Fumio Osakada

Prevalence and characterization of perinuclear anti-neutrophil cytoplasmic antibodies (P-ANCA) directed against HMG1 and HMG2 in ulcerative colitis (UC)

In a previous study, we reported that the high mobility group (HMG) non‐histone chromosomal proteins HMG1 and HMG2 were novel target antigens of P‐ANCA. In this study, we determined the immunodiagnostic value of anti‐HMG1/HMG2 antibodies in patients with UC. Sixty sera from patients with UC were tested for reactivity with HMG1 and HMG2 by means of ELISA. Anti‐HMG1 antibody was detected in 32% of patients (40% of P‐ANCA+ patients). Anti‐HMG2 antibody was detected in 33% (40% of P‐ANCA+ patients). Thirty‐five percent of sera were positive for antibody to either HMG1 or HMG2 (43% of P‐ANCA+ patients). P‐ANCA+ patients expressed anti‐HMG1/HMG2 antibodies with significantly greater frequency compared with P‐ANCA− patients. Furthermore, the anti‐HMG1/HMG2 antibodies were significantly related to disease activity in UC. Sixteen of the 18 UC patients, who had high titres of anti‐HMG1 or ‐HMG2 antibody during the active phase, showed lower titres in the inactive phase. Anti‐HMG1/HMG2 antibodies appear to be useful as a marker for disease activity in UC.

High mobility group (HMG) non-histone chromosomal proteins HMG1 and HMG2 are significant target antigens of perinuclear anti-neutrophil cytoplasmic antibodies in autoimmune hepatitis

BACKGROUND High mobility group (HMG) non-histone chromosomal proteins HMG1 and HMG2 have been identified as novel antigens of perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCAs), and the existence of anti-HMG1 and anti-HMG2 antibodies in a population of patients with ulcerative colitis has been reported. AIMS To investigate whether HMG1 and HMG2 are target antigens for p-ANCAs in autoimmune hepatitis (AIH). PATIENTS Serum samples from 28 patients with AIH, 44 patients with primary biliary cirrhosis (PBC), 27 patients with chronic hepatitis C, and 23 patients with chronic hepatitis B were tested. METHODS ANCAs were detected by routine indirect immunofluorescence (IIF). Anti-HMG1 and anti-HMG2 antibodies were assayed by enzyme linked immunosorbent assay. RESULTS p-ANCAs were detected in 89% (25/28) of patients with AIH, 36% (16/44) of patients with PBC, 11% (3/27) of patients with chronic hepatitis C, and 13% (3/23) of patients with chronic hepatitis B. Anti-HMG1 and/or anti-HMG2 antibodies were detected in 89% (25/28) of patients with AIH, 70% (31/44) with PBC, 26% (7/27) with chronic hepatitis C, and 9% (2/23) with chronic hepatitis B. In AIH, anti-HMG1 and/or anti-HMG2 antibodies were detected in 96% (24/25) of p-ANCA positive patients. The p-ANCA staining pattern detected by IIF using sera from patients with AIH disappeared or decreased in titre after preincubation with a mixture of HMG1/HMG2. The presence and titres of those antibodies in AIH correlated significantly with those of p-ANCA, but not with those of anti-nuclear antibody or anti-smooth muscle antibody. CONCLUSIONS HMG1 and HMG2 are significant target antigens of p-ANCA in AIH.

Cloning of novel soluble gp130 and detection of its neutralizing autoantibodies in rheumatoid arthritis

In an attempt to isolate disease-associated autoantigens in rheumatoid arthritis (RA), we cloned a new autoantigen named gp130-RAPS, which is a novel soluble form of the IL-6 signal-transducing molecule gp130. gp130-RAPS is a 50-kDa protein translated from alternatively spliced mRNA and has a truncated form of gp130 with a unique sequence, Asn-Ile-Ala-Ser-Phe (NIASF), in its COOH-terminus. We observed serum antibodies to this NIASF sequence frequently in patients with RA, but not in those with other systemic rheumatic diseases or in healthy subjects. In RA, detection of those antibodies was significantly associated with disease activity indices such as serum C-reactive protein (CRP) levels, erythrocyte sedimentation rate, blood platelet counts, and serum IL-6 concentration. In vitro experiments revealed that gp130-RAPS inhibited IL-6 activity, and this inhibition was neutralized by antibodies to the COOH-terminus of gp130-RAPS derived from patients with RA. Thus, autoantibody to gp130-RAPS may play an important role in the progression of RA by promoting IL-6 activity. Inspection of autoantibodies to gp130-RAPS may become a practical clinical test for RA. gp130-RAPS and its autoantibody provide a new clue to the complicated pathogenesis of RA.

Detection of Anti-Neutrophil Cytoplasmic Antibodies in MRL/Mp-lpr/lpr Mice and Analysis of their Target Antigens

Anti-neutrophil cytoplasmic antibodies (ANCA) have been widely studied and recognized to be clinically very important for some human diseases including systemic rheumatic diseases. We analyzed ANCA response and their target antigens in MRL/Mp-lpr/lpr (MRL-lpr) mice, an animal model of systemic rheumatic disease. P-ANCA was detected in 57% of the mice. Antibodies to the known P-ANCA target antigens at the same age were examined. Among these, antibodies to high mobility group (HMG) proteins HMG1 and HMG2 were detected in 57% of the mice, 75% of which were also positive for P-ANCA. These anti-HMGl/HMG2 activities were absorbed by preincubation with a mixture of HMG1 and HMG2. In contrast, antibodies to myeloperoxidase and cathepsin G were detected in 14% and 7%, respectively, but these activities were not inhibited by preincubation with corresponding antigens. In addition, the titers of P-ANCA and anti-HMGl/HMG2 antibodies in MRL-lpr mice were significantly correlated with each other. Thus, HMG1 and HMG2 were considered to be significant target antigens of P-ANCA in MRL-lpr mice