American Journal of Clinical Nutrition, Vol 25, 1344-1350, Copyright © 1972 by The American Society for Clinical Nutrition, Inc.

A review of secretory immune mechanisms

¹ From the Department of Medicine, State University of New York at Buffalo, E. J. Meyer Memorial Hospital, 462 Grider Street, Buffalo, New York 14215

Immunoglobulins, particularly those of the IgA class, are widely distributed in mammalian body fluids elaborated by the intestine, breast, salivary gland, bronchopulmonary mucosa, and other secretions exposed to antigens in the external environment. To a considerable extent, these antibody proteins are elaborated by the mucus membrane through a cooperative process involving the epithelial cell and the local immunocompetent plasma cells and lymphocytes. Subclasses of IgA have recently been identified, and secretory IgA contains J chain, a newly recognized structural component characteristic of polymeric immunoglobulins. Antibodies directed against viruses, bacteria and non-replicating antigens can readily be demonstrated in secretions, but their precise role in overall defense against disease has not been fully established, particularly in the case of bacterial infections. The capacity of IgA to activate complement components by the newly described alternate pathway or complement "shunt" mechanism may provide insight into some of the biological properties of the secretory system.