Autoantibodies directed against cytoplasmic antigens of neutrophils (ANCA), especially proteinase 3 (PR-3), have proved to be a useful clinical tool confirming the diagnosis or monitoring disease activity of Wegener's granulomatosis (WG). Although several concepts concerning the pathophysiologic potentials of ANCA have been discussed, only sparse data about ANCA-endothelium interactions have been available. In this study, we have investigated the expression of PR-3 in cytokine- treated human endothelial cells using purified anti-PR-3 antibodies of patients with WG, murine and human monoclonal anti-PR-3 antibodies as probes. We were able to show that tumor necrosis factor-alpha, interleukin-1 alpha/beta, and interferon-gamma led to an increased PR-3 expression in the cytoplasm of endothelial cells by performing polymerase chain reaction analysis, Western blot, cyto-enzyme-linked immunosorbent assays, and confocal laser scanning microscopy. Moreover, PR-3 was also translocated into the cell membrane, becoming accessible to ANCA. Our data suggest a possible direct pathogenic effect of anti- PR-3 antibodies in WG and other vasculitides. Anti-PR-3 antibodies represent an important missing link in ANCA-endothelial interactions.

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease of unknown aetiology. Recent studies have shown that genetic factors and both cellular and humoral immunological abnormalities are important in the pathogenesis of PSC. The most prominent autoantibodies in PSC are anti-neutrophil cytoplasmic antibodies (ANCA). The autoepitopes of ANCA in PSC are not well defined. The aim of this study was to identify corresponding ANCA autoantigens in patients with PSC. A biochemical approach with enrichment and partial purification of soluble neutrophil proteins, detection of autoantibodies by Western blot and partial amino acid sequencing were used. Two new autoantigen/autoantibody systems in patients with PSC were detected: catalase and alpha-enolase. The presence of catalase autoantibodies in 9/15 (60%) and alpha-enolase autoantibodies in 4/15 (27%) was confirmed by ELISA and Western blot. Furthermore, we showed immunoreactions of PSC sera with human biliary epithelial cells, showed the reduction of fluorescence in anti-catalase absorption experiments and observed partial co-localization of anti-catalase antibodies and PSC sera in double-staining experiments on biliary epithelial cells. The anti-catalase antibody-positive PSC patients had a more severe course of disease with a significantly higher alkaline phosphatase compared with the anti-catalase-negative PSC patients (P < 0.06). All ulcerative colitis control sera were anti-catalase antibody-negative. The identified antigens catalase and alpha-enolase can partly explain the ANCA fluorescence on ethanol-fixed and formaldehyde-fixed granulocytes in patients with PSC. Catalase is an important anti-oxidant enzyme and prevents cell damage from highly reactive oxygen-derived free radicals. Catalase autoantibodies might play a pathogenic role in patients with PSC. Our findings support the hypothesis that oxidative stress is one of the pathogenic mechanisms in patients with PSC.

Autoantibodies directed against cytoplasmic antigens of neutrophils (ANCA), especially proteinase 3 (PR-3), have proved to be a useful clinical tool confirming the diagnosis or monitoring disease activity of Wegener's granulomatosis (WG). Although several concepts concerning the pathophysiologic potentials of ANCA have been discussed, only sparse data about ANCA-endothelium interactions have been available. In this study, we have investigated the expression of PR-3 in cytokine- treated human endothelial cells using purified anti-PR-3 antibodies of patients with WG, murine and human monoclonal anti-PR-3 antibodies as probes. We were able to show that tumor necrosis factor-alpha, interleukin-1 alpha/beta, and interferon-gamma led to an increased PR-3 expression in the cytoplasm of endothelial cells by performing polymerase chain reaction analysis, Western blot, cyto-enzyme-linked immunosorbent assays, and confocal laser scanning microscopy. Moreover, PR-3 was also translocated into the cell membrane, becoming accessible to ANCA. Our data suggest a possible direct pathogenic effect of anti- PR-3 antibodies in WG and other vasculitides. Anti-PR-3 antibodies represent an important missing link in ANCA-endothelial interactions.

VCAM‐1 was first identified as an adhesion molecule induced on human endothelial cells (HEC) by inflammatory cytokines such as IL‐1, tumour necrosis factor (TNF), and lipopolysaccharide (LPS). The molecule binds to a variety of leucocytes, including B cells, T cells, basophils, eosinophils and monocytes. Vascular expression of VCAM‐1 has been associated with a number of disease states, including rheumatoid arthritis and vasculitis. The detection of antineutrophil cytoplasmic antibodies (ANCA), especially to proteinase 3 (PR3), has become important in the diagnosis of Wegener’s granulomatosis (WG) and related vasculitides. Recently we were able to demonstrate a direct effect of anti‐PR3 antibodies on neutrophil–endothelial interactions (Blood 1993; 82:1221). Binding of anti‐PR3 antibodies to their antigen translocated into the membrane of HEC leads to an enhanced adhesion of neutrophils via induction of E‐selectin (Clin Exp Immunol 1993; 94:440). The aim of this study was to investigate the effect of anti‐PR3 antibodies on the expression of VCAM‐1. HEC was isolated from umbilical vein and cultured on microtitre plates. After preincubatiion with purified anti‐PR3 antibody, purified control antibodies (SS‐A, SS‐B, RNP) (IgG and F(ab′)2 fragments) or different cytokines (controls), VCAM‐1 was detected on the surface of unfixed HEC by cyto‐ELISA and polymerase chain reaction analysis. Incubation of HEC with anti‐PR3 antibodies led to a marked increase of endothelial VCAM‐1 expression with a peak after 8 h. Incubation with TNF‐α also led to maximal VCAM‐1 expression after 4–6 h (control). Increased adhesion of T lymphocytes to HEC after binding of anti‐PR3 antibodies to their antigen could be confirmed by performing adherence assays. This effect could be inhibited by antibodies to VLA‐4. In conclusion, we have been able to show that cytokine‐like effects of anti‐PR3 antibodies on HEC are not limited to induction of neutrophil adhesion. Anti‐PR3 antibodies may thus contribute to the regulation of T lymphocyte migration from the blood by HEC in ANCA‐related vasculitides.

SUMMARY The detection of anti‐neutrophil cytoplasmic antibodies (ANCA), especially those with specificity for proteinase 3, is important in the diagnosis and in monitoring disease activity of Wegener's granulomatosis and related vasculitides. An ubiquitous feature of all ANCA‐associated acute vascular injury is lytic necrosis. Adhesion of neutrophils to endothelium is a fundamental early step of the inflammatory response. Recently we were able to show that ANCA recognize their target antigen (proteinase 3) translocated into the membrane of human endothelial cells. The aim of this study was to investigate the effect of ANCA on the adhesion of neutrophils to human endothelial cells. Incubation of endothelial cells with affinity‐purified antibodies to proteinase 3 (IgG‐ and F(ab')2‐fractions) led to a marked increase of neutrophil adhesion, with a peak after 4 h and a rapid decrease after 8 h. This effect could be inhibited by preincubation of the endothelial cells with an antibody to endothelial leucocyte adhesion molecule‐1 (ELAM‐1). Incubation with antibodies to proteinase 3 also led to an incrcase of endothelial ELAM‐1 expression as measured in a cyto‐ELISA and by flow cytometry. Our data demonstrate a direct effect of ANCA on neutrophil endothelial interactions. The enhanced adhesion of neutrophils occurs time‐dependently via induction of ELAM‐1 expression on the surface of endothelial cells. Our data give a hint of an ANCA‐mediated mechanism of endothelial injury via induction of neutrophil adhesion to vascular endothelium in Wegener's granulomatosis and other ANCA‐related vasculitides.