Abstract 5515: Proteomics, Metabolomics and Immunomics on Human Microparticles Derived from Atherosclerotic Plaques
Background. Microparticles (MPs) with procoagulant activity are present in human atherosclerosis, but no detailed information is available on their protein and metabolite composition.
Methods and Results. In this study, we performed a combined proteomic, metabolomic and immunomic analysis to obtain insights into the role of MPs in atherogenesis. MP proteins were identified by tandem mass spectrometry, metabolite profiles were determined by high-resolution NMR spectroscopy and antibody reactivity was assessed against combinatorial antigen libraries. The proteomic analysis resulted in the identification of 151 unique proteins in MPs, including surface antigens consistent with their leukocyte origin, ie. CD14, CD11c, CD18, CD29, CD51, CD36 and major histocompatibility complex class I and II. Moreover, MPs had metabolite profiles, which were distinct from atherosclerotic plaques. When proteins on the MP surface were fluorescence tagged and separated by 2-dimensional gel electrophoresis, immunoglobulins were not surface-labeled. Subsequent flow cytometry analysis on perme-abilized and non-permeabilized plaque MPs confirmed that immunoglobulins were trapped inside plaque-derived MPs. Notably, co-labelling for CD14 and IgG revealed that over 90% of the IgG containing MPs were CD14 positive, indicating a macrophage origin. Screening against a combinatorial antigen library revealed that the immunologic profiles of antibodies in MPs were similar to those found in plaques, but differed profoundly from antibodies in plasma and unexpectedly, showed strong reactions with oligosaccharide antigens, in particular blood group antigen A and the Gal-alpha-(1,3)-Gal linkage, the antigen responsible for hyperacute rejection in xenotransplantation.
Conclusions. This study provides the first evidence that immune complexes in human atherosclerotic lesions exist within MPs derived from plaque macrophages, that their portfolio is different from circulating antibodies in plasma and that common carbohydrates are important antigens in atherosclerosis. Thus, besides being a determinant of plaque thrombogenicity, MPs might play a previously unrecognized role in the containment of immune complexes, which is likely to influence plaque stability.