[Pathogenesis of primary systemic vasculitides (I): ANCA-positive vasculitides]. / Pathogénie des vascularites systémiques primitives (I): vascularites ANCA-positives.

The pathogenesis of different types of systemic vasculitis positive for antineutrophil cytoplasmic antibodies (ANCA) remains incompletely understood. ANCA constitute a heterogeneous group of antibodies that are associated with different types of small-vessel vasculitis, including Wegener's granulomatosis (WG), microscopic polyangiitis (MPA) and Churg-Strauss syndrome (CSS). Anti-proteinase 3 ANCA are present in more than 90% of patients with systemic WG, and anti-myeloperoxidase (MPO) ANCA in 50-75% of those with MPA and 40-60 % of those with CSS. The pathogenic role of ANCA has been well documented in vivo: passive transfer of anti-MPO ANCA in an MPO knockout mouse model immunized with MPO is sufficient to induce the disease. In vitro, mouse and human anti-proteinase 3 ANCA can activate neutrophils primed with TNF-a and contribute to vasculitic lesions. T-cells are also involved: type 1 helper cytokines have been detected in tissue lesions of limited forms of WG, while type 2 helper cytokines have been identified in its systemic forms. Eosinophils may play a key role in the development of vasculitic lesions in CSS, although this remains to be proved.

[Pathogenesis of primary systemic vasculitides (II): ANCA-negative vasculitides]. / Pathogénie des vascularites systémiques primitives (II): vascularites ANCA-négatives.

The pathogenesis of different types of systemic vasculitis negative for antineutrophil cytoplasm antibodies (ANCA) and involving small or medium-sized vessels is not very well documented. During polyarteritis nodosa (PAN), which is related to hepatitis B virus (HBV) infection, as well as during cryoglobulinemic vasculitides, associated with hepatitis C virus (HCV), and probably during Henoch Schönlein purpura, histological lesions may result from the deposition of immune complexes formed from viral antigens and from antibodies responsible for the activation of the classic complement pathway and for recruitment of polymorphonuclear neutrophils. Two other mechanisms are discussed for other types of ANCA-negative systemic vasculitis: immune complex deposition and sheer stress at arterial bifurcation points. A bacterial superantigen is suspected in Kawasaki disease but remains unproved.

Anti-endothelial cell antibodies in idiopathic and systemic sclerosis associated pulmonary arterial hypertension.

BACKGROUND: It has previously been shown that IgG antibodies from patients with limited cutaneous systemic sclerosis (SSc) bind to specific microvascular endothelial cell antigens. Since patients with limited cutaneous SSc are prone to develop pulmonary arterial hypertension (PAH), and since endothelial cell activation is involved in the pathogenesis of idiopathic PAH (IPAH), a study was undertaken to examine the presence of anti-endothelial cell antibodies in patients with idiopathic or SSc associated PAH. METHODS: PAH was confirmed by right heart catheterisation (mean pulmonary artery pressure at rest >25 mm Hg). Serum IgG and IgM reactivities were analysed by immunoblotting on human macrovascular and microvascular lung and dermal endothelial cells from patients with IPAH (n = 35), patients with PAH associated with SSc (n = 10), patients with diffuse (n = 10) or limited cutaneous (n = 10) SSc without PAH, and 65 age and sex matched healthy individuals. RESULTS: IgG antibodies from patients with IPAH bound to a 36 kDa band in macrovascular endothelial cell extracts with a higher intensity than IgG from other patient groups and controls. IgG antibodies from patients with IPAH bound more strongly to a 58 kDa band in microvascular dermal endothelial cells and to a 53 kDa band in microvascular lung endothelial cells than IgG antibodies from other patients and controls. IgG antibodies from patients with limited cutaneous SSc with or without PAH, but not from other groups or from healthy controls, bound to two major bands (75 kDa and 85 kDa) in microvascular endothelial cells. CONCLUSION: IgG antibodies from patients with idiopathic or SSc associated PAH express distinct reactivity profiles with macrovascular and microvascular endothelial cell antigens.