proteins is known as humoral immunity, so-called because it refers to substances found within the humours, or body fluids. While there are a number of components that have been identified as important in the humoral immune response, including complement proteins [1], the key molecules necessary for mediating specific humoral immunity are immunoglobulins (Ig), also known as antibodies (Ab) (see also chapter A3).