THE AUTOIMMUNE BASIS OF ANCA POSITIVE SYSTEMIC VASCULITIS

Autoimmunity is usually taken to mean the existence of autoreactive components of the immune system that result in tissue damage. This last qualification is important, as it is possible to demonstrate autoreactivity in both humoral (1) and cellular compartments (2) of the immune system in normal individuals. The systemic vasculitides are a group of disorders characterised by necrotizing inflammation of blood vessels. They have long been thought to have an autoimmune basis, but it is only relatively recently that direct evidence for autoreactivity has been obtained ; the extent to which this autoreactivity contributes to pathogenesis is still controversial. We will attempt in this article to briefly review the data concerning autoreactivity in systemic vasculitis, and discuss the evidence that this contributes to pathogenesis. Although non-specific elements of the immune system (complement, polymorphs, macrophages) are undoubtedly involved in the mediation of autoimmune disease, such elements need to be engaged by the specific recognition components, namely autoantibodies on the humoral side and autoreactive T cells on the cellular side. We will therefore focus our discussion on these specific elements.