Secretory immunoglobulin A: autoantibody activity in gastric juice.

An immunoglobulin A of the secretory variety, present in the gastric juice of a patient with pernicious anemia, was shown to have specificity for intrinsic factor. This is the first demonstration in gastric juice of antibody activity restricted to secretory IgA; further, this is the first example of an exocrine (gastric) immune system producing an autoantibody specifically directed toward a product synthesized by that same exocrine organ.