Critical role of TLR2 and TLR4 in autoantibody production and glomerulonephritis in lpr mutation-induced mouse lupus.

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by pathogenic autoantibodies directed against nuclear Ags and immune complex deposits in damaged organs. Environmental factors have been thought to play a role in the onset of the disease. The recognition of these factors is mediated by TLRs, in particular TLR2 and TLR4 which bind pathogen-associated molecular patterns of Gram(+) and Gram(-) bacteria, respectively. We attempted to determine the role of these TLRs in SLE by creating TLR2- or TLR4-deficient C57BL/6(lpr/lpr) mice. These mice developed a less severe disease and fewer immunological alterations. Indeed, in C57BL/6(lpr/lpr)-TLR2 or -TLR4-deficient mice, glomerular IgG deposits and mesangial cell proliferation were dramatically decreased and antinuclear, anti-dsDNA, and anti-cardiolipin autoantibody titers were significantly reduced. However, the response against nucleosome remained unaffected, indicating a role of TLR2 and TLR4 in the production of Abs directed against only certain categories of SLE-related autoantigens. Analysis of B cell phenotype showed a significant reduction of marginal zone B cells, particularly in C57BL/6(lpr/lpr)-TLR4-deficient mice, suggesting an important role of TLR4 in the sustained activation of these cells likely involved in autoantibody production. Interestingly, the lack of TLR4 also affected the production of cytokines involved in the development of lupus disease.

Detection and characterization of anti-envoplakin linker autoantibodies in paraneoplastic pemphigus using specific bead-based assay.

Paraneoplastic pemphigus (PNP) is characterized by an autoantibody response directed against desmosomal antigens, desmogleins and plakin's proteins, i.e., periplakin and envoplakin. Notably, PNP antibodies were shown to recognize major epitopes located in the linker subdomain of human envoplakin and thus, may constitute a diagnostic marker of PNP. In this study, a recombinant envoplakin-linker subdomain (rENV-L) was produced and used to develop a specific bead-based assay to determine the prevalence and titers of anti-rENV-L antibodies in patients with different types of autoimmune bullous skin diseases. Sera from 33 PNP, 41 pemphigus vulgaris, 46 pemphigus foliaceus, 24 bullous pemphigoid and 74 normal subjects were analyzed by rENV-L bead-based assay: 23/33 (69.7%) PNP, 2/24 (8.3%) bullous pemphigoid and 4/74 (5.4%) healthy control sera showed IgG reactivity against rENV-L. For PNP, the sensitivity and specificity of the assay were 69.7% and 94.6%, respectively. Among the PNP sera reacting with envoplakin and periplakin by immunoblot analysis, 80.8% contained anti-rENV-L antibodies. Finally, we showed that an anti-rENV-L mAb that recognizes both envoplakin and periplakin gave the same fluorescence pattern on rat bladder sections than PNP sera. Thus, anti-rENV-L antibodies constitute a useful diagnostic marker of PNP and our bead-based assay, notably combined with other epidermal autoantigens, a useful tool to diagnose PNP.

Role of TLR9 in anti-nucleosome and anti-DNA antibody production in lpr mutation-induced murine lupus.

Systemic lupus erythematosus is characterized by the production of autoantibodies directed against nuclear Ags, including nucleosome and DNA. TLR9 is thought to play a role in the production of these autoantibodies through the capacity of nuclear immunogenic particles to interact both with BCR and TLR9. To determine the role of TLR9 in SLE, C57BL/6-lpr/lpr-TLR9(-/-) and TLR9(+/+) mice were analyzed. The abrogation of TLR9 totally impaired the production of anti-nucleosome Abs, whereas no difference was observed in the frequency of anti-dsDNA autoantibodies whose titer was strikingly higher in TLR9(-/-) mice. In addition a higher rate of mesangial proliferation was observed in the kidney of TLR9-deficient animals. These results indicate that in C57BL/6-lpr/lpr mice, TLR9 is absolutely required for the anti-nucleosome Ab response but not for anti-dsDNA Ab production which is involved in mesangial proliferation.

Association between anti-nucleophosmin and anti-cardiolipin antibodies in (NZW x BXSB)F1 mice and human systemic lupus erythematosus.

We showed previously that nucleophosmin (NPM), a nucleolar phosphoprotein, is recognized by sera from (NZW x BXSB)F1 (WB) mice, a model of systemic lupus erythematosus (SLE) and anti-phospholipid syndrome. In the present study we analysed the prevalence and kinetics of anti-NPM autoantibodies in WB mice by a solid-phase ELISA with recombinant human (rh) NPM as the antigen and showed that most male WB mouse sera had anti-NPM antibodies that were responsible for their indirect immunofluorescence staining pattern on Hep-2 cells. Anti-NPM antibodies were significantly associated with anti-cardiolipin (aCL) antibodies. This antibody profile mirrored that observed in certain human SLE sera because anti-NPM antibodies were detected in 28% of the sera from patients with SLE and were similarly associated with aCL antibodies. The demonstration that rhNPM bound to cardiolipin (CL) in vitro and increased the CL-binding activity of a WB-derived aCL monoclonal antibody indicates that NPM can interact with CL to form SLE-related immunogenic particles that might be responsible for the concomitant production of anti-NPM and aCL antibodies.