Participation of histones and ubiquitin in lupus nephritis

To evaluate the role of histones and ubiquitin in lupus nephritis, we searched for glomerular deposits of histones and ubiquitin in renal biopsy specimens from 53 patients with systemic lupus erythematosus (SLE) and 30 with non-lupus glomerulonephritis. Glomerular immunofluorescence staining revealed positive for histone H2A, H1 + H3, H4 and ubiquitin in 49.1% (26/53), 45.3% (24/53), 32.1% (17/53) and 22.6% (12/53) of the SLE patients, respectively. Non-SLE renal biopsies revealed absence of positive staining with histone H2A, H1 + H3, H4 and ubiquitin. The positive incidence of histone H1 + H3 and ubiquitin in diffuse proliferative lupus nephritis was significantly different (p < 0.01) from that in minor glomerular abnormality. Levels of CH50 in patients with glomerular deposition of histone H1 + H3 (p < 0.001) and ubiquitin (p < 0.01) were significantly lower than in patients without deposition. Levels of anti-DNA antibody in patients with glomerular deposition of histone H1 + H3 were significantly higher than in patients without deposition (p < 0.05). Only the positive incidence of glomerular deposition of ubiquitin was correlated with the histological activity index (p < 0.05). These results suggest that histones and ubiquitin may play an important role in the induction of lupus nephritis.