OCCURRENCE OF AUTOANTIBODIES AGAINST INTRINSIC-FACTOR, H,K-ATPASE, AND PEPSINOGEN IN ATROPHIC GASTRITIS AND RHEUMATOID-ARTHRITIS

The occurrence of autoantibodies against intrinsic factor, H,K-ATPase, and pepsinogen was analysed by means of enzyme-linked immunosorbent assay in three groups of sera. Group 1 comprised sera from 14 rheumatoid arthritis patients with normal acid secretion; group 2, sera from 18 rheumatoid arthritis patients with reduced acid secretion; and group 3, sera from 11 patients with pernicious anaemia or achylia. Groups 1 and 2 were rheumatoid factor-positive, and group 3 was negative. Intrinsic factor autoantibodies were low in groups 1 and 2. In group 3, 9 of the 11 sera (82%) scored positive. The highest titres of H,K-ATPase and pepsinogen autoantibodies were found in groups 2 and 3. Only one serum in group 1 scored positive against H,K-ATPase, and two against pepsinogen, whereas corresponding values were 11 (61%) and 7 (39%) in group 2, and 10 (91%) and 6 (55%) in group 3. Autoantibodies against H,K-ATPase from a pool of patient sera recognized both the alpha- and beta-subunits of the enzyme. The present results support the hypothesis of an autoimmune disease overlap between non-organ-specific rheumatoid arthritis and organ-specific pernicious anaemia.