PubMed · 11555941
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T Murakami. 2001. [Hypersensitivity vasculitis].. https://pubmed.ncbi.nlm.nih.gov/11555941/
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Antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis is the most common primary systemic small-vessel vasculitis to occur in adults. Although the etiology is not always known, the incidence of vasculitis is increasing, and the diagnosis and management of patients may be challenging because of its relative infrequency, changing nomenclature, and variability of clinical expression. Advances in clinical management have been achieved during the past few years, and many ongoing studies are pending. Vasculitis may affect the large, medium, or small blood vessels. Small-vessel vasculitis may be further classified as ANCA-associated or non-ANCA-associated vasculitis. ANCA-associated small-vessel vasculitis includes microscopic polyangiitis, Wegener's granulomatosis, Churg-Strauss syndrome, and drug-induced vasculitis. Better definition criteria and advancement in the technologies make these diagnoses increasingly common. Features that may aid in defining the specific type of vasculitic disorder include the type of organ involvement, presence and type of ANCA (myeloperoxidase-ANCA or proteinase 3-ANCA), presence of serum cryoglobulins, and the presence of evidence for granulomatous inflammation. Family physicians should be familiar with this group of vasculitic disorders to reach a prompt diagnosis and initiate treatment to prevent end-organ damage. Treatment usually includes corticosteroid and immunosuppressive therapy.
Proteinase-3 (PR-3) is a neutral serine proteinase present in azurophil granules of human polymorphonuclear leukocytes and serves as the major target antigen of antineutrophil cytoplasmic antibodies with a cytoplasmic staining pattern (c-ANCA) in Wegener's granulomatosis (WG). The WG disease appears as severe vasculitis in different organs (e.g. kidney, nose and lung). Little is known about the expression and distribution of PR-3 in the lung. We found that PR-3 is expressed in normal lung tissue and is upregulated in lung tissue of patients with WG. Interestingly, the parenchymal cells (pneumocytes type I and II) and macrophages, and not the neutrophils, express PR-3 most strongly and may contribute to lung damage in patients with WG via direct interaction with antineutrophil cytoplasmic antobodies (ANCA). These findings suggest that the PR-3 expression in parenchymal cells of lung tissue could be at least one missing link in the etiopathogenesis of pulmonary pathology in ANCA-associated disease.
Among the anti-neutrophil cytoplasmic Abs (ANCA), those targeting proteinase 3 (PR3) have a high sensitivity and specificity for Wegener's granulomatosis (WG). A pathogenetic role for these autoantibodies has been proposed due to their capacity of activating neutrophils in vitro. Recently, PR3 was also detected in human renal tubular epithelial cells (TEC). In the present study, the effect of murine monoclonal anti-PR3 Abs (anti-PR3) and purified c-ANCA targeting PR3 from WG serum on isolated human renal tubular cell signaling and inflammatory mediator release was characterized. Priming of TEC with TNF-alpha resulted in surface expression of PR3, as quantified in immunofluorescence studies and by flow cytometry. Moreover, PR3 was immunoprecipitated on surface-labeled TEC. Primed TEC responded to anti-PR3 with a dose- and time-dependent activation of phosphoinositide hydrolysis, resulting in a remarkable accumulation of inositolphosphates. Control IgG was entirely ineffective, whereas PR3-ANCA reproduced the phosphoinositide response. The signaling response was accompanied by a pronounced release of superoxidanion into the cell supernatant. Moreover, large amounts of PGE(2) and, to a lesser extent, of thromboxane B(2), the stable metabolite of TxA(2), were secreted from anti-PR3-stimulated TEC. In parallel, a rise in intracellular cAMP levels was observed, which was blocked by the cyclooxygenase inhibitor indomethacin. We conclude that anti-PR3 Abs directly target renal TECs, thereby provoking pronounced activation of the phosphoinositide-related signal transduction pathway. Associated metabolic events such as the release of reactive oxygen species and lipid mediators may directly contribute to the development of renal lesions and loss of kidney function in WG.