[Serological and histological study of lupus nephritis with special reference to anti-SSA antibody]

Systemic lupus erythematosus (SLE) is a disease of unknown etiology in which many organs are damaged by deposition of pathogenic autoantibodies and immune complexes Clinically lupus nephritis occurs about 50% in SLE Many studies revealed the association between autoantibodies and lupus nephritis However, the pathogenetic role of autoantibodies in lupus nephritis remains obscure. To elucidate the pathogenetic role of anti-SSA antibody in lupus nephritis, 32 patients with SLE were evaluated by serological and histological methods. Enzyme-linked immunosorbent assay for anti-SSA antibody was developed for this study. It was confirmed that this assay was specific, did not detect autoantibodies other than anti-SSA antibody. The levels of anti-SSA antibody determined by this assay significantly correlated with the levels determined by double immunodiffusion (p less than 0.01). The level of anti-SSA antibody greater than or equal to 200 units was regarded as positive. The serum levels of antinuclear antibody, anti-DNA antibody, anti-RNP antibody, anti-SSA antibody, anti-SSB antibody, C3, and C4 were also determined. Renal biopsy materials were evaluated according to the WHO criteria, and activity index (AI), chronicity index (CI), and pathologic score (PS) were calculated according to Austin et al. The patients were divided into group A (AI greater than or equal to 4, n = 17) and group B (AI less than or equal to 3, n = 15) The levels of anti-DNA antibody were significantly higher in group A than in group B (p less than 0.05). The frequency of positive anti-SSA antibody in group A (70.6%) was greater than in group B (23.3%) significantly (p less than 0.05). However, there were no differences in the levels of anti-nuclear antibody, anti-DNA antibody, anti-RNP anti-body, anti-SSA antibody, anti-SSB antibody, C3, and C4 between group A and group B. Then these patients were divided into group I (anti-SSA greater than or equal to 200 units, n = 17) and group II (anti-SSA less than 200 units, n = 15). AI and CI were greater than in group I than in group II significantly (p less than 0.05). The frequency of pericarditis in group I (35.3%) was greater than group II (6.7%) (p = 0.061), but the frequencies of the other clinical manifestations were not different. AI was correlated with anti-DNA antibody significantly (p less than 0.01), but there were no correlations between other serological data and parameters.(ABSTRACT TRUNCATED AT 400 WORDS)