nephritis: correlation with severity of renal histology

The correlation between renal histology and class specific (IgG and IgM) antibodies to double stranded DNA (dsDNA) and single stranded DNA (ssDNA) was studied by enzyme linked immunosorbent assay (ELISA) in 40 untreated patients with systemic lupus erythematosus (SLE). The levels of IgG antibodies to dsDNA were significantly higher in patients with World Health Organisation class IV nephritis than in those with class I, class II, or class III nephritis. IgG antibodies to ssDNA were higher in patients with class IV than in those with class II nephritis. IgG antibodies to dsDNA showed a close correlation with the histological activity score and the amount of electron dense deposit. IgG antibodies to ssDNA showed only a weak correlation with the renal histological activity score. IgM antibodies to dsDNA and IgM antibodies to ssDNA were not correlated with renal histological features. Patients with moderate to severe nephritis had a lower ratio ofIgM antibodies to dsDNA to IgG antibodies to dsDNA than those with mild nephritis. These results indicate that the measurement of IgG antibodies to dsDNA is predictive in evaluating renal histological activity in patients with SLE. (Ann Rheum Dis 1993; 52: 14-20) The First Department of Internal Medicine, Osaka City University Medical School, 1-5-7, Asahimachi, Abeno-ku, Osaka 545, Japan M Okamura Y Kanayama K Amastu N Negoro S Kohda T Takeda T Inoue Correspondence to: Dr Okamura. Accepted for publication 19 August 1992 Antibodies to double stranded DNA (dsDNA) are characteristic of systemic lupus erythematosus (SLE),' 2 and these antibodies have been considered to be the principal factor in the pathogenesis of lupus nephritis.3 ' Many workers have reported a significant correlation between serum titres of antibodies to dsDNA and the severity of the disease, particularly associated with lupus nephritis.' 57 Relatively few studies, however, have examined the correlation between antibodies to dsDNA and the histological severity of lupus nephritis."'0 Although Steinman et al, using a synthetic double stranded copolymer of deoxyadenosine and deoxythymidine to detect antibodies to dsDNA, showed a significant correlation between serum titres of antibodies to dsDNA and renal histological severity,'0 other workers using a conventional dsDNA preparation to detect antibodies to dsDNA, could not confirm this.8 9 An enzyme linked immunosorbent assay (ELISA) for antibodies to dsDNA is a sensitive and specific method for their detection and Amastu, Nobuo Negoro, Shinichi Kohda, measurement," 12 and also for the measurement of antibodies to single stranded DNA (ssDNA). " 13 An ELISA offers the opportunity to measure the different antibody classes and to avoid the measurement of non-specific DNA binding proteins. Using a chromatographically purified and SI nuclease treated dsDNA preparation as the solid phase antigen, we used an ELISA for the measurement of antibodies to dsDNA of the IgG and IgM classes and assessed the correlation between serum levels of antibodies to dsDNA and histological severity in 40 untreated patients with SLE. Although antibodies to ssDNA have been thought to be associated with disease activity in patients with SLE,'4 no study has correlated them with renal histological severity. We have examined this and appraised the significance of each parameter in evaluating renal histological severity in patients with SLE. Patients and methods PATIENTS Serum samples were obtained from 40 patients with a clinical diagnosis of SLE at the First Department of Internal Medicine, Osaka City University Hospital. All patients met the 1982 revised criteria for the classification of SLE.'5 None of the patients had received steroids or immunosuppresssive drugs at the time of collecting the serum samples. The serum samples were stored at 80°C until tested. A renal biopsy sample was taken either at the pretreatment stage (30 patients) or within two weeks of the start of treatment (10 patients). Patients were judged to have clinically active nephritis if they showed the presence of either active urinary sediment, proteinuria (over 500 mg/day), or an increased serum creatinine concentration greater than 124 ,umol/l. DNA PREPARATIONS Double stranded DNA prepared from calf thymus DNA (Sigma) was purified by methylated albumin kieselguhr chromatography16 and S1 nuclease treatment.'7 Single stranded DNA was prepared by heating a 0-1 mg/ml solution of dsDNA in phosphate buffered saline (PBS), pH 7-2, for 15 minutes at 100°C followed by rapid cooling in an ice bath. DOUBLE STRANDED DNA COATED MICROTITRE PLATES Methylated bovine serum albumin (BSA) (10 14 group.bmj.com on June 22, 2017 Published by http://ard.bmj.com/ Downloaded from