Prevalence and clinical significance of anti-lactoferrin autoantibodies in inflammatory bowel diseases and primary sclerosing cholangitis

The Multifaceted Effects of Alpha1-Antitrypsin on Neutrophil Functions

Neutrophils are the predominant immune cells in human blood possessing heterogeneity, plasticity and functional diversity. The activation and recruitment of neutrophils into inflamed tissue in response to stimuli are tightly regulated processes. Alpha1-Antitrypsin (AAT), an acute phase protein, is one of the potent regulators of neutrophil activation via both -protease inhibitory and non-inhibitory functions. This review summarizes our current understanding of the effects of AAT on neutrophils, illustrating the interplay between AAT and the key effector functions of neutrophils.

Gene-Specific DNA Methylation Changes Predict Remission in Patients with ANCA-Associated Vasculitis

ANCA-associated vasculitis is an autoimmune condition characterized by vascular inflammation and organ damage. Pharmacologically induced remission of this condition is complicated by relapses. Potential triggers of relapse are immunologic challenges and environmental insults, both of which associate with changes in epigenetic silencing modifications. Altered histone modifications implicated in gene silencing associate with aberrant autoantigen expression. To establish a link between DNA methylation, a model epigenetic gene silencing modification, and autoantigen gene expression and disease status in ANCA-associated vasculitis, we measured gene-specific DNA methylation of the autoantigen genes myeloperoxidase (MPO) and proteinase 3 (PRTN3) in leukocytes of patients with ANCA-associated vasculitis observed longitudinally (n=82) and of healthy controls (n=32). Patients with active disease demonstrated hypomethylation of MPO and PRTN3 and increased expression of the autoantigens; in remission, DNA methylation generally increased. Longitudinal analysis revealed that patients with ANCA-associated vasculitis could be divided into two groups, on the basis of whether DNA methylation increased or decreased from active disease to remission. In patients with increased DNA methylation, MPO and PRTN3 expression correlated with DNA methylation. Kaplan-Meier estimate of relapse revealed patients with increased DNA methylation at the PRTN3 promoter had a significantly greater probability of a relapse-free period (P<0.001), independent of ANCA serotype. Patients with decreased DNA methylation at the PRTN3 promoter had a greater risk of relapse (hazard ratio, 4.55; 95% confidence interval, 2.09 to 9.91). Thus, changes in the DNA methylation status of the PRTN3 promoter may predict the likelihood of stable remission and explain autoantigen gene regulation.

Neutrophil anti-neutrophil cytoplasmic autoantibody proteins: bactericidal increasing protein, lactoferrin, cathepsin, and elastase as serological markers of inflammatory bowel and other diseases

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract comprising Crohn's disease and ulcerative colitis. Although the pathogenesis of the disease is not clearly defined yet, environmental, genetic and other factors contribute to the onset of the disease. Apart from the clinical and histopathological findings, several serological biomarkers are also employed to detect IBD. One of the most thoroughly studied biomarker is anti-neutrophil cytoplasmic autoantibody (ANCA). We herein provide an overview of the current knowledge on the use of ANCA and certain ANCA proteins, such as bactericidal increasing protein, lactoferrin, cathepsin G and elastase, as serological markers for IBD and other diseases.

Tumor necrosis factor-α driven inflammation in alpha-1 antitrypsin deficiency: a new model of pathogenesis and treatment

Alpha-1 antitrypsin (AAT) deficiency (AATD) has traditionally been thought of as a genetic disorder characterized by lung destruction and early emphysema in a low AAT, and high neutrophil elastase (NE) environment in the lungs of affected individuals. Recently, a growing body of evidence has emerged to support the hypothesis that tumor necrosis factor alpha (TNF-α) is essential in the pathogenesis of both genetic AATD and non-genetic chronic obstructive pulmonary disease (COPD). Reports have highlighted the importance of TNF-α driven immune cell dysfunction in the development of lung disease in AATD. The authors discuss the role of AAT as a key modulator of TNF-α signaling firstly in the setting of AATD and secondly in other conditions where AAT augmentation therapy has potential utility as a novel therapy.

The circulating proteinase inhibitor α-1 antitrypsin regulates neutrophil degranulation and autoimmunity

Pathological inflammation and autoimmune disease frequently involve elevated neutrophil activity in the absence of infectious agents. Tumor necrosis factor-α (TNF-α) contributes to many of the problems associated with autoimmune diseases. We investigated the ability of serum α-1 antitrypsin (AAT) to control TNF-α biosynthesis and signaling in neutrophils and assessed whether AAT deficiency (AATD) is a TNF-α-related disease. In vitro studies demonstrate that serum AAT coordinates TNF-α intracellular signaling and neutrophil degranulation of tertiary and secondary granules via modulation of ligand-receptor interactions. AATD patients homozygous for the Z allele were characterized by increased activation of the TNF-α system, as demonstrated by increased membrane TNF-α levels and increased plasma concentrations of TNF receptor 1 and neutrophil-released secondary and tertiary granule proteins. The incidence of autoantibodies directed against degranulated lactoferrin and surface protein accessible to these antibodies was increased in ZZ-AATD, leading to an enhanced rate of neutrophil reactive oxygen species production. Treatment of ZZ-AATD individuals with AAT augmentation therapy resulted in decreased membrane TNF-α expression and plasma levels of granule antigenic proteins and immunoglobulin G class autoantibodies. These results provide a mechanism by which AAT augmentation therapy affects TNF-α signaling in the circulating neutrophil, indicating promising potential of this therapy for other TNF-α-related diseases.

Evaluation of the combined application of ethanol-fixed and formaldehyde-fixed neutrophil substrates for identifying atypical perinuclear antineutrophil cytoplasmic antibodies in inflammatory bowel disease

No clear guidelines for indirect immunofluorescence (IIF) detection and interpretation of antineutrophil cytoplasmic antibodies (ANCA) have been proposed for inflammatory bowel diseases (IBD). We evaluated the reliability of the combined use of ethanol- and formalin-fixed neutrophil substrates to identify atypical perinuclear ANCA (P-ANCA) by IIF under routine laboratory circumstances. A total of 204 IBD patients were assessed with four different fluorescent substrates in two distinct laboratories. Antibodies against myeloperoxidase, proteinase-3, and other specific granule proteins (elastase, lactoferrin, cathepsin G, lysozyme, and bactericidal permeability-increasing protein) were measured by an enzyme-linked immunosorbent assay. The combined application of ethanol- and formalin-fixed slides to detect atypical P-ANCA resulted in a lack of agreement between assays (kappa, < or =0.39) in the interassay study and moderate agreement in the interobserver study (kappa, 0.42). After atypical and typical P-ANCA patterns were combined, the consensus improved greatly. A total of 26.9% of patients were P-ANCA positive by at least two tests (44.3% of ulcerative colitis [UC] and 13.1% of Crohn's disease [CD] patients; P < 0.0001), while overall ANCA positivity was 22.5% to 34.8%. The combined application of ethanol-fixed and formaldehyde-fixed neutrophil substrates did not facilitate differentiation between P-ANCA and atypical P-ANCA, and the results were not consistent when substrates from different sources were used. Combining all P-ANCA ensures the highest sensitivity and specificity in differentiating UC from CD.

Antineutrophil cytoplasmic antibodies in Bulgarian patients with rheumatoid arthritis: characterization and clinical associations

OBJECTIVE

The aim of this study was to study the prevalence, subspecificities, and immunoglobulin (Ig)G subclass distribution of antineutrophil cytoplasmic antibodies (ANCA) in 90 Bulgarian patients with rheumatoid arthritis (RA) and to investigate the clinical associations of ANCA in these patients.

METHODS

The ANCA were detected by indirect immunofluorescence, while antigen specificities were determined by enzyme-linked immunosorbent assay (ELISA) directed against myeloperoxidase (MPO), proteinase 3 (PR3), bactericidal/permeability-increasing protein (BPI), lactoferrin (LF), leukocyte elastase (LE), and cathepsin G (CG). The IgG subclass reactivity of antibodies to BPI and LF was measured.

RESULTS

Antineutrophil cytoplasmic antibodies were found in 18 RA patients. Only a P-ANCA fluorescence pattern was seen. Six sera reacted to BPI, five to LF, one to MPO, one to PR3, and one to CG by ELISA testing. Immunoglobulin-G1 was the predominant subclass for LF-ANCA, whereas IgG1/3 contributed mainly to BPI-ANCA. Compared to P-ANCA-negative RA patients, the P-ANCA-positive patients exhibited significantly higher inflammatory activity, as estimated by disease activity score, C-reactive protein, erythrocyte sedimentation rate, and higher levels of IgM rheumatoid factor.

CONCLUSION

Twenty percent of Bulgarian patients with RA have P-ANCA in their sera. These antibodies are directed against variable antigen specificities, while ANCA positivity in RA reflects disease and inflammatory activity.

Aetiopathogenesis of primary sclerosing cholangitis

The aetiology and pathogenesis of PSC have not yet been clearly defined. The hypothesis that PSC is an immune mediated disease is supported by associations with HLA haplotypes, the presence of autoantibodies, increased levels of total serum immunoglobulins and the association with other autoimmune diseases. PSC does not, however, have many of the characteristics of classical autoimmunity, particularly the usual female preponderance of disease and lack of a good response to immunosuppression. Non-immune mechanisms such as bacterial infection, ischaemia and toxicity are also clearly important in the development of the disease and these factors may trigger peribiliary inflammation and cytokine-induced hepatic fibrosis. PSC may be triggered in genetically susceptible individuals by toxic or infectious agents gaining access to the liver via a diseased and permeable colon.

Anti-neutrophil antibodies in primary sclerosing cholangitis

Anti-neutrophil specific antibodies are detected in up to 88% of patients with PSC. The labelling pattern of neutrophils produced by these antibodies when examined by indirect immunofluorescence microscopy is distinct from that produced by anti-neutrophil cytoplasmic antibodies (ANCA) in vasculitic diseases. The antigen(s) recognized by anti-neutrophil antibodies in PSC is not yet known but appears to be localized to the periphery of the nucleus. Accordingly, the term peripheral anti-neutrophil nuclear antibodies (p-ANNA) is more appropriate than the frequently used p-ANCA. As the titre of p-ANNA in PSC does not correlate with disease-specific clinical parameters, they are not useful markers for the management of patients. However, the high prevalence of p-ANNA in PSC makes them a reasonable diagnostic marker if used in conjunction with other standard diagnostic tests. The role of anti-neutrophil antibodies in the pathogenesis of PSC, if any, remains to be established.

Antilactoferrin antibodies in autoimmune liver disease

Antilactoferrin antibodies have been reported in patients with several autoimmune disorders, including primary biliary cirrhosis, autoimmune hepatitis and autoimmune cholangitis. We investigated the prevalence and the clinical significance of such autoreactivity in patients with autoimmune and viral chronic liver disease. Sera from 39 patients with autoimmune hepatitis, 51 with primary biliary cirrhosis, 17 with autoimmune cholangitis, 24 with primary sclerosing cholangitis and 28 with HCV-related chronic hepatitis were studied. Positivity for antilactoferrin antibodies was evaluated by Western immunoblotting with purified human lactoferrin. Antilactoferrin antibodies were detected more often in autoimmune liver disorders (25% autoimmune hepatitis, 25% primary biliary cirrhosis, 35% autoimmune cholangitis, 29% primary sclerosing cholangitis) than in HCV-related chronic hepatitis (3.5%, P < 0.02 versus all). Positivity for antilactoferrin antibodies was not associated with a particular clinical or biochemical profile of the underlying liver disease. No correlation was observed between antilactoferrin reactivity and perinuclear antineutrophil cytoplasmic antibodies. Antilactoferrin antibodies are present significantly more often in autoimmune than in viral liver disorders, but they cannot be considered the serological marker of a specific autoimmune liver disease.