PREVALENCE AND CHARACTERIZATION OF NOVEL PANCA, ANTIBODIES TO THE HIGH-MOBILITY GROUP NONHISTONE CHROMOSOMAL-PROTEINS HMG1 AND KMG2 IN SYSTEMIC RHEUMATIC DISEASES

Objective, To determine the immunodiagnostic value of antibodies to th e high mobility group nonhistone chromosomal proteins HMG1 and HMG2, w hich have been identified as novel target antigens of perinuclear anti neutrophil cytoplasmic antibodies (pANCA), in sera from patients with systemic rheumatic diseases. Methods, Anti-HMG1 or HMG2 antibody was a ssayed by ELISA and Western blotting in sera from patients with system ic rheumatic diseases. These antibodies were analyzed for the relation ship with pANCA detected by indirect immunofluorescence in these disea ses, and with clinical features in rheumatoid arthritis (RA) and syste mic lupus erythematosus (SLE). Results, Anti-HMG1 or HMG2 antibody was frequently detected in sera from patients with RA (48%), SLE (45%), S jogren's syndrome (SS) (44%), and systemic sclerosis (SSc) (41%). In t hese diseases, anti-HMG1 antibody was detected more frequently than an ti-HMG2 antibody. In sera from patients with RA, the positivity for an ti-HMG1 and HMG2 antibodies was significantly correlated with the posi tivity for pANCA (p < 0.0001). Anti-HMG1/HMG2 antibodies were associat ed with some disease activity variables, e.g., erythrocyte sedimentati on rate, C-reactive protein, rheumatoid factor, joint score and hand g rip strength in RA, and CH50, C3, C4, and IgG in SLE. Conclusion, Anti -HMG1/HMG2 antibodies are detected commonly in systemic rheumatic dise ases, particularly in RA, SLE, SS, and SSc. HMG1 and HMG2 seem to be t he significant target antigens of pANCA in RA. These antibodies are si gnificantly associated with disease activity indices in RA and SLE.