Showing papers by "Antonella Capozzi published in 2007"

Anti-β2-glycoprotein I antibodies induce monocyte release of tumor necrosis factor α and tissue factor by signal transduction pathways involving lipid rafts

Abstract: Objective To investigate the association of β2-glycoprotein I (β2GPI) with lipid rafts in monocytic cells and to evaluate the proinflammatory and procoagulant effects of anti-β2GPI binding to its target antigen on the monocyte plasma membrane. Methods Human monocytes were fractionated by sucrose density-gradient centrifugation and analyzed by Western blotting. Immunoprecipitation experiments were performed to analyze the association of β2GPI with lipid rafts and the possible interaction of β2GPI with annexin A2 and Toll-like receptor 4 (TLR-4). Monocytes were then stimulated with affinity-purified anti-β2GPI antibodies from patients with the antiphospholipid syndrome (APS). Interleukin-1 receptor–associated kinase (IRAK) phosphorylation and NF-κB activation were evaluated by immunoprecipitation and transcription factor assay, respectively. Supernatants from monocytes were tested for tumor necrosis factor α (TNFα) and tissue factor (TF) levels by enzyme-linked immunosorbent assay. Results We found β2GPI and its putative receptor annexin A2 in lipid raft fractions of human monocytes. Moreover, there was an association between β2GPI and TLR-4, suggesting that it was partially dependent on raft integrity. Triggering with anti-β2GPI antibodies induced IRAK phosphorylation and consequent NF-κB activation, which led to the release of TNFα and TF. Conclusion Anti-β2GPI antibodies react with their target antigen, likely in association with annexin A2 and TLR-4, in lipid rafts in the monocyte plasma membrane. Anti-β2GPI binding triggers IRAK phosphorylation and NF-κB translocation, leading to a proinflammatory and procoagulant monocyte phenotype characterized by the release of TNFα and TF, respectively. These findings provide new insight into the pathogenesis of APS, improving our knowledge of valuable therapeutic targets.

Screening of endothelial expression libraries for the identification of novel autoantigens involved in distinct autoimmune diseases characterized by endothelial dysfunction

Abstract: Screening a cDNA expression library is a powerful technique that allows identification of previously uncharacterized antigens. Proteins recognized by antibodies from patients with autoimmune diseases have been intensively studied over the past two decades since cDNAs encoding autoantigens have become available. Identity of many of them has been defined, and specific structural motifs or post-translational modifications, which may be important to explain the generation of such antibodies during the autoimmune process, have been pointed out. The screening of human umbilical artery or microvascular endothelial cell expression libraries appears to be a useful tool for the characterization of endothelial autoantigens allowing us to identify several molecules recognized from serum anti-endothelial cell antibodies of patients with diseases characterized by immune-mediated endothelial dysfunctions.