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 complex with free virions, preventing their adhesion to the epithelium. Second, since IgA is actively transported by the polymeric immunoglobulin receptor (pIgR) through epithelial cells into the mucosal secretions, IgA may be able to interrupt virus production within infected epithelial cells by binding to newly synthesized viral proteins. Finally, since mucosal immunoglobulins are produced by plasma cells in the lamina propria, IgA antibodies, via the pIgR, can potentially shuttle viral antigens released from epithelial cells back into the mucosal secretions.