Gastric autoimmunity in pernicious anemia.

Abstract The finding of a secretory IgA autoantibody to intrinsic factor in the gastric juice of a patient with pernicious anemia prompted this investigation. Saliva and serum from this subject were studied to determine whether the secretory IgA autoantibody was of salivary origin and whether the IgA component of the gastric antibody was selectively transported from serum into gastric juice. The serum contained both blocking and binding autoantibodies to intrinsic factor restricted to the IgG class of immunoglobulins; the serum binding antibody had both kappa and lambda light chains. Antibody activity was not detected in the patient's saliva. The immunologic differences between the secretory IgA autoantibody in gastric juice and the IgG autoantibody in serum indicate that they are products of different immune systems. These data strongly suggest that the gastric secretory IgA autoantibody to intrinsic factor was produced by immunologically competent cells of the gastric immune system. This observation establishes the concept of gastric autoimmunity in pernicious anemia.