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

Antineutrophil cytoplasmic antibody is an independent risk factor in rheumatoid arthritis-associated interstitial lung disease

OBJECTIVES

This study aimed to investigate the clinical relevance of antineutrophil cytoplasmic antibody (ANCA) in patients with rheumatoid arthritis-associated interstitial lung disease (RA-ILD).

METHODS

Detailed clinical records of rheumatoid arthritis (RA) patients who underwent ANCA screening tests were collected. ANCA measurements were determined by indirect immunofluorescence assay (IIF) and enzyme-linked immunosorbent assay (ELISA). Clinical characteristics were compared between ANCA-positive and ANCA-negative groups, and multivariable logistic models were used to evaluate the independent association of ANCA with ILD in RA patients.

RESULTS

The prevalence of ANCA by IIF was significantly higher in RA-ILD patients compared to those with RA without ILD (31.7 % vs. 19.5 %, p < 0.001). RA-ILD patients positive for ANCA exhibited elevated levels of inflammatory markers and greater disease activity, and showed more severe impairment of lung function compared to ANCA-negative RA-ILD patients. Multivariable logistic regression analysis revealed an independent association of ANCA, especially pANCA, with RA-ILD. ANCA specificities for BPI, elastase, and cathepsin-G were found in 15.6 % of RA-ILD patients; the specificities for most others remain unknown.

CONCLUSIONS

The findings suggest a potential role for ANCA/pANCA in stratifying the risk of RA and provide supplementary information to the existing clinically available assays. This additional information may be valuable in identifying RA patients who require further investigations for RA-ILD, such as high-resolution computed tomography (HRCT). These results emphasize the potential clinical relevance of ANCA in the context of RA-ILD.

"NETtling" the host: Breaking of tolerance in chronic inflammation and chronic infection

How and why we break tolerance to self-proteins still remains a largely unanswered question. Neutrophils have been identified as a rich source of autoantigens in a wide array of autoimmune diseases that arise as a consequence of different environmental and genetic factors, e.g. rheumatoid arthritis (RA), lupus, vasculitis, cystic fibrosis (CF) etc. Specifically, neutrophil extracellular trap (NET) formation has been identified as a link between innate and adaptive immune responses in autoimmunity. Autoantigens including neutrophil granular proteins (targeted by anti-neutrophil cytoplasmic antibodies, ANCA) as well as post-translationally modified proteins, i.e. citrullinated and carbamylated proteins targeted by anti-citrullinated protein antibodies (ACPA) and anti-carbamylated protein antibodies (ACarPA), respectively, localize to the NETs. Moreover, NETs provide stimuli to dendritic cells that potentiate adaptive autoimmune responses. However, while NETs promote inflammation and appear to induce humoral autoreactivity across autoimmune diseases, the antigen specificity of autoantibodies found in these disorders is striking. These unique autoantigen signatures suggest that not all NETs are created equal and that the environment in which NETs arise shapes their disease-specific character. In this review article, we discuss the effects of different stimuli on the mechanism of NET formation as well as how they contribute to antigen specificity in the breaking of immune tolerance. Specifically, we compare and contrast the autoreactive nature of NETs in two settings of chronic airway inflammation: one triggered by smoking, a recognized environmental NET stimulus in RA patients, and one mediated by Pseudomonas aeruginosa, the most prevalent lung pathogen in CF patients. Finally, we draw attention to novel findings that, together with the specific environmental/chemical stimuli, should be taken into account when investigating how and why antigen specificity arises in the context of NET formation.

Antineutrophil cytoplasmic antibodies against myeloperoxidase, proteinase 3, elastase, cathepsin G and lactoferrin in Japanese patients with rheumatoid arthritis

Antineutrophil cytoplasmic antibodies (ANCAs) against myeloperoxidase (MPO), proteinase 3 (PR-3), lactoferrin (LF), cathepsin G (CG) and elastase (EL) were determined to investigate whether the presence of ANCAs is closely related to extra-articular manifestations in Japanese patients with rheumatoid arthritis (RA). Antibodies against MPO, PR-3, LF, CG and EL were determined in sera from 125 patients with RA and 83 sera from patients with other rheumatic diseases by enzyme-linked immunosorbent assay. Clinical manifestations and laboratory parameters of the patients were studied from medical records. Thirty of the 125 (24.0%) RA patients were positive for ANCAs for at least one of these 5 ANCA antigens. Among the 5 ANCAs, anti-LF antibody (anti-LF) (16.8%) was most commonly observed in patients with RA. A higher joint score (JS) and an elevated ESR were demonstrated in ANCA-positive RA patients compared to those of ANCA-negative patients (40.8 ± 43.3, 24.3 ± 26.2, p < 0.05, 44.4 ± 22.4, 28.9 ± 23.6, p < 0.05, respectively). No statistical differences in the presence of interstitial pneumonia, cutaneous vasculitis, rheumatoid nodules and mononeuropathy multiplex were observed between ANCA-positive and ANCA-negative patients. The presence of anti-LF is expected to be of pathological relevance, as the action of anti-LF towards LF results in the inhibition of the anti-inflammatory activity of LF.

Anti-neutrophil cytoplasmic autoantibodies against bactericidal/permeability-increasing protein in patients with rheumatoid arthritis and their correlation with bronchial involvement

Anti-neutrophil cytoplasmic autoantibodies against bactericidal/permeability-increasing protein (BPI-ANCA) are known to be present in patients with cystic fibrosis, diffuse panbronchiolitis, and inflammatory bowel disease, especially in relation to chronic Gram-negative bacterial infection. To investigate the possible role of BPI-ANCA in rheumatoid arthritis (RA), we measured the serum titer of BPI-ANCA and examined clinical manifestations, including pulmonary complications, in patients with RA. Seventy-four RA patients were recruited to our study. The titer of BPI-ANCA was measured by enzyme-linked immunosorbent assay (ELISA). Pulmonary complications were evaluated using high-resolution computed tomography (HRCT), which revealed 26 patients with bronchial diseases (BD group), 25 with interstitial pneumonia (IP group), and 23 without any particular lung lesion (normal group). The correlations between the titer of BPI-ANCA and patients' clinical and laboratory findings were then analyzed. The numbers of tender joints, swollen joints, and the Disease Activity Score including 28 joint count were significantly higher in the BD group. The titer of BPI-ANCA was positively correlated with age, erythrocyte sedimentation rate (ESR), and bronchial involvement in all subjects. Stepwise multiple regression analysis of factors affecting the titer of BPI-ANCA selected ESR and bronchial involvement as independent variables. Our results show that BPI-ANCA was positively correlated with chronic inflammatory status in RA patients, and we is believe it is positively linked with bronchial diseases.

Anti-myeloperoxidase and anti-cathepsin G antibodies in sulphonamide hypersensitivity

BACKGROUND

Anti-neutrophil cytoplasmic antibodies (ANCA) are associated with vasculitis in humans. Sulphonamide antimicrobials cause drug hypersensitivity (HS) reactions with some clinical signs that are suggestive of vasculitis.

OBJECTIVE

The purpose of this study was to determine whether sulphonamide HS is associated with anti-neutrophil antibodies, using the dog as a spontaneous clinical model.

METHODS

Thirty-four sulphonamide-HS dogs, 11 sulphonamide-'tolerant' dogs, and nine healthy sulphonamide-naïve dogs were evaluated for anti-neutrophil antibodies using a commercial ELISA against human myeloperoxidase (MPO), a commercial human ANCA Western blot protocol, and immunoblotting against whole canine neutrophils.

RESULTS

Using ELISA, anti-MPO antibodies were found with an apparent higher frequency in HS dogs (50%), compared with 'tolerant' dogs (18%), which also showed significantly lower absorbances. Among HS dogs, anti-MPO antibodies were significantly more common, with significantly higher absorbances, in dogs that did not survive the HS reaction (78%) compared with survivors (35%). Using immunoblotting, ANCA were detected with similar overall frequencies in HS and 'tolerant' dogs. However, one protein targeted by several HS dogs, but no 'tolerant' dogs, was identified as cathepsin G.

CONCLUSION

These data indicate that anti-MPO antibodies and anti-cathepsin G antibodies are associated with sulphonamide HS. Anti-MPO antibodies have been shown to be pathogenic both in vitro and in vivo, leading to vasculitis lesions and vasculitis-like syndromes. The present study therefore suggests that vasculitis might be one mechanism of tissue damage in this sulphonamide HS. Furthermore, the evaluation of ANCA, and its relationship to disease severity and clinical outcome, should be considered in human patients with sulphonamide drug HS.

Antibodies to selected minor target antigens in patients with anti-neutrophil cytoplasmic antibodies (ANCA)

In patients with anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis, indirect immunofluorescence (IF) distinguishes between cytoplasmic (C-ANCA) and perinuclear (P-ANCA) neutrophil staining patterns. In patients with primary systemic vasculitis such as Wegener's granulomatosis, microscopic polyangiitis and Churg-Strauss syndrome, these IF staining patterns correspond broadly with antibodies to the two major antigens: the C-ANCA pattern is associated generally with antibodies to serine protease 3 (PR3) and the P-ANCA pattern with antibodies to myeloperoxidase (MPO). However, some sera positive for ANCA by IF are negative for anti-PR3 and anti-MPO antibodies, suggesting the presence of antibodies to minor antigens of PMN granules. We tested sera from a previously well-defined clinical cohort of patients for antibodies to four possible minor antigens: bactericidal permeability increasing protein, elastase, cathepsin G and lactoferrin. IF-positive (+) sera had significantly higher antibody frequencies to the minor antigens than did the IF-negative (-) sera (P < 0.01). Patients with IF(+) PR3(-)MPO(-) sera showed the most varied reactivity to the minor antigens. Among the IF(+) groups, the IF(+) PR3(+)/MPO(-) sera showed the lowest reactivity to the minor antigens. Patients with well-defined ANCA specificities, e.g. the PR3-ANCA response associated with Wegener's granulomatosis, are less likely than are other patient subsets to have antibodies to minor antigen targets. Autoantibodies to these minor antigens contribute to the overall pattern of ANCA identified by IF and help to explain why the correlation between IF and enzyme immunoassays show discrepancies. While the pathophysiological significance of antibodies to minor target antigens needs further evaluation, they may be markers of inflammation associated with disease processes.

Anticuerpos anticitoplasma de neutrófilo en enfermedades distintas a las vasculitis idiopáticas: correlaciones clínicas y especificidades antigénicas

The value of antineutrophil cytoplasmic antibodies (ANCA) in the diagnosis of several types of idiopathic vasculitis has been well-documented: In these diseases the ANCA show two classical immunofluorescence patterns, C-ANCA and P-ANCA, which have antigen specificity for the myeloperoxidase and proteinase 3, respectively. However, the appearance of ANCA in very different diseases other than the mentioned vasculitis, has been documented in recent years. In these diseases, the ANCA generally have atypical immunofluorescence patterns and are directed against neutrophil antigens that are different from the previous two, their clinical value still being under debate.