Mechanisms of endothelial cell injury in vasculitis

The aetiology of the primary systemic vasculitides remains obscure. Recent years have seen significant advances in our understanding of inflammation and in particular the role of and interaction between the vascular endothelium, mediators and immune effector cells. This has helped to further elucidate those specific processes relevant to vasculitis which result in endothelial cell damage. In Wegener's granulomatosis and microscopic polyarteritis the evidence favours an autoimmune inflammatory response characterised by specific mediators in which the endothelium is both target and active participant. Current treatment of these disorders with combinations of corticosteroids and cytotoxics is highly effective in inducing remission. However, long-term use of this therapy is potentially toxic and there remains also a significant risk of relapse. It is hoped that increased understanding of the pathogenesis of systemic vasculitis will enable more specific, less toxic and more effective therapies to be defined. Jayne et al. have suggested a beneficial effect of intravenous pooled normal human immunoglobulin (IVIG) in patients with ANCA-positive vasculitis. In vitro studies have shown that IVIG contains antiidiotypic antibodies to ANCA and AECA, capable of inhibiting the binding of these autoantibodies to their autoantigens. In vivo, IVIG may also provide the immunoregulatory elements needed for the idiotype network and control of the autoimmune repertoire. Mathieson et al. successfully used monoclonal antibodies to T cells (Campath-H directed against CDw52) in a patient with ANCA-negative dermal lymphocytic vasculitis. Monoclonal antibodies to CAMs have been used in human renal transplant rejection and reduced the inflammation and proteinuria in animal models of anti-glomerular basement membrane disease. In vasculitis, the therapeutic use of specific anti-CAM antibodies may result from further definition of the role of CAMs. Increased understanding of the pathogenesis of systemic vasculitis is likely to provide the basis for the use of more specific immunotherapies in the future.