Recognition of bactericidal/permeability-increasing protein by perinuclear anti-neutrophil cytoplasmic antibody-positive sera from ulcerative colitis patients: prevalence and clinical significance.

BACKGROUND: The aim of this study was to evaluate a) the role of bactericidal/permeability-increasing protein (BPI) as a possible antigen determining perinuclear anti-neutrophil cytoplasmic antibody (p-ANCA) reactivity in ulcerative colitis and b) the prevalence and clinical correlates of anti-BPI antibodies in patients with ulcerative colitis on the basis of their p-ANCA status. METHODS: p-ANCA and anti-BPI antibodies were evaluated by means of indirect immunofluorescence and enzyme-linked immunosorbent assay methods in a group of 112 ulcerative colitis patients (including 42 patients subjected to proctocolectomy) well defined as far as their clinical features and p-ANCA status. RESULTS: Anti-BPI antibodies were detected in 24% of non-operated patients and were significantly more frequent in p-ANCA-positive patients (32% versus 5% in p-ANCA-negative patients; P < 0.015). The prevalence of anti-BPI antibodies was similar in non-operated and operated patients and was high in men, in patients with an extensive and aggressive disease, and in patients developing pouchitis after surgery. CONCLUSIONS: These data indicate that BPI is a neutrophil antigen frequently recognized by p-ANCA-positive ulcerative colitis sera. The presence of anti-BPI antibodies appears to identify further immunologic and clinical heterogeneity in ulcerative colitis.

alpha 1-Antitrypsin (AAT) deficiency and ANCA-positive systemic vasculitis: genetic and clinical implications.

A high incidence of alpha 1-antitrypsin (AAT) deficiency has been reported in patients with C-ANCA systemic vasculitis in association with antibodies against proteinase-3 (PR3). To clarify the role of AAT deficiency in the acute vasculitic process as well as in progression of the disease, we studied 84 patients with either C-ANCA or P-ANCA vasculitis with special reference to: (a) the AAT gene, (b) the phenotypic (Pi) variants and (c) the serum levels during both acute illness and remission. The PiZ gene was found in six patients (8% vs. 1.5% controls) irrespective of the type of autoantibodies (C-ANCA vs. P-ANCA). All PiZ patients displayed the ability to raise their AAT serum levels up to the normal range during acute illness. In contrast, 24 patients with the PiM phenotype presented low AAT serum levels during acute illness. In all these patients, the AAT levels returned to normal values during the remission. Low AAT levels were associated with low levels of C-reactive protein (PCR) (P < 0.001), with a less severe renal involvement or a minor risk of death, and, in one tested patient, with a novel point mutation (TCGA-->TCAA) at the enhancer-promoter region of the AAT gene. Low AAT serum levels did not correlate with either type/titre of autoantibody or distribution/severity of the vasculitis process. In the case-control study, high AAT levels emerged as a major determinant of progression towards end-stage renal failure [odds ratio 3 (95% CI 1.1-8.4)]. These results indicate: (a) a high incidence of the PiZ gene of AAT in systemic vasculitis irrespective of the type of autoantibodies; (b) a novel form of AAT deficiency associated with the normal PiM phenotype becoming manifest only during acute illness; (c) dysregulation of the acute-phase response affecting selectively AAT or both AAT and PCR; (d) correlation between low plasma levels of AAT and less severe renal involvement or risk of death.

Induction of experimental SLE in naive mice by immunization with human polyclonal anti-DNA antibody carrying the 16/6 idiotype.

Recently, the induction of SLE in naive mice employing monoclonal anti-DNA antibodies (anti-DNA Ab) carrying the pathogenic idiotype 16/6 (16/6 Id) has been reported. In the current study we report on the induction of experimental SLE by polyclonal IgG anti-DNA Ab derived from a patient with active SLE and carrying the 16/6 Id. Two different experiments were conducted in which BALB/c mice were immunized in the footpads with 1 microgram/ml or 5 micrograms/ml of anti-DNA Ab. The first experiment showed the appearance in the immunized mice of high titre anti-DNA Ab together with antinuclear antibodies, alopecia and proteinuria. In the second experiment we compared, as immunizing agents, 16/6 positive anti-DNA Ab and 16/6 negative anti-tetanus toxoid antibodies (anti-TT Ab) obtained from the serum of the same patients. Our results show that only mice immunized with 16/6 positive antibodies produced anti-DNA Ab, while mice immunized with anti-TT Ab did not show any DNA-binding activity but, surprisingly, developed high titre anti-cardiolipin antibodies.

Antibodies to endothelial cells in primary vasculitides mediate in vitro endothelial cytotoxicity in the presence of normal peripheral blood mononuclear cells.

Twenty-eight out of 62 patients with Wegener's granulomatosis and micropolyarteritis display circulating antiendothelial cell antibodies (AECA) detectable by a cell surface radioimmunoassay. These antibodies do not induce an in vitro endothelial damage either alone or in the presence of fresh complement; however, 50% of IgG-AECA positive sera can be cytotoxic in the presence of human normal peripheral blood mononuclear cells (PBM) at high effector/target ratios. The specificity of the PBM-mediated cytotoxicity is supported by the absence of the phenomenon in AECA negative sera, by the disappearance of the lytic effect after absorption of AECA, and by the finding that cellular-mediated cytotoxicity can be reproduced by purified IgG-AECA positive fractions. On the contrary, polymorphonuclear leukocytes or adherent mononuclear cells are not involved in such a cytotoxic activity. AECA seem to be directed against determinants consitutively expressed on the endothelial surface since the activation of endothelial cells by interleukin-1 beta or interferon-gamma affects neither the antibody binding nor their ability to mediate 51Cr release in the presence of PBM. These findings favor the hypothesis for a possible direct pathogenetic role of circulating AECA in the in vivo vascular damage.

Anti-endothelial cell antibodies in patients with Wegener's granulomatosis and micropolyarteritis.

Anti-endothelial cell antibodies (AECA) have been detected by cell surface radioimmunoassay in nine out of 15 patients with micropolyarteritis (MPA) and in two out of five patients with Wegener's granulomatosis. AECA mostly belonged to the IgG isotype and were present in the active phase of the diseases. These antibodies were not detectable in 10 sera from patients with essential mixed cryoglobulinaemia, suggesting that they were not a mere epiphenomenon consequent to the inflammatory vascular injury. The binding activity was not related to ABH antigens or to HLA class I antigens displayed by resting human endothelial cells in culture and was not influenced by removing immune complexes. Absorption of the anti-neutrophil cytoplasmic antibodies (ANCA), present in MPA and Wegener's granulomatosis sera, did not affect the endothelial binding. AECA-positive sera did not display lytic activity against endothelial cells, neither alone nor after addition of fresh complement or normal human peripheral blood mononuclear cells. Although AECA are not cytolytic for endothelial cell monolayers in vitro, the reactivity against intact endothelial cells suggests their possible involvement in in vivo pathological processes affecting vascular structures in small vessel primary vasculitides.