[Determination of anti-native DNA antibodies by immunofluorescence on Crithidia luciliae. Correlation between renal involvement and the presence of high-avidity anti-native DNA antibodies in lupic disease].

Low avidity native DNA - anti-native DNA complexes dissociate at alkaline pH and in high molarity solutions. This property was used to modify the indirect immunofluorescence reaction on Crithidia luciliae in order to assay high avidity anti-native DNA antibodies resistant to alkaline and strongly saline solutions. Assays were performed in the sera of 36 patients (31 women and 5 men) with systemic lupus erythematosus (SLE). Seventeen of these patients had histologically significant lupus nephritis (WHO types III, IV and V) and 19 had no renal, urinary or biochemical abnormalities. The mean titer of total anti-native DNA antibodies was similar in both groups, but the titer of high avidity anti-native DNA antibodies was significantly higher in patients with lupus nephritis. The percentage of patients with high avidity antibodies was 87% in the group with renal involvement and 28% in the group with no kidneys involvement. Thus, lupus nephritis should be feared when anti-native DNA antibodies with high dissociation constant are found in the sera of SLE patients.