Abstract

Antikeratin antibodies reacting in a laminar distribution with keratinised rat oesophagus were found in the sera of a proportion of patients with rheumatoid arthritis but not in healthy controls. In rheumatoid arthritis (RA) the proportion of sera exhibiting this reactivity varied with the site tested in the rat's upper alimentary tract. There were 36.4% of 99 patients with RA who gave positive reactivity to the middle third of the rat oesophagus. This antikeratin reactivity was related to the occurrence of other antitissue antibodies (to reticulin, gastric parietal cells, smooth muscle, mitochondria, or nuclear components) in the same patients with rheumatoid arthritis. It was not related to the duration of early morning stiffness, the Ritchie index, the erythrocyte sedimentation rate, certain acute phase proteins (haptoglobin and C-reactive protein) nor to the levels of haemoglobin or immunoglobulins. Antikeratin antibodies were not specific for rheumatoid arthritis and also occurred in 50% of 16 patients with progressive systemic sclerosis.