The structure of IgA

It is a surprising and often overlooked fact that the majority of the body's immunoglobulin (Ig) production is geared toward the IgA class. Indeed, the daily synthesis of IgA far outstretches the combined production of all the other Ig classes. Most IgA is produced in mucosa-associated tissue by large numbers of plasma cells in the mucosal subepithelium (Conley and Delacroix, 1987; Mestecky et al., 1991). The necessity for such intensive IgA production at the mucosa presumably reflects a critical requirement, at least in evolutionary terms, for immune protection of mucosal sites. The mucosal surfaces collectively have a huge surface area (∼400 m2 in the human adult) (Childers et al., 1989). They represent, by far, the largest area of contact between the immune system and the environment and can be considered an important point of exposure to inhaled and ingested pathogens.