IntroductionMyeloperoxidase (MPO) is one of the most abundant proteins in neutrophils, accounting for 5% of the dry weight of the cell. 1 Stored in the azurophilic granules and released when neutrophils are stimulated, MPO catalyzes the oxidation of chloride and other halide ions in the presence of hydrogen peroxide 2,3 to generate hypochlorous acid and other highly reactive products that mediate efficient antimicrobial action. 4,5 Several inherited mutations and deletions in the gene encoding MPO result in decreased enzyme production and activity. 6,7 Using automated hematological devices, clinicians can distinguish between partial and complete MPO deficiencies. 8 MPO deficiency is reported to have an incidence of 1 in 2000-4000 in the United States and Europe and 1 in 55 000 in Japan. 9-13 Candida infections are common in MPO-deficient patients, especially in those that also develop diabetes. 9,14-18 Occasionally, serious infectious or inflammatory complications have been observed in completely MPOdeficient patients as well. 8 Consistently, MPO knockout mice are susceptible to particular bacterial and fungal infections. 19 Neutrophil extracellular traps (NETs) are part of the neutrophil response to microbes. Activated neutrophils die and release these structures composed of decondensed chromatin and antimicrobial proteins 20,21 that trap and inhibit a broad range of microbes. 22 Little is known about the molecular mechanism that regulates NET formation, making the antimicrobial role of NETs in vivo difficult to assess.Interestingly, neutrophils from chronic granulomatous disease (CGD) patients fail to make NETs. 20 CGD is caused by mutations that disrupt the ability of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase to generate superoxide, which dismutates to hydrogen peroxide, the substrate of MPO. CGD patients are prone to recurrent and severe infections, as well as to persistent inflammation that can occur independently of infection. [23][24][25] NET formation by CGD neutrophils is restored by the addition of exogenous hydrogen peroxide, indicating that reactive oxygen species are required for NET formation. 20 Here we show that MPO is necessary for making NETs and suggest that defective NET formation may undermine host defense in patients lacking MPO. Methods Donor consentAll donors gave consent to blood drawing in accordance with the Declaration of Helsinki and to functional and genetic analysis. Samples were collected with approval from the ethical committees at each institution. Neutrophil isolationNeutrophils were isolated by centrifuging heparinized venous blood over Histopaque 1119 (Sigma-Aldrich) and subsequently over a discontinuous Percoll (Amersham Biosciences) gradient as described previously. 20 Cells were stored in Hank buffered salt solution (-) or Dulbecco phosphatebuffered saline (-), without calcium or magnesium, before experiments. NET formation and visualizationNeutrophils (5 ϫ 10 4 ) were seeded per well in 24-well tissue culture plates, in Hanks buffered salt solution (...

Background-Perinuclear antineutrophil cytoplasmic autoantibodies (pANCA) are a well recognised marker for ulcerative colitis. Antibodies to oligomannosidic epitopes of the yeast Saccharomyces cerevisiae (ASCA) are a new marker associated with Crohn's disease. Aims-To assess the value of detecting pANCA and/or ASCA for the diagnosis of ulcerative colitis and Crohn's disease. Methods-Serum samples were obtained from 100 patients with Crohn's disease, 101 patients with ulcerative colitis, 27 patients with other miscellaneous diarrhoeal illnesses, and 163 healthy controls. Determination of pANCA and ASCA was performed using the standardised indirect immunofluorescence technique and an ELISA, respectively. Results-The combination of a positive pANCA test and a negative ASCA test yielded a sensitivity, specificity, and positive predictive value of 57%, 97%, and 92.5% respectively for ulcerative colitis. The combination of a positive ASCA test and a negative pANCA test yielded a sensitivity, specificity, and positive predictive value of 49%, 97%, and 96% respectively for Crohn's disease. Among patients with miscellaneous non-inflammatory bowel disorders, three were ASCA positive and two were pANCA positive. One control was ASCA positive. The presence of ASCA in patients with Crohn's disease was associated with small bowel involvement. Conclusion-ASCA and pANCA are strongly associated with Crohn's disease and ulcerative colitis, respectively. Combination of both tests could help the diagnosis of inflammatory bowel disease. (Gut 1998;42:788-791)

Antineutrophil cytoplasmic autoantibodies (ANCA) have been described in sera of patients with several forms of systemic vasculitis, including Wegener's granulomatosis and microscopic polyarteritis. The two main targets of ANCA in vasculitis are proteinase 3 (PR3) and myeloperoxidase (MPO). ANCA are capable of activating neutrophils primed by tumor necrosis factor-alpha (TNF-alpha) in vitro, which may be relevant for the induction of the vascular inflammation observed in vivo. Recently, it has been suggested that engagement of Fc gamma receptor IIa (Fc gamma RIIa) on the neutrophils is involved in the activation by ANCA. In the present study, we show that activation of the neutrophil respiratory burst by anti-PR3 and anti-MPO is strongly enhanced after TNF priming and lost on removal of the Fc parts of the antibodies. Similar results were obtained when the neutrophils were activated with antibodies against known membrane antigens without major changes in the expression of the target antigens. The TNF-induced enhancement of the neutrophil activation was not observed when adherence of the cells was prevented by continuous stirring of the suspension or by the addition of CD18 antibodies before TNF exposure. Hence, our results indicate that engagement of both Fc gamma RIIa and beta 2 integrins is instrumental in neutrophil activation induced by ANCA.

sCD146 is a novel marker of the endothelial intercellular junction that reflects endothelial remodeling more effectively than soluble CD31. Further studies are warranted to determine whether sCD146 will provide a serological assay reflecting alterations in vascular permeability and vessel proliferation in the inflamed IBD intestine.

No abstract

Anti-neutrophil cytoplasm autoantibodies (ANCA) directed against proteinase-3 and myeloperoxidase (MPO) activate tumor necrosis factor-alpha-primed neutrophils in vitro. We used neutrophils from one completely and one partially MPO-deficient donor to assess the requirement of MPO expression for neutrophil activation by anti-MPO antibodies. The MPO deficiencies were defined enzymatically, by immunocytochemistry and by immunoblotting. The mutations in the MPO genes of these donors were identified as a combination of a novel splice-site mutation at the 3' end of intron 11 (A-2-->C), a deletion of 14 nucleotides in exon 9 (A1555-C1568), and a novel C1907 --> T (636Thr-->Met) substitution in exon 11 in the completely MPO-deficient donor and as the same splice-site mutation and a novel C995 --> T (332Ala-->Val) substitution in exon 7 in the partially MPO-deficient donor. Monoclonal antibody 4.15 against MPO and MPO-ANCA-immunoglobulin G induced no superoxide anion production in these MPO-deficient neutrophils despite a normal production induced by other stimuli. Thus, the presence of MPO is a conditio sine qua non for neutrophil activation by anti-MPO antibodies. Moreover, we demonstrated that by means of these MPO-deficient cells, hydrogen peroxide may diffuse from neutrophils to surrounding cells, which may contribute to the damage induced by oxygen radicals in the pathology of systemic vasculitides.

No abstract

No abstract