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Objective: Anti-double-stranded DNA (anti-dsDNA) antibodies may contribute to the pathogenesis of glomerulonephritis (GN) by cross-reacting with alpha-actinin in murine models and in some patients with systemic lupus erythematosus (SLE). We therefore sought to determine possible disease associations with serologic and clinical features and to characterize this new autoantibody specificity., Methods: One hundred patients with SLE were recruited into this multicenter study, as well as 100 rheumatic disease controls and 2,100 healthy blood donors. Clinical disease was evaluated by the SLE Disease Activity Index (SLEDAI; excluding the anti-DNA component). Anti-dsDNA antibodies were detected by conventional enzyme-linked immunosorbent assay (ELISA) and by a commercial enzyme immunoassay (EIA). Anti-alpha-actinin antibodies were detected by ELISA, and their specificity was confirmed by Western blotting and by indirect immunofluorescence using rat kidney sections and mesangial cells as substrates. Highly positive sera were selected for absorption experiments and were affinity-purified for cross-reactivity studies and measurement of antibody avidity., Results: Sera from 62 of the SLE patients had anti-dsDNA antibodies; 21 of these sera also had anti-alpha-actinin antibodies, as compared with 1 of the 38 sera without anti-dsDNA antibodies. Of the 22 patients with anti-alpha-actinin antibodies, 10 had GN, as compared with 14 of the 78 without anti-alpha-actinin antibodies (P < 0.01). In patients with GN, anti-alpha-actinin, but not anti-dsDNA, antibodies correlated with the SLEDAI score (minus the anti-DNA component) and with treatment. The fraction of serum anti-dsDNA antibodies that cross-reacted with alpha-actinin exhibited high avidity for dsDNA, as determined using a commercial EIA for high-avidity anti-dsDNA antibodies and an in-house conventional ELISA., Conclusion: The alpha-actinin-binding antibodies are significantly associated with GN in SLE. Whether such autoantibodies may anticipate the development of this complication of SLE remains to be verified.

Objective: To determine the effect of excessive production of BAFF on the distribution and function of B cell subsets in patients with primary Sjögren's syndrome (SS)., Methods: The phenotype of B lymphocytes was analyzed by flow cytometry. Differences in the expression level of membrane IgD and CD38 were used to identify B lymphocyte subsets evolving from naive Bm1 through memory Bm5 cells. Based on our finding of a low expression of CD45RA, we sorted Bm2/Bm2' cells to determine the time course of translocation of the CD19 molecule and the B cell receptor into lipid rafts, by confocal microscopy. Serum levels of BAFF were measured by an enzyme-linked immunosorbent assay developed in-house., Results: "Circulating" Bm2/Bm2' cells were expanded in patients with primary SS compared with rheumatic disease controls and with normal controls. In addition, these B cell subsets were functionally abnormal. Prolonged residency of the B cell receptor in lipid rafts in these cells was associated with elevated CD19 expression in B cells, most notably, Bm2 and Bm2' cells, obtained from the patients with primary SS. BAFF levels were higher in the patients than in the normal controls and correlated with the percentage of Bm2/Bm2' cells and their expression of CD19 in primary SS patients. These correlations were confirmed by placing sorted Bm1 or Bm2 cells from normal controls in culture in the presence or absence of BAFF., Conclusion: Bm2/Bm2' cells express more CD19 molecules in primary SS patients than in normal controls. BAFF might participate in this elevated expression of CD19. These patients might be suitable candidates for treatment with BAFF antagonists.