Antikeratin antibody (AKA) and antiperinuclear factor (APF) are antibodies characteristic for rheumatoid arthritis (RA). Our purpose was to obtain information on the occurrence of APF before the onset of clinical disease and on the occurrence of AKA and APF in cases with false-positive rheumatoid factor (RF) reactions.
AKA and APF were measured with indirect immunofluorescence technique using rat esophagus and buccal mucosa cells, respectively, as antigen source.
Five of 30 preillness specimens from subjects who later developed seropositive RA were positive for AKA and APF, 3 sera were positive for only AKA and 3 for only APF. All the eleven sera positive for AKA or APF were RF positive. Both AKA and APF were detected in 6 of 70 sera from RF positive subjects who did not develop RA within a 10-year followup, 3 sera were positive for only AKA and 3 for only APF.
AKA and APF appear to be linked markers of an immunological process which, in RF positive subjects, predicts the development of clinical arthritis. However, disease manifestations develop in only a proportion of cases.