IGA AND MUCOSAL DEFENSE

The traditional role of IgA antibodies in mucosal defense has been con sidered as providing an immune barrier to keep exogenous substances, i ncluding microbial pathogens, from penetrating the mucosa. In this way infections can be prevented. More recently, studies in vitro and in v ivo are providing evidence to suggest that IgA may have additional rol es in mucosal defense. For example, during their passage through the l ining epithelial cells of mucous membranes en route to the secretions, IgA antibodies may have an opportunity to neutralize intracellular pa thogens like viruses. Also, IgA antibodies in the mucosal lamina propr ia have opportunities to complex with antigens and excrete them throug h the adjacent mucosal epithelium, again by the same route to the secr etions that is taken by free IgA. These latter functions could aid in recovery from infection.