ANTIBODIES AGAINST A PEPTIDE SEQUENCE LOCATED IN THE LINKER REGION OFTHE HMG-1 2 BOX DOMAINS IN SERA FROM PATIENTS WITH JUVENILE RHEUMATOID-ARTHRITIS/

Objective. To extend our work on the mapping of B cell epitopes on nuc leosomal high mobility group (HMG) proteins in the sera of patients wi th juvenile rheumatoid arthritis (JRA). Methods. Seventy-seven pauciar ticular-onset JRA serum samples from antinuclear antibody (ANA)positiv e patients and 42 polyarticular-onset JRA patient sera found to react with HMG-2 by immunoblotting were used in this study. To identify B ce ll epitopes on HMG-2, recombinant HMG-2 protein fragments were used in enzyme-linked immunosorbent assay (ELISA) and in competition ELISA ex periments with a set of overlapping synthetic peptides. Fine epitope m apping was achieved by oligopeptide synthesis, followed by immunoblott ing. Results. Pauciarticular, but not polyarticular, JRA patient sera were found to recognize a lysine-rich major epitope (KKGKKKDP), which is located in the linker region of the HMG box domains of the HMG-2 no nhistone chromosomal protein, No significant immunoreactions were obse rved in sera from ANA-negative JRA patients and in sera from children with nonrheumatic diseases, indicating that this epitope seems to be s pecific for pauciarticular-onset JRA. Conclusion. In addition to our p revious finding that JRA sera will react with a defined epitope on HMG -17, pauciarticular JRA patient sera were also found to recognize a de fined epitope on the HMG-2 protein, thus suggesting the importance of this epitope in the etiology of JRA.