Immunopathology of rheumatoid arthritis. Antikeratin antibodies precede the clinical disease.

We sought to determine whether circulating antikeratin antibodies (AKA) precede the onset of rheumatoid arthritis (RA). By matching the registers of 2 previous population studies with the registry of patients receiving antirheumatic drugs several years later, pre-illness serum specimens could be obtained from 39 individuals who subsequently developed RA. AKA were assayed with the standard indirect immunofluorescence technique. Ten of 39 serum specimens from individuals who subsequently developed seropositive RA, and 1 of 15 sera from individuals who developed seronegative RA, were positive for IgG-class AKA by immunofluorescence assay. The AKA-positive sera were also positive for rheumatoid factors. The findings focus attention on the role of pre-illness immunologic events in the pathogenesis of RA.