Characterization of Human Autoantibodies Reactive to Gastric Parietal Cells

Human sera from autoimmune gastritis patients containing autoantibodies to gastric parietal cells were analyzed by immunological methods. Enzyme linked immuno-sorbent assay demonstrated that all nine sera reacted with pig gastric vesicles enriched in H⁺/K⁺-ATPase (gastric proton pump). Immunoblotting experiments indicated that the a subunit of the H⁺/K⁺-ATPase was the major antigen in the vesicles with two of the sera reacting strongly. We further characterized the specificitiy of the antibodies using partial sequences of the pig α subunit fused with truncated TrpE (anthranilate synthase). The antibodies from autoimmune gastritis patients reacted differently to the two fusion proteins (Met-1 to Ala-79, and Arg-606 to Ile-964), indicating that each patient sera contains a mixture of autoantibodies recognizing different epitopes with variable contents.