SPECIFICITIES OF ANTINEUTROPHIL AUTOANTIBODIES IN PATIENTS WITH RHEUMATOID-ARTHRITIS (RA)

The objective of this study was to characterize antigens recognized by neutrophil-specific autoantibodies from patients with RA. Sera from 6 2 RA patients were screened by indirect immunofluorescence (IIF). Posi tive sera were further tested by ELISAs for antibodies against various granule proteins and by immunoblotting of electrophoretically separat ed cell, granule or nuclear extracts. Forty-two sera (68%) reacted wit h ethanol-fixed neutrophils. In the ELISAs 32% of the 28 medium to str ongly IIF-positive sera were negative, while 43% were weakly positive for more than one antigen. Immunoblots of whole neutrophils showed IgG reactions at 25-35 kD, in the 55-kD region, at 80 kD, and at 110 kD. Most sera reacted with more than one band. Except for the 55-kD antige n, none of the antigens appeared in lymphocytes. The most notable reac tivity in subcellular fractions was with lactoferrin and with bands of 25-35 kD from nuclei. In conclusion, anti-neutrophil autoantibodies f rom RA patients recognize different antigens in the cytoplasm and in t he nucleus. Lactoferrin is one of the common antigens recognized, but also unknown nuclear antigens of 25-35 kD mel, wt are involved.