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Objectives Inhibitory FcγRIIB/CD32B on B cells are critical for immunity regulation to help maintain peripheral tolerance. Altered FcγRIIB expression on B cells has been observed in several autoimmune diseases, and animal studies have suggested that FcγRIIB on B cells participates in the pathogenesis of ANCA-associated vasculitis (AAV). Here, we investigated the expression of FcγRII (FcγRIIB) on various B cell subsets and the correlation of FcγRII/CD32 expression with disease activity in AAV patients. Material and methods Blood samples of patients with AAV in active stage and in remission were collected. FcγRII/CD32 expressions on various B cell subsets of the whole blood were detected by flow cytometry, and their correlation with clinical and pathological data was analysed. Results The expression of FcγRII/CD32 on plasma cells was significantly lower in AAV patients in active stage than those in both AAV patients in remission and healthy donors. Furthermore, the expression of FcγRII/CD32 on plasma cells negatively correlated with BVAS and percentages of cellular crescents in renal biopsies. Conclusions There is a down-regulation of FcγRIIB/CD32B expression on B cells in patients with AAV, which is associated with the disease activity of AAV.

ObjectivesAnti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of life-threatening autoimmune diseases. Inhibitors of apoptosis proteins (IAPs) are a class of molecules engaged in cell death and inflammation, interventions of which are proven effective in a number of inflammatory diseases. Here we tested whether targeting IAPs could ameliorate AAV and explored the potential mechanism.MethodsWe collected 19 kidney specimens from patients with myeloperoxidase (MPO)-AAV to investigate the expression of IAPs. The IAP pan-inhibitor SM164 was used to treat the experimental autoimmune vasculitis (EAV) rat model of AAV. RNA sequencing of renal cortex and enrichment analysis were developed to interpret gene expression. Functional experiments were performed to investigate the role of SM164 on neutrophils and endothelial cells.ResultsThe expression of three IAPs (cIAP1, cIAP2 and XIAP) was upregulated in kidneys of AAV patients compared with normal controls. SM164 dramatically reduced renal injury in EAV rats. Transcriptomic analysis revealed prominent alterations in fatty acid oxidation and respiratory burst following SM164 treatment. Functional studies demonstrated that SM164 inhibited neutrophil activation induced by MPO-ANCA positive IgG or serum from MPO-AAV patients, and such inhibitory effect was abolished by gene silencing or pharmacological inhibition of fatty acid oxidation. SM164 also inhibited the adhesion of neutrophils to endothelial cells with little effect on the endothelial injury induced by serum from MPO-AAV patients.ConclusionInhibition of IAPs with SM164 played a protective role in AAV through enhancing intracellular fatty acid oxidation in neutrophils.

Objective The biological functions of the platelets contributing to ANCA-associated vasculitis (AAV) are largely unclear. The current study aimed to investigate the potential role of platelet-derived microparticles (PMPs) in AAV. Methods In the current study, microparticles in AAV patients were analysed by flow cytometry, and PMPs were probed for relative levels of 640 bioactive proteins secreted from patients’ platelets using antibody microarrays. These data were then correlated with clinical and pathological parameters. Results PMPs were significantly increased in 69 AAV patients, predominantly MPO-ANCA positive patients in active stage compared with in remission [4406.8/μl (2135.4, 5485.0) vs 549.7/μl (350, 708.5), P < 0.0001], and 43% of microparticles in active AAV were PMPs. Compared with 15 patients in remission, highly expressed proinflammatory molecules in the microparticles from platelets in 15 AAV patients in active stage revealed that potential functions of PMPs were promotion of the effect of chemotaxis, adhesion, growth and apoptosis (all the patients for array analysis were MPO-ANCA positive). The level of PMPs had a significant association with disease activity, inflammation, and renal damage. Conclusion PMPs may serve as inflammatory propagators through their wide production of proinflammatory cytokines in AAV, potentially providing a novel therapeutic target.

Objective The interaction between neutrophils and activation of alternative complement pathway plays a critical role in the pathogenesis of ANCA-associated vasculitis (AAV). MPO, which can be released from ANCA-stimulated neutrophils, was recently demonstrated to be capable of activating the alternative complement pathway. Here we aimed to investigate the interaction between MPO and factor H (FH), a key regulator of the alternative pathway, and its effect on the functional activities of FH. Methods Detection of FH and MPO on neutrophil extracellular traps (NETs) induced by serum from AAV patients and in kidney biopsies of AAV patients was performed by immunostaining. In vitro binding between MPO and FH was examined by ELISA and surface plasmon resonance. The influence of MPO on the complement regulatory activity of FH was further assessed. Results FH deposited and co-localized with MPO in NETs. In kidney biopsies from AAV patients, MPO was closely adjacent to FH in glomerular capillaries. We demonstrated that MPO binds to FH with an apparent nanomolar affinity and identified short consensus repeats 1-4 of FH as the major binding sites. In terms of functional analysis, MPO inhibited the interaction between FH and C3b and the decay-accelerating activity of FH. The fluid phase and surface cofactor activities of FH upon C3b inactivation were inhibited by MPO. Conclusion Our findings indicate that MPO binds to FH and influences the complement regulatory activity of FH. MPO-FH interaction may participate in the pathogenesis of AAV by contributing to activation of the alternative complement pathway.

Objective The podocyte lesion in LN is still an intriguing controversy. We assess the associations between podocyte lesions and clinico-pathological features in a large cohort of LN patients. Methods The clinico-pathological data of 202 patients with renal biopsy-proven LN were retrospectively studied. The degree of podocyte lesions was assessed morphologically and its correlations with clinico-pathological parameters were further analysed. Results The podocyte foot processes of most LN patients significantly effaced, reflected by the median foot process width (FPW) of 1397.39 nm, and 13 patients met the histological criteria of lupus podocytopathy. The FPW was correlated with proteinuria (r = 0.509, P 1240 nm, could differentiate nephrotic proteinuria from non-nephrotic proteinuria with sensitivity 81.5% and specificity 62.7%. The FPW varied significantly with different types of LN, and the patients with combined LN presented with the most severe lesions. The complete remission rate was significantly higher and the long-term renal outcome was better in the group with calcineurin inhibitors than that with other regimens in patients with FPW >1240 nm. Conclusion Podocyte damage was common in LN. Pure lupus podocytopathy might act as an extreme form of lupus podocyte lesion, and more patients might present with severe podocyte effacement concealed in different types of LN, which needs further investigation.

OBJECTIVE The aim of this study was to investigate serum complement factor H (CFH) and its associations with clinical and pathological features in patients with LN. METHODS Serum CFH was detected in 241 LN patients, 38 active and 11 inactive patients with SLE without clinical evidence of renal involvement and 51 normal controls. Serum CFH autoantibodies and CFH Tyr402His were screened in the 241 LN patients. CFH deposition in kidneys was detected in some patients. RESULTS Serum CFH levels in patients with LN at active phase were significantly lower than in 38 SLE patients or in normal controls. No serum anti-CFH autoantibodies were detected in patients with LN, and there was no significant difference in CFH Tyr402His distribution between patients with LN and normal controls. Glomerular expression of CFH was stronger than in normal controls. Serum CFH levels were mildly negatively associated with SLEDAI scores (r = -0.204, P = 0.001) and positively associated with serum C3 (r = 0.367, P < 0.001) and haemoglobulin levels (r = 0.193, P = 0.003). Patients with LN class III, subclass IV-S and those with thrombotic microangiopathy had the lowest serum CFH. CONCLUSION Serum CFH levels were associated with disease activity of LN.

Objective. Evidence shows that defensins are involved in the pathogenesis of SLE and ANCA-associated small vasculitis (AASV). The copy number variation of DEFB4 has been proposed to be susceptible to inflammatory disorders. This study aims to investigate whether the DEFB4 genomic copy number variations associate with the susceptibility to these two autoimmune diseases. Methods. A total of 1178 Chinese people were enrolled, including Panel 1 comprising 240 SLE patients and 275 matched controls, Panel 2 comprising 303 SLE patients and 248 matched controls and Panel 3 with 112 AASV patients. The DEFB4 copy number was typed by a paralogue ratio test (PRT), and all the subjects in Panel 1 were also typed using the restriction enzyme digest variant ratio (REDVR) for validation. Results. The results from PRT and REDVR were highly concordant (R = 0.911, P = 3.85 � 10 � 199 ) and allowed copy numbers to be assigned into integer classes with high confidence. Comparison of mean DEFB4 copy number revealed a small increase in cases with SLE both in Panel 1 (P = 0.063) and Panel 2 (P = 0.017). When pooling Panels 1 and 2 together, the association was reinforced (P = 0.002) in SLE. Such association was also observed in AASV (P = 0.009). Conclusion. We found that a higher DEFB4 gene copy number was associated with both SLE and AASV.

Objectives ANCAs with specificity for MPO are serological markers of ANCA-associated vasculitides, especially microscopic polyangiitis (MPA). This study investigated potential associations between the influence of MPO-ANCA on the oxidation activity of MPO and the clinical manifestations as well as immunological characteristics of MPO-ANCA. Methods MPO-ANCA was purified with MPO-affinity chromatography from plasma of 13 consecutive patients with MPO-ANCA-positive MPA. The titre, avidity, immunoglobulin G (IgG) subclasses and the ability to reverse the binding between ceruloplasmin and MPO of MPO-ANCA were tested using ELISA. The oxidation activity of MPO in the presence of MPO-ANCA was measured. The associations between the oxidation activity of MPO after binding MPO-ANCA and the clinical and immunological characteristics of MPO-ANCA were analysed. Results The MPO activity without binding to its autoantibodies was 1.521 (0.12) (expressed by A-values at 10 min, using o-phenylenediamine as substrate). After binding affinity-purified MPO-ANCA, the MPO activity ranged from 1.083 to 1.642. Correlation analysis showed that the oxidation activity of MPO after binding MPO-ANCA positively correlated with the level of ceruloplasmin binding on MPO in presence of MPO-ANCA (r = 0.617, P = 0.025) and negatively correlated with initial sera creatinine levels (r = -0.564, P = 0.045), BVAS (r = -0.735, P = 0.004), avidity of MPO-ANCA (r = -0.575, P = 0.040), levels of IgG2 (r = -0.610, P = 0.027) and IgG3 subclasses (r = -0.695, P = 0.008) of MPO-ANCA. Conclusions MPO-ANCA from different patients can influence MPO activity with different levels. The low oxidation activity of MPO after binding MPO-ANCA might be associated with more severe disease.