Standardization of autoantibody testing : a paradigm for serology in rheumatic diseases

Autoantibody measurement is an excellent tool to confirm the diagnosis of rheumatic autoimmune diseases. Hence, reliability and harmonization of autoantibody testing are essential, but these issues are still a matter of debate. Intrinsic variability in analytes and reagents as well as heterogeneity of the techniques are the main reasons for discrepancies in inter-laboratory variations and reporting of test results. This lack of reliability might be responsible for wrong or missed diagnoses, as well as additional costs due to assay repetition, unnecessary use of confirmatory tests and/or consequent diagnostic investigations. To overcome such issues, the standardization of autoantibody testing requires efforts on all aspects of the assays, including the definition of the analyte, the pre-analytical stages, the calibration method and the reporting of results. As part of such efforts, the availability of suitable reference materials for calibration and quality control would enable the development of a reliable reference system. Strong-positive sera from patients have been used as reference materials in most of the autoantibody assays for rheumatic diseases; however, antigen-affinity-purified immunoglobulin fractions or in some cases reliable monoclonal antibody preparations offer more adequate tools for standardization. Systematic assessments of reference materials are currently underway, and preliminary results appear to be encouraging

Antiphospholipid antibodies and the antiphospholipid syndrome : pathogenic mechanisms

Antiphospholipid antibodies (Abs) are associated with thrombosis and are a risk factor for recurrent pregnancy loss and obstetric complications in patients with the antiphospholipid syndrome. It is generally accepted that the major autoantigen for aPL Abs is \u3b22 glycoprotein I, which mediates the binding of aPL Abs to target cells (i.e., endothelial cells, monocytes, platelets, trophoblasts, etc.) leading to thrombosis and fetal loss. This article addresses molecular events triggered by aPL Abs on endothelial cells, platelets, and monocytes and complement activation, as well as a review of the current knowledge with regard to the putative receptor(s) recognized by aPL Abs on target cells as well as novel mechanisms that involve fibrinolytic processes. A section is devoted to the description of thrombotic and inflammatory processes that lead to obstetric complications mediated by aPL Abs. Based on experimental evidence using in vitro and in vivo models, new targeted therapies for treatment and/or prevention of thrombosis and pregnancy loss in antiphospholipid syndrome are proposed. Copyrigh

Changes in regulation of human monocyte proteins in response to IgG from patients with antiphospholipid syndrome

The effects of IgG from patients with the antiphospholipid syndrome (APS) upon monocyte activation have not been fully characterised. We carried out a comprehensive proteomic analysis of human monocytes treated with IgG from patients with different manifestations of the APS. Using differential gel electrophoresis (2D DiGE) four of the most significantly regulated proteins: - vimentin (VIM); zinc finger CCH domain containing protein 18; CAP Gly domain containing linker protein 2; and myeloperoxidase - were differentially regulated in monocytes treated with thrombotic or obstetric APS-IgG, compared with healthy control (HC)-IgG. These findings were confirmed by comparing monocytes isolated from APS patients and HC. Anti-VIM antibodies (AVA) were significantly increased in 11 of 27 (40.7%) patients with APS. VIM expression on HC monocytes was stimulated more strongly by APS-IgG from patients with higher avidity serum AVA. We further characterised the proteome of thrombotic APS-IgG treated-monocytes using a label-free proteomics technique. Of 12 proteins identified with the most confidence, two overlapped with 2D DiGE and many possessed immune response, cytoskeletal, coagulation and signal transduction functions which are all relevant to APS and may therefore provide potential new therapeutic targets of this disease