Abstract
ObjectivesPentraxin 3 (PTX3), in common with myeloperoxidase and proteinase 3, is stored in humanneutrophil granules and is expressed on apoptotic neutrophil surface. We therefore investigatedthe presence of anti-PTX3 autoantibodies (aAbs) in the sera of antineutrophil cytoplasmicantibodies (ANCA)-associated vasculitis (AAV) patients.MethodsPresence of anti-PTX3 autoantibodies was analysed by a specific enzyme-linked immunosorbentassay in sera from 150 patients with microscopic polyangiitis (MPA), granulomatosiswith polyangiitis (GPA), and eosinophilic granulomatosis with polyangiitis (EGPA), andin sera of 227 healthy subjects (HS), 40 systemic sclerosis (SSc) patients, and 25 giant cellarteritis patients (GCA). Using indirect immunofluorescence on fixed human neutrophils, wealso analyzed the staining pattern associated with the presence of anti-PTX3 aAbs.ResultsAnti-PTX3 aAbs were detected in 56 of 150 (37.3%) of the AAV patients (versus 12 of 227(5.3%) of HS, p<0.001) and, interestingly, in 7 of 14 MPO and PR3 ANCA negative AAVpatients. Moreover, by indirect immunofluorescence on fixed neutrophils, anti-PTX3 aAbsgave rise to a specific cytoplasmic fluorescence pattern distinct from the classical cytoplasmic(c-ANCA), perinuclear (p-ANCA), and atypical (a-ANCA) pattern. Anti-PTX3 aAbslevels were higher in patients with active AAV as compared to patients with inactivedisease.ConclusionOur work suggests that PTX3 is as a novel ANCA antigen. Anti-PTX3 aAbs appear thus asa promising novel biomarker in the diagnosis of AAV, including in patients without detectableMPO and PR3 ANCA.