Diverse target antigens recognized by circulating antibodies in anti-neutrophil cytoplasm antibody-associated renal vasculitides.

Antibodies that are directed against cytoplasmic constituents of neutrophils and monocytes (anti-neutrophil cytoplasm antibodies, ANCA) have been described in Wegener's granulomatosis, microscopic polyarteritis (MPA) and some cases of segmental necrotizing glomerulonephritis (SNGN). Other antibodies occasionally described in Wegener's granulomatosis and MPA include anti-nuclear antibodies (ANA) and anti-glomerular basement membrane (GBM) antibodies. We have studied the diversity of the corresponding antigens in ANCA-associated renal diseases. Sera from 46 patients with active histologically proven Wegener's granulomatosis, MPA and SNGN were tested for ANCA by indirect immunofluorescent examination of normal peripheral blood neutrophils. Thirty-four sera (74%) were positive; 16 were associated with diffuse cytoplasmic staining (cANCA) and 18 with perinuclear staining (pANCA). In addition, five demonstrated antineutrophil-specific nuclear staining (ANNA). On Western blotting of the neutrophil extract, five sera recognized a 29-kD molecule recently identified as neutrophil proteinase 3. Two sera with typical cANCA bound to molecules of 36, 38 and 116 kD and another to a molecule of 22 kD. The final serum associated with pANCA bound to a molecule of about 12 kD. Thirteen sera out of 46 (28%) tested in an ELISA contained anti-myeloperoxidase antibodies; 10 of these were associated with pANCA and two others with ANNA. Three sera of 17 (18%) tested contained anti-elastase antibodies; these also contained anti-myeloperoxidase antibodies and were associated with pANCA. However, eight sera with pANCA were negative for anti-myeloperoxidase antibodies and three of these were also negative for anti-elastase antibodies, suggesting further unidentified target antigen or antigens associated with the pANCA. Fifteen of the 34 sera positive for ANCA also demonstrated anti-nuclear staining on Hep-2 cells (53%) in a speckled, homogeneous, or nucleolar pattern. ANA were significantly associated with the presence of pANCA (P less than 0.01), and levels of ANA and ANCA fell in parallel after treatment. One serum with a pANCA was also positive for anti-GBM antibodies. Inhibition studies using ELISAs for anti-GBM antibodies indicated that there was no cross-reactivity between target molecules recognized by these antibodies. The diversity of target molecules recognized by ANCA suggests that cross-reactivity with bacterial structures is less likely as the primary aetiological event in the development of these antibodies than tissue destruction; and that cross-reactivity with vascular endothelium is also unlikely as the pathogenetic basis of vessel disease.