Antineutrophil cytoplasmic autoantibodies in patients with systemic lupus erythematosus recognize a novel 69 kDa target antigen of neutrophil granules

Causal relationship between primary sclerosing cholangitis and systemic lupus erythematosus: a bidirectional Mendelian randomization study

BACKGROUND

Observational studies have found a link between two autoimmune diseases, namely, primary sclerosing cholangitis (PSC) and systemic lupus erythematosus (SLE). However, the relationship remains unclear.

METHODS

Bidirectional Mendelian randomization (MR) analysis and statistical methods, including inverse variance weighting, weighted median, and MR-Egger tests, were performed using data from genome-wide association studies to detect a causal relationship between PSC and SLE. Sensitivity analyses were subsequently performed to assess the robustness of the results. Univariate MR methods were also investigated.

RESULTS

Results of MR analysis suggested that PSC was associated with an increased risk for SLE (odds ratio: 1.33, 95% confidence interval: 1.10-1.61, P=0.0039) However, SLE had no significant causal relationship with PSC.

CONCLUSION

Results of MR analysis revealed that patients with PSC were at an increased risk for SLE, which provides new insights into the relationship between these two autoimmune diseases.

ANCA in patients with systemic lupus erythematosus. A cross sectional study in Brazilian patients and review of literature

BACKGROUND

Antineutrophil cytoplasmatic antibodies (ANCA) have been detected in patients with systemic lupus erythematosus (SLE). In this study, we investigated the presence of ANCA in a sample of Brazilian SLE patients and its possible associations with clinical and serological outcomes. Additionally, we reviewed the literature of on ANCA in SLE.

RESULTS

The presence of ANCA was detected in 130 patients using indirect immunofluorescence (IIF). The test was positive in 29.9% of the cases (17.6% pANCA and 11.5% cANCA). Male sex and peripheral vasculitis were more prevalent in the ANCA-positive sample. cANCA was associated with lupus anticoagulant and pANCA had a positive association with peripheral vasculitis and a negative association with anti- SSB/La antibodies. In the 22 studies included in the literature review, a wide range of ANCA positivity was found (13% to 81.1% by IIF and 0 to 22.2% by ELISA). ANCA was associated with renal damage in the Asian population. Although other associations have been found in isolated studies, they were not consistently reported.

CONCLUSIONS

The ANCA prevalence found in this Brazilian sample was within the range reported in the literature and these autoantibodies were more frequent in males and in patients with vasculitis. The literature showed controversial results on the association between ANCA and SLE disease activity or clinical characteristics.

Clinicopathologic Characteristics and Outcomes of Lupus Nephritis With Antineutrophil Cytoplasmic Antibody: A Retrospective Study

Few studies have analyzed the clinicopathologic characteristics and outcomes of lupus nephritis (LN) patients with antineutrophil cytoplasmic antibody (ANCA). The clinical and renal histopathologic data of 154 patients with biopsy-proven LN from 2011 to 2013 were analyzed retrospectively. The patients were followed up for a median period of 16.8 ± 9.4 months, and their outcomes were analyzed. Multivariate Cox analysis was used to evaluate the independent factors for poor outcomes. Among the 154 LN patients, 26 (16.88%) were seropositive for ANCA. The incidences of alopecia, oral ulcer, photosensitivity and skin lesion, and psychosomatic manifestations in the ANCA-positive group were significantly higher than in the ANCA-negative group (P = 0.007, 0.02, 0.02, and 0.03, respectively). Compared with the ANCA-negative group, the ANCA-positive group had significantly lower levels of complement C3 (P = 0.03). Additionally, the positive rate of antinucleosome antibodies, antihistone antibodies, antimitochondrial antibody M2, and anticardiolipin antibodies were higher significantly in the ANCA-positive patients than in the ANCA-negative patients (P = 0.001, 0.001, 0.03, 0.005, respectively). The ANCA-positive group had a notably higher chronic index than the ANCA-negative group (P = 0.01). During the follow-up, the complete remission rate in the ANCA-negative group was higher than that in the ANCA-positive group (P = 0.01). The cumulative renal survival rate in the ANCA-positive group was significantly lower than in the ANCA-negative group (log-rank = 6.59, P = 0.01). Multivariate Cox analysis revealed that the reduced estimated glomerular filtration rate (HR, 1.02; 95% confidence interval, 1.01 to 1.03; P = 0.005), NLR (HR, 1.20; 95% confidence interval, 1.02 to 1.40; P = 0.03), and ANCA (HR, 3.37; 95% confidence interval, 1.12 to 10.09; P = 0.03) were independent risk factors for patients' renal survival after adjusting for age, sex, crescent formation, and glomerulosclerosis. The study found ANCA in LN patients is not rare, and patients with ANCA present with more severe clinicopathologic injuries. Thus, ANCA is an independent risk factor for poor renal outcomes in LN patients.

Detection and analysis of autoantigens targeted by autoantibodies in immunorelated pancytopenia

Previously, we described a group of patients with hemocytopenia who did not conform to diagnostic criteria of known hematological and nonhematological diseases. Most patients responded well to adrenocortical hormone and/or high-dose intravenous immunoglobulin treatment, indicating that cytopenia might be mediated by autoantibodies. Autoantibodies were detected on the membrane of various bone marrow (BM) hemopoietic cells by bone marrow mononuclear-cell-Coombs test or flow cytometric analysis. Thus, the hemocytopenia was termed "Immunorelated Pancytopenia" (IRP) to distinguish it from other pancytopenias. Autoantigens in IRP were investigated by membrane protein extraction from BM hemopoietic cells and BM supernatant from IRP patients. Autoantibody IgG was detected in the BM supernatant of 75% of patients (15/20), which was significantly higher than that in aplastic anemia, myelodysplastic syndrome, or autoimmune hemolytic anemia patients (0%) and normal healthy controls (0%) (P < 0.01). Autoantigens had approximate molecular weights of 25, 30, 47.5, 60, 65, 70, and 80 kDa, some of which were further identified by mass fingerprinting. This study identified that a G-protein-coupled receptor 156 variant and chain P, a crystal structure of the cytoplasmic domain of human erythrocyte band-3 protein, were autoantigens in IRP. Further studies are needed to confirm the antigenicity of these autoantigens.

Autoantibodies in primary sclerosing cholangitis

The aetiology of primary sclerosing cholangitis (PSC) is not known and controversy exists as to whether PSC should be denominated an autoimmune disease. A large number of autoantibodies have been detected in PSC patients, but the specificity of these antibodies is generally low, and the frequencies vary largely between different studies. The presence of autoantibodies in PSC may be the result of a nonspecific dysregulation of the immune system, but the literature in PSC points to the possible presence of specific antibody targets in the biliary epithelium and in neutrophil granulocytes. The present review aims to give an overview of the studies of autoantibodies in PSC, with a particular emphasis on the prevalence, clinical relevance and possible pathogenetic importance of each individual marker.

Non-DNA-Binding Antibodies in Patients with Lupus Nephritis Could Recognize Membrane Proteins of Glomerular Mesangial Cells

Lupus nephritis (LN) is a prototypic autoimmune disease, however, the precise immuno-pathogenesis of LN remains to be elucidated. In our previous studies, autoantibodies against mesangial cells had been identified in sera from patients with lupus nephritis and could bind the membrane proteins of human mesangial cells (HMC) directly through antigen-antibody interaction without DNA bridge. The current study is to investigate whether the autoantibodies were associated with anti-DNA antibodies and their target antigens distribution in different cell types. Sera from nine patients with renal biopsy proven lupus nephritis with positive anti-dsDNA antibodies and four healthy subjects were collected. IgG was isolated by Protein G affinity chromatography and then non-DNA-binding IgG fractions were obtained after deletion of anti-DNA antibodies using a DNA-cellulose affinity column. Membrane proteins, obtained from HMC, human umbilical vein endothelial cells (HUVEC), peripheral mononuclear cells by sonication and sequential centrifugation, were solubilized and applied in Western-blot analysis to characterize the target antigens. In results, the non-DNA-binding IgG fractions from sera of patients with lupus nephritis could blot the protein(s) of HMC membrane at 74, 63, and 42 kD. However, only a similar 74-kD protein could be blotted on membrane of HUVEC, and the target antigens on membranes of mononuclear cells were heterogeneous. In conclusion, our preliminary study had demonstrated that non-DNA binding autoantibodies against mesangial cells could be found in sera from patients with lupus nephritis. Although the target antigens might not be cell specific, the roles of these autoantibodies in the pathogenesis of lupus nephritis need further investigation.