Some Thoughts on the Biologic Role of Immunoglobulin A

Abstract

In this speculative article we have chosen to highlight many unsolved problems regarding immunoglobulin A (IgA). As most available information is based on animal experimentation, the reader is cautioned that some of the ideas expressed have not been tested in humans. We hope that some readers may be stimulated to tes t our speculations so as to improve our knowledge and thereby facilitate better approaches to health care . Recent considerations of mucosal immunology (14) have led us to suggest that the primary role of oligomeric IgA is to clear from the circulation soluble and small particulate materials that have crossed the epithelia of various mucosal surfaces. This hypothesis also offers an explanation for how glandular mucosal tissues , not normally exposed to antigen, may receive antigenic stimulation from distant mu cosal sites (Figure 1). Our model suggests a second evolutionary pressure for the IgA system, which may have been derived from th e first ; that is as a first line of defense (5) at mucosal surfaces. Further, we offer some thoughts on the association between IgA immune complexes and certain human diseases, and speculate on some aspects of the regulation of IgA synthesis itself.