Antineutrophil cytoplasmic autoantibodies, autoantigens, and systemic vasculitis

Granulomatous lung disease: clinical aspects

INTRODUCTION

Granulomatous lung diseases (GLD) are heterogeneous group of diseases that can be broadly categorized as infectious or noninfectious. This distinction is extremely important, as the misdiagnosis of a GLD can have serious consequences. In this manuscript, we describe the clinical manifestations, histopathology, and diagnostic approach to GLD. We propose an algorithm to distinguish infectious from noninfectious GLD.

AREAS COVERED

We have searched PubMed and Medline database from 1950 to December 2019, using multiple keywords as described below. Major GLDs covered include those caused by mycobacteria and fungi, sarcoidosis, hypersensitivity pneumonitis, and vasculidities.

EXPERT OPINION

The cause of infectious GLD is usually identified through microbiological culture and molecular techniques. Most noninfectious GLD are diagnosed by clinical and laboratory criteria, often with exclusion of infectious pathogens. Further understanding of the immunopathogenesis of the granulomatous response may allow improved diagnosis and treatment of GLD.

Duodenal expression of antimicrobial peptides in dogs with idiopathic inflammatory bowel disease and intestinal lymphoma

Although antimicrobial peptides (AMPs) play an integral role in the regulation of intestinal microbiota and homeostasis, their expression in canine gastrointestinal diseases, including idiopathic inflammatory bowel disease (IBD) and intestinal lymphoma, remains unknown. The objective of this study was to investigate the intestinal expression of AMPs in dogs with IBD or intestinal lymphoma. IBD was diagnosed in 44 dogs, small cell intestinal lymphoma in 25 dogs, and large cell intestinal lymphoma in 19 dogs. Twenty healthy beagles were used as normal controls. Duodenal mRNA expression of six representative AMPs - lactoferrin, lysozyme, cathelicidin, secretory leukocyte peptidase inhibitor (SLPI), bactericidal/permeability increasing protein (BPI), and canine beta defensin (CBD103) - was quantified by real-time reverse transcription polymerase chain reaction. The relative expression of BPI, lactoferrin, and SLPI was significantly higher in dogs with IBD and intestinal lymphomas than in healthy controls. Interestingly, the expression patterns of AMPs differed between dogs with IBD and those with intestinal lymphomas, especially small cell lymphoma. Increased expression of BPI differentiated IBD from dogs with small cell intestinal lymphoma, with a sensitivity of 93.2%, a specificity of 100%, and an area under the curve of 0.955. These results suggest that the expression patterns of AMP aid in the diagnosis of canine IBD and intestinal lymphoma, although it remains uncertain whether the altered AMP expression is the cause or effect of mucosal inflammation.

Late onset lupus nephritis: analysis of clinical manifestations and renal pathological features in Chinese patients

The objectives of the study are to analyze the clinical and pathological features of 35 Chinese patients with late onset lupus nephritis (LN) in a single center. All the LN patients followed-up in our lupus clinic center from 1986 to 2008 were enrolled in this retrospective study. Thirty-five patients with a disease onset beyond the age of 50 years were identified. One hundred systemic lupus erythematosus (SLE) patients who had their disease onset before the age of 50 years were randomly recruited as controls. All of them received renal biopsy. The histological classifications were categorized according to 2003 International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification. All of patients were Han Chinese. The mean age of onset of SLE for late onset and the control groups were 55.7 ± 6.5 years (range: 50-76) and 28.9 ± 7.6 years (range:18-48).The female to male ratio was smaller in the late onset SLE group, 2.9-1, compared with 7.3-1 in the control. The patients with hypertension in late onset LN were much more than that in control group. The renal histological classes showed no significant difference between the two groups. Classes IV, V, IV + V were common in late onset LN patients. There were no significant differences in extra renal manifestations except for a lower prevalence of malar rash, a higher leukopenia and skin vasculitis in the late onset patients. As to the immunological features, serum antineutrophil cytoplasmic antibodies (ANCA) and SSA positivity were more common in late onset LN patients. The patients with hypertension in late onset LN were much more than that in control group. The renal histological classes showed no significant difference between the two groups. Leukopenia and serum ANCA were more common. The results suggest a more severity of the disease in late onset LN.

Systemic granulomatous necrotizing vasculitis in a MPO-ANCA-positive patient

We present a case of myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA)-associated vasculitis that demonstrated a systemic granulomatous lesion at autopsy. The patient initially showed anorexia, general malaise and anemia. Colon fiber was examined to detect the bleeding site, which revealed ischemic mucosal damage associated with venous fibrin thrombus. Because a high titer of MPO-ANCA was found, ANCA-associated vasculitis was suspected and the patient was started on steroid pulse therapy. However, anemia, renal failure and respiratory failure worsened and the patient died of sudden cardiac failure 2 days after the start of the therapy. An autopsy revealed systemic arteritis in multiple organs including the kidneys, liver, spleen, gastrointestinal system and genital organs that indicated fibrinoid necrosis accompanied by granulomatous reaction with multinucleated giant cells; the granulomatous reaction further extended along the splenic capsule. Glomerulonephritis and diffuse pulmonary damage, which are common in MPO-ANCA-associated vasculitis, were almost absent but parapleural fibrosis was present. The direct cause of death was presumed to be hemorrhagic shock due to rupture of an aneurysm in the gastric subserosa. As far as we know, this is the first case of a systemic granulomatous reaction in MPO-ANCA-positive vasculitis, although the cause of the granulomatous lesion is unknown.

Advances in clinical laboratory tests for inflammatory bowel disease

Inflammatory bowel disease (IBD) is a generic term that refers to Crohn's disease and chronic ulcerative colitis (UC). The CD and UC are considered to be distinct forms of IBD; but there is a subgroup of CD with a UC-like presentation. The genetic factors play a significant role in IBD. IBD is associated with a strong familial pattern. Recent studies support the hypothesis that IBD patients have a dysregulated immune response to endogenous bacteria in the gastrointestinal tract. The serologic responses seen in Crohn's disease include antibodies to Saccharomyces cerevisiae, mycobacteria, bacteroides and E. coli. The pANCA antibody seen in UC and CD has been demonstrated to react with epitopes of H1 histone, Bacteroides caccae (Ton-B linked outer membrane protein), Pseudomonas fluorescens-associated bacterial protein I-2, mycobacterial histone 1 homologue called Hup B. In recent years, several serologic markers have been found to be useful for the diagnosis and differentiation of CD and UC. These markers include the following antibodies: (a) pANCA, (b) ASCA, (c) anti-pancreatic antibody, (d) OmpC antibody and (e) I-2 antibody and antibodies to anaerobic coccoid rods. The application of a panel of markers with the use of an algorithm (i.e. IBD First Step) can identify specific subtypes of IBD that have different clinical courses and progression of the diseases. The serologic markers are useful for the diagnosis and management of CD and UC patients.

Cutaneous Wegener's granulomatosis: a variant or atypical localized form?

A 74-year-old woman presented with an antineutrophil cytoplasmic antibody titre-negative, treatment-responsive Wegener's granulomatosis confined to the integument. She initially presented with a painful left postauricular nodulo-ulcerative lesion with chronically discharging sinuses. This lesion was effectively treated with a short, 3-month course of cyclophosphamide and 24 months of oral prednisone. After 5 months in remission, she developed further similar ulcers, in addition to painless nodules on her ankles and feet bilaterally. These lesions resolved with an extra 32 months of high-dose oral prednisone therapy before complete remission. At most recent review, there was no evidence of disease recurrence 21 months after ceasing all active treatment. Histology demonstrated a granulomatous inflammation. No systemic disease progression to the upper respiratory tract, lung or kidney was detected. This case highlights the importance of being aware of atypical or partial presentations of Wegener's granulomatosis. This diagnosis needs to be considered with patients presenting with a culture-negative chronic ulcer, where malignancy and trauma have been excluded. This will avoid unnecessary surgery and ensure early diagnosis and effective treatment of a disease that is disfiguring and usually fatal if inappropriately treated.

Serological markers in inflammatory bowel diseases

This chapter is an overview of the literature on serological markers of inflammatory bowel diseases (IBD), focusing on anti-neutrophil cytoplasm autoantibodies (ANCA) and anti- Saccharomyces cerevisiae mannan antibodies (ASCA). The methodology for ANCA and ASCA testing is first introduced. The value of these markers as diagnostic tools is then discussed. Other chapters are devoted to the potential role of ANCA and ASCA in disease monitoring, disease stratification and as subclinical markers in families. Finally reviewed are other antibodies recently tested in clinical trials such as pancreatic antibodies and antibodies directed against bacterial antigens. The role of these antibodies in the pathophysiology of IBD still needs to be assessed. We also need to identify the ASCA immunogen(s) eliciting the antibody response.

Increased expression of the secretory leukocyte proteinase inhibitor in Wegener's granulomatosis

The secretory leucocyte proteinase inhibitor (SLPI) is a low molecular weight, tissue-specific inhibitor of proteases, such as elastase and cathepsin G. It is the major local protease inhibitor in the upper airways. Proteinase 3, the main autoantigen in Wegener's granulomatosis (WG), can degrade SLPI proteolytically. In addition, SLPI is sensitive to oxidative inactivation by myeloperoxidase-generated free oxygen radicals. SLPI also has an antimicrobial capacity that can be of interest, as infection is considered to play a role in the pathogenesis of WG. This study focuses on SLPI expression in patients suffering from WG, something that to our knowledge has not been explored hitherto. Serum samples and nasal biopsies were obtained from 12 Swedish WG patients, while buffy coats were obtained from 33 American WG patients. SLPI levels in serum were measured by means of ELISA and the protein was detected by means of immunohistochemistry in nasal biopsies. mRNA expression was studied by means of in situ hybridization on nasal biopsies and RT-PCR on leucocytes. IL-6 or ESR were measured as markers of inflammatory activity. Cystatin C or creatinine was measured as a marker of renal filtration. White blood cell counts were registered. In serum, we found close to normal SLPI levels, without any correlation to IL-6. Two patients had greatly elevated values, both of them suffering from severe renal engagement. Strong SLPI mRNA expression was found in nasal biopsies. RT-PCR on leucocyte mRNA showed normal or greatly elevated expression of SLPI mRNA, correlating with disease activity. Leukocyte SLPI expression seems to be up-regulated in active WG. Serum levels were measured in a small number of patients and were found to be close to normal. Lack of correlation to the acute phase response indicates a specific regulation. This might be linked to an altered protease/antiprotease balance. These findings could indicate that SLPI locally participates in the anti-inflammatory and perhaps antimicrobial response in WG.

Beyond neurons: evidence that immune and glial cells contribute to pathological pain states

Chronic pain can occur after peripheral nerve injury, infection, or inflammation. Under such neuropathic pain conditions, sensory processing in the affected body region becomes grossly abnormal. Despite decades of research, currently available drugs largely fail to control such pain. This review explores the possibility that the reason for this failure lies in the fact that such drugs were designed to target neurons rather than immune or glial cells. It describes how immune cells are a natural and inextricable part of skin, peripheral nerves, dorsal root ganglia, and spinal cord. It then examines how immune and glial activation may participate in the etiology and symptomatology of diverse pathological pain states in both humans and laboratory animals. Of the variety of substances released by activated immune and glial cells, proinflammatory cytokines (tumor necrosis factor, interleukin-1, interleukin-6) appear to be of special importance in the creation of peripheral nerve and neuronal hyperexcitability. Although this review focuses on immune modulation of pain, the implications are pervasive. Indeed, all nerves and neurons regardless of modality or function are likely affected by immune and glial activation in the ways described for pain.

Human proteinase 3 can inhibits LPS-mediated TNF-alpha production through CD14 degradation: lack of influence of antineutrophil cytoplasmic antibodies

The present study was conducted to investigate if proteinase-3 (PR3) is able to influence lipopolysaccharide (LPS) responses of monocytes via degradation of CD14 and if antineutrophil cytoplasmic antibodies (ANCA) may modify this process. Recombinant (r) CD14 and CD14 expressed on monocytes were investigated for PR3 mediated degradation by SDS-PAGE and FACS analysis, respectively. TNF-alpha production in whole blood was used to determine functional consequences of CD14 degradation. PR3 degraded rCD14 in a dose- and time-dependent fashion. Major degradation products were found with apparent molecular weight of 45, 25 and 10 kDa. Treatment of PR3 with PMSF completely abolished CD14 degradation. ANCA IgG did not inhibit CD14 degradation. In whole blood, addition of PR3 resulted in diminished CD14 expression on monocytes. In contrast, CD14 was increased in a subpopulation of cells that expressed major histocompatibility (MHC) class II and PR3, but lacked expression of CD64 and CD16. LPS mediated TNF-alpha production in whole blood was significantly inhibited when preincubated with PR3. This study demonstrates that PR3 can degrade rCD14 and that PR3 differentially affects CD14 expression in subsets of monocytes. ANCA IgG does not play a significant role herein.

Vitronectin- and fibronectin-containing immune complexes in primary systemic vasculitis

In primary systemic vasculitis anti endothelial cell autoantibodies (AECA) have been described frequently. They represent a heterogeneous group of autoantibodies whose target antigens are mostly unknown. We tried to find AECA-antigens by a co-operative binding assay with a panel of monoclonal antibodies (mAb) directed to human umbilical vein endothelial cells (HUVEC) and extracellular matrix proteins. The mAb were used to bind antigens from lysate of endothelial cells, and binding of human antibodies to these antigens was measured. mAb directed to Vitronectin (VN) and Fibronectin (FN) resulted in enhanced binding of antibodies in sera from patients with Churg Strauss Syndrome (CSS) and Wegener's Granulomatosis (WG) compared to normal sera. Neither free autoantibodies against VN or FN could be detected nor did the addition of endothelial cell lysate influence the binding activity from the patients' sera. This suggests that preformed VN and FN-containing immune complexes (IC) are present in the patient sera. The amount of IC was decreased by incubation with HUVEC, demonstrating that these IC can bind to endothelial cells. However, their involvement in the pathogenesis of the disease is not clearly defined. Our data suggest that there are preformed IC present in sera of patients with CSS and WG that contain VN and FN and bind to endothelial cells.

Contribution of myeloperoxidase to coronary artery vasculitis associated with MPO-ANCA production

The role of myeloperoxidase (MPO) in the pathogenesis of vasculitis associated with MPO-specific anti-neutrophil cytoplasmic autoantibody (MPO-ANCA) was examined in a murine animal model. Coronary artery vasculitis was induced in C57BL/6 mice with and without endogenous MPO by intraperitoneal injection of Candida albicans-derived substances (CADS). The corresponding levels of MPO-ANCA in sera of mice with and without vasculitis were measured and compared in both wild-type and MPO-deficient animals. The MPO-ANCA titers in sera were significantly higher in mice with vasculitis than in vasculitis-negative mice, indicating that MPO-ANCA correlated with vasculitis formation. However, the increase of MPO-ANCA titers observed in sera of wild C57BL/6 mice were strongly suppressed in MPO-deficient C57BL/6 mice, accompanied with prevention of vasculitis formation. These results show that MPO acted as an antigen for MPO-ANCA production by CADS and was followed by the vasculitis formation. Vasculitis did develop in a few MPO-deficient mice, though the incidence of vasculitis was much lower in MPO-deficient mice than in C57BL/6 mice.

Polymorphonuclear neutrophils in Wegener's granulomatosis acquire characteristics of antigen presenting cells

BACKGROUND

Constitutive expression of major histocompatibility complex (MHC) class II antigens and of the co-stimulatory receptors CD80 and CD86 is restricted to professional antigen presenting cells. Polymorphonuclear neutrophils (PMN) of healthy donors are negative for those antigens. Our recent study, however, found that PMN of patients with active Wegener's granulomatosis acquired MHC class II antigens.

METHODS

To continue and extend the previous study results, PMN and monocytes of 60 patients with Wegener's granulomatosis, 24 patients with microscopic polyangiitis (MPA), 20 patients with acute bacterial infection, and 53 healthy donors were analyzed for the expression of MHC class II antigens as well as of CD80 and CD86. Moreover, induction on PMN of MHC class II expression was studied, as was antigen presentation as a possible functional consequence.

RESULTS

PMN of patients with acute, active Wegener's granulomatosis expressed MHC class II antigens, CD80 and CD86; on monocytes up-regulation of MHC class II was seen. In contrast, PMN of patients with inactive disease, or with relapse, patients with microscopic polyangiitis or with bacterial infections expressed neither MHC class II, nor CD80 or CD86. PMN of healthy donors acquired these antigens when cultured in the presence of T cells or T cell-derived cytokines. The PMN were then able to present to T cell antigens in a MHC-class II restricted manner.

CONCLUSION

During active disease, the PMN of patients with Wegener's granulomatosis acquire characteristics of antigen presenting cells, whereas the PMN of patients with MPA or bacterial infection do not. The finding reflects differences in the pattern of the respective inflammatory response and suggests new effector functions of PMN. Moreover, MHC class II expression on PMN could serve as a novel marker for active Wegener's granulomatosis.

Recent advances in the diagnosis of Churg-Strauss syndrome

Most pathologists assume that a diagnosis of Churg-Strauss syndrome (CSS) requires the finding of necrotizing vasculitis accompanied by granulomas with eosinophilic necrosis in the setting of asthma and eosinophilia. However, recent data indicate that this definition is too narrow and that adherence to it leads to cases of CSS being missed. CSS has an early, prevasculitic phase that is characterized by tissue infiltration by eosinophils without overt vasculitis. Tissue infiltration may take the form of a simple eosinophilia in any organ, and a fine-needle aspirate showing only eosinophils may suffice for the diagnosis in this situation. The prevasculitic phase appears to respond particularly well to steroids. Even in the vasculitic phase of CSS, many cases do not show a necrotizing vasculitis but often only an apparently nondestructive infiltration of vessel walls by eosinophils. In modern biopsy materials, granulomas frequently cannot be found. In the postvasculitic phase of CSS, healed vascular lesions resemble organized thrombi but typically show very extensive destruction of elastica and, often, an absence of eosinophils. The widespread use of steroids as therapy for asthma has led to the peculiar and confusing situation in which the steroid therapy accidentally suppresses CSS and changes in steroid treatment uncover the disease; this type of "formes frustes" CSS is now well recognized with leukotriene receptor antagonist treatment and will be seen with increasing frequency as other steroid-sparing therapies for asthma are introduced.

Histological diversity of vasculitic lesions in MPO-ANCA-positive autopsy cases

To investigate the variety of histological features of vasculitic lesions in myeloperoxidase-specific antineutrophil cytoplasmic antibody (pANCA)-related vasculitis, retrospective pathological analysis was done on 13 autopsy cases, collected from 1990 to 1998 at five hospitals. These cases were classified into three groups: (i) pulmonary-renal syndrome characterized by capillaritis of lung and glomeruli with occasional small-vessel arteritis and/or phlebitis; (ii) glomerular capillaritis without pulmonary involvement associated with significant small-vessel arteritis; and (iii) extensive distribution of small-vessel arteritis with no capillary involvement. The results suggest that pANCA-related vasculitis encompasses a wide variety of vasculitic syndromes, including pulmonary-renal syndrome, microscopic polyarteritis nodosa, and classic polyarteritis nodosa. pANCA may contribute to pathogenesis in all of these cases.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Target antigens for anti-neutrophil cytoplasmic autoantibodies (ANCA) are on the surface of primed and apoptotic but not unstimulated neutrophils

The reaction of ANCA with ANCA antigens on the surface of neutrophils may play a critical role in the pathogenesis of ANCA vasculitis. Therefore, an understanding of the circumstances that result in surface expression of these antigens is important for an understanding of pathogenic mechanisms. In this study we investigated the surface expression of ANCA antigens on quiescent, primed, and apoptotic neutrophils. ANCA antigens and other granule constituents were not detected on the surface of neutrophils in freshly heparinized blood. ANCA antigens were on the surface of neutrophils primed by in vitro incubation for 4 h and 8 h. These cells did not show evidence of apoptosis. After 24 h incubation, about 30% of the neutrophils were apoptotic, and ANCA antigens and other granule constituents were present on the surface of both apoptotic and non-apoptotic cells. Our data indicate that there are no ANCA antigens on the surface of quiescent neutrophils, but that they are on the surface of primed neutrophils before the cells become apoptotic, and remain on the surface of cells after they become apoptotic. Based on these observations, we hypothesize that ANCA can react in vivo with primed but not quiescent neutrophils. Previously published observations indicate that the interaction of ANCA with primed neutrophils results in neutrophil activation, which may be involved in the pathogenesis of ANCA vasculitis.

Antiproteinase 3- and antimyeloperoxidase-associated vasculitis

Antiproteinase 3- and antimyeloperoxidase-associated vasculitis. Wegener's granulomatosis, microscopic polyangiitis, and idiopathic pauci-immune necrotizing crescentic glomerulonephritis (NCGN) are strongly associated with antineutrophil cytoplasmic autoantibodies (ANCAs) directed against either proteinase 3 (anti-PR3) or myeloperoxidase (anti-MPO). This has led some investigators to prefer combining these diseases under the common heading of ANCA-associated vasculitides. However, it is increasingly recognized that there are characteristic differences between patients with anti-PR3 and those with anti-MPO-associated vasculitis. This review focuses on the clinical, histopathologic, and possibly pathophysiologic differences between anti-PR3- and anti-MPO-associated vasculitis. Although there is considerable overlap, the anti-PR3- and anti-MPO-associated vasculitides are each characterized by particular clinical and histopathological findings. Extrarenal organ manifestations and respiratory tract granulomas occur more frequently in patients with anti-PR3 than in those with anti-MPO. Anti-PR3-positive patients with NCGN generally have a more dramatic deterioration of their renal function compared with anti-MPO-positive patients. The term "ANCA-associated vasculitis" is considered as a useful concept in the presence of systemic vasculitis. Likewise, in the presence of vasculitis, the terms "anti-PR3-associated vasculitis" and "anti-MPO-associated vasculitis" are useful concepts.

Anti-neutrophil cytoplasmic antibodies directed against the bactericidal/permeability-increasing protein (BPI) in pediatric cystic fibrosis patients do not recognize N-terminal regions important for the anti-microbial and lipopolysaccharide-binding activity of BPI

This study was performed to examine the prevalence and clinical correlates of bactericidal/permeability-increasing protein anti-neutrophil cytoplasmic antibodies (BPI-ANCA) in pediatric cystic fibrosis (CF) patients and to elucidate their possible role in CF pulmonary pathology. Sera of 27 CF patients were tested for ANCA by indirect immunofluorescence (IFT) and by enzyme-linked immunosorbent assay (ELISA) for ANCA sub-specificities. BPI-ANCA were examined by using standard ELISA for BPI, lipopolysaccharide-binding protein (LBP), and BPI/LBP fusion proteins to epitope map the main binding sites and look for cross-reactivity with LBP. Pulmonary function and serum concentrations of total immunoglobulin G (IgG) were measured and infections were diagnosed. In addition, release of reactive oxygen species (ROS) by neutrophil granulocytes was measured after stimulation with monoclonal BPI-ANCA. Using IFT, two patients showed atypical ANCA staining, six patients exhibited perinuclear ANCA staining, and no cytoplasmic ANCA staining was detected. Of 27 patients, 13 (48%) were BPI-ANCA (IgG) positive, and three were also immunoglobulin A (IgA) BPI-ANCA positive; one patient had ANCA against lactoferrin; and no proteinase 3 ANCA was detected in any of the patients. All BPI-ANCA bound to the C-terminal region of the molecule; none bound to the N-terminus or to LBP. There was no significant correlation between clinical data and the occurrence of BPI-ANCA in this cross-sectional study. Release of ROS from granulocytes was induced by monoclonal BPI-ANCA. Activation of neutrophils and possible modulation of BPI-mediated opsonophagocytosis and disposal of Gram-negative bacteria and lipopolysaccharides by BPI-ANCA raise the possibility that they contribute to pulmonary pathology in pediatric CF patients but intervention longitudinal studies in large groups of patients are needed to establish a causative association.

ANCA-associated glomerulonephritis: Relationship of main ANCA subtypes to renal outcome, age and sex of the patients

BACKGROUND

Antineutrophil cytoplasmic antibodies (ANCA) have been proven to be useful diagnostic tools in patients with systemic vasculitis and glomerulonephritis. These antibodies exist in two types, a cytoplasmic pattern (cANCA) and a perinuclear pattern (pANCA). The effect of the main ANCA subtypes on renal outcome and its relationship to demographic findings and clinical features of patients with ANCA-associated glomerulonephritis has not been adequately studied.

PATIENTS AND METHOD

In this prospective study, we compared the clinical features at presentation and the renal outcome after 1 year of follow-up between two groups of patients with cANCA (n=22) and pANCA (n=29) consecutively encountered over a one-year period.

RESULT

At presentation, rapidly progressive glomerulonephritis (RPGN), and after 1 year of follow-up, endstage renal disease (ESRD) were seen more commonly in patients with pANCA than cases with cANCA (P=0.001 and P=0.004, respectively). Seropositivity for cANCA was more common in male and pANCA in female patients (P=0.005). Occurrence of the pulmonary-renal syndrome or extra-renal manifestations, such as sinusitis and skin rash, did not differ significantly among the two groups of patients with cANCA and pANCA.

CONCLUSION

Patients with pANCA present more frequently with RPGN, leading to a poorer renal survival compared to cases with cANCA. RPGN and pANCA are more common in females.

Antineutrophil cytoplasmic antibodies in Wegener's granulomatosis

The prevalence of antineutrophil cytoplasmic antibodies (ANCA) was studied in 12 children with Wegener's granulomatosis. The serum samples were taken in the active phase of disease and were screened for ANCA by indirect immunofluorescence with normal neutrophils and enzyme linked immunosorbent assay (ELISA) using crude neutrophil extract, proteinase 3, myeloperoxidase, cathepsin G, lactoferrin, and elastase as antigens. Of these 12 patients, 10 wre positive for ANCA in the active phase of their illness, and they showed a predominantly cytoplasmic ANCA staining pattern on indirect immunofluorescence. There were high titres of ANCA directed against crude neutrophil extract, proteinase 3, myeloperoxidase, and cathepsin G. IgM isotypes occurred as commonly as IgG isotypes. Therefore, screening for ANCA is usually but not invariably positive in children with Wegener's granulomatosis. Specific diagnosis still relies on clinical and pathological features, and the value of ANCA in the diagnosis of paediatric Wegener's granulomatosis requires further study.

Wegener's granulomatosis: disease course, assessment of activity and extent and treatment

Wegener's granulomatosis (WG) belongs to the group of necrotizing primary systemic vasculitides of unknown etiology, that are associated with anti-neutrophil cytoplasmic antibodies. The pathological hallmark of WG is the coexistence of vasculitis and granuloma. Due to more sensitive diagnostic instruments, especially ANCA testing, the incidence of diagnosis of WG has risen in the past ten years. Although the precise pathophysiology is not understood yet, there is ample evidence that ANCA, which can lead to cytotoxic reactions in the vascular texture, play a major role, possibly promoted by a dysbalance in the anti-idiotypic network. The clinical disease course is typically two-phasic, beginning with a granulomatous inflammation of the upper respiratory tract, that usually is followed by a generalized vasculitic phase, that can range from mild organ dysfuntion to life threatening multi-organ failure. Consequently, diagnostic procedures, patients' assessment and therapeutic regimens need to be individualized, adapted to stage and activity of the disease as well as standardized.

Use of native and recombinant bactericidal/permeability-increasing proteins (BPI) as antigens for detection of BPI-ANCA

Anti-neutrophil cytoplasmic antibodies (ANCA) against native bactericidal/permeability-increasing protein (nBPI) have gained increasing diagnostic significance in inflammatory bowel disease and cystic fibrosis. However, routine detection of BPI-ANCA requires pure antigen in large quantities. As nBPI is difficult to isolate and is very susceptible to proteolytic cleavage with subsequent epitope loss, it was the aim of this study to determine whether recombinant BPI (rBPI) can be used as an alternative to nBPI as target antigen for ANCA in diagnostic procedures. Therefore, 93 BPI-ELISA-positive sera and controls were compared in different ELISAs using nBPI, rBPI, unglycosylated rBPI and a 21-kDa amino-terminal fragment of rBPI. ELISA results were confirmed by immunoblotting and all sera were tested in indirect immunofluorescence (IFT). There was an 88% (82/93) agreement in recognition of nBPI and rBPI by ANCA in both ELISA systems, yet the quantitation of BPI-ANCA in relative units showed a less optimal result and correlated only by 45% (p < 0.01). Most sera recognized nBPI, rBPI and unglycosylated rBPI equally suggesting that glycosylation has no influence on antigen recognition. Only two sera were positive for the 21-kDa nBPI indicating that the binding sites for ANCA are either conformational epitopes and/or are located mainly on the carboxy-terminal part of the BPI molecule. Most BPI-ELISA-positive sera were negative in IFT (43%), but a perinuclear (pANCA, 30%), a cytoplasmic (cANCA,10%) or an atypical ANCA (aANCA, 2%) staining pattern, as well as a cytoplasmic pattern only on formaldehyde-fixed granulocytes (13%) were also observed. Overall, no characteristic pattern was seen for BPI-ELISA-positive sera in IFT. Taken together, these data suggest that rBPI offers an excellent alternative to nBPI for broad-based BPI-ANCA ELISA and will be of great value in further investigations of BPI-ANCA interactions.

Cloning and functional expression of the murine homologue of proteinase 3: implications for the design of murine models of vasculitis

Anti-neutrophil cytoplasmic autoantibodies recognizing conformational epitopes (c-ANCA) of proteinase 3 (PR3) from azurophil granules are a diagnostic hallmark in Wegener's granulomatosis (WG). Because a functional PR3 homologue has not been identified in rodents, it is difficult to assess immunopathological responses in rats or mice immunized with patients' derived c-ANCA or human PR3. Here we report the full length cDNA cloning and functional expression of murine PR3 in HMC-1 cells. Recombinant murine PR3 shows highly similar substrate specificities towards synthetic peptides and is inhibited by human alpha1-proteinase inhibitor like human PR3. However, neither human c-ANCA, rabbit sera nor mouse monoclonal antibodies to human PR3 recognize the murine homologue. Consequently, it is unlikely that disease observed in mice after immunization with c-ANCA or human PR3 is caused by pathogenic antibodies directed against mouse PR3. Recombinant human-mouse chimaeric variants will be a valuable new tool to localize the disease-specific immunodominant epitopes in human PR3.

Biosynthesis, processing and sorting of neutrophil proteins: insight into neutrophil granule development

Neutrophil granulocytes are specialized phagocytic cells that carry a collection of granules for regulated secretion, each with distinct constituents. The granules can be classified as azurophil (primary), developed first, followed in time by specific (secondary) granules gelatinase granules, and secretory vesicles. Stage- and tissue-specific transcription factors govern the successive expression of genes for granule proteins to allow storage of the gene products in these organelle categories whose packaging is separated in time. Many of the granule proteins, in particular those of the heterogeneous lysosome-like azurophil granules, are subject to extensive post-translational proteolytic processing into mature proteins, most commonly as a post-sorting event. A selective aggregation of proteins destined for storage in granules, as discussed in this review, would facilitate their retention and eliminate a need for distinct sorting motifs on each granule protein. Aggregation of granule proteins, that are often cationic, would be assisted by the anionic serglycin proteoglycans present in neutrophils. The antibacterial granule proteins can serve as models for antibiotics and some of them possess a potentially useful therapeutic ability to bind and neutralize endotoxin. Because aberrant expression of transcription factors regulating the synthesis of granule proteins is often found in leukemia, the clarification of mechanisms regulating the timed expression of granule proteins will shed light on the maturation block in myeloid leukemias.

A comprehensive method to purify three major ANCA antigens: proteinase 3, myeloperoxidase and bactericidal/permeability-increasing protein from human neutrophil granule acid extract

Indirect immunofluorescence (IIF) techniques have shown that anti-neutrophil cytoplasm autoantibodies (ANCA) are useful serological markers for certain small vessel vasculitides and the non-vasculitic inflammatory disorders. ELISA procedures, using purified molecules as solid phase ligands, helped to identify proteinase 3 (PR3) and myeloperoxidase (MPO) as two major ANCA antigens; and recently we characterised bactericidal/permeability-increasing protein (BPI) as another important ANCA antigen. ANCA against these three antigens are associated with different clinical disorders. Therefore purified antigens are needed to determine these different autoantibody specificities in order to help diagnosis and guide treatment. Here we describe a method using Orange-A dye ligand chromatography and cation exchange chromatography for the sequential purification of PR3, MPO and BPI, from the same starting material, an acid extract of normal human neutrophil granules. After separation the three antigens were free of contamination by each other and no traces were found of other known minor ANCA antigens.

The diagnostic and prognostic significance of ANCA

Antineutrophil cytoplasmic antibodies (ANCA) constitute a family of auto-antibodies directed against various components of the neutrophil cytoplasm. Their identification and association with vasculitis and rapidly progressive glomerulonephritis has led to considering these diseases as possible autoimmune disorders. In addition, ANCAs constitute a diagnostic tool and a guideline for therapy during follow-up. Originally identified by Davies et al. in 1982 in 8 patients who had necrotizing glomerulonephritis but no immune deposits or systemic vasculitis (1), ANCA are now regarded as a serological marker for active pauci-immune necrotizing and crescentic glomerulonephritis, either in their renal-limited form or associated with systemic vasculitis such as Wegener's granulomatosis (WG), microscopic polyangiitis (mPA), and Churg-Strauss syndrome (CSS) (2-9). The usefulness of ANCA detection for the diagnosis of these forms of vasculitis is now established but its usefulness on follow-up remains disputed (10-13). Two major ANCA antigens have already been identified. Proteinase 3 (PR3) in a serine protease of 29 kDa initially identified by Kao and producing a cytoplasmic staining pattern termed cANCA by indirect immunofluorescence (IIF) (14,15). Myeloperoxidase (MPO) is another myeloid lysosomal enzyme producing an artefactual perinuclear staining of ethanol-fixed neutrophils termed pANCA (2,16). Both are localized in the azurophilic granules of neutrophils and monocytes, are translocated to the cell surface during cell activation (17), and are able to interact directly with ANCA. Despite this common location, MPO and PR3 are associated with a broad spectrum of clinical conditions.