MECHANISMS OF INACTIVATION OF RESPIRATORY VIRUSES BY IGA, INCLUDING INTRAEPITHELIAL NEUTRALIZATION

IgA is thought to provide three levels of anti-viral protection in the respiratory and other mucous membranes. First, IgA antibodies can com plex with free virions, preventing their adhesion to the epithelium. S econd, since IgA is actively transported by the polymeric immunoglobul in receptor (pIgR) through epithelial cells into the mucosal secretion s, IgA may be able to interrupt virus production within infected epith elial cells by binding to newly synthesized viral proteins. Finally, s ince mucosal immunoglobulins are produced by plasma cells in the lamin a propria, IgA antibodies, via the pIgR, can potentially shuttle viral antigens released from epithelial cells back into the mucosal secreti ons.