SummaryBackground and objectives B cell significance in ANCA disease pathogenesis is underscored by the finding that ANCA alone can cause disease in mouse models and by the effectiveness of rituximab as therapy in ANCA-small vessel vasculitis (ANCA-SVV). To avoid infections and adverse events from therapy, clinicians require improved markers of disease activity and impending relapse to guide immunosuppression strategies after rituximab treatment.Design, setting, participants, & measurements The B cell phenotype was investigated in patients with active ANCA-SVV and in remission. From 2003 to 2009, 54 patients were followed longitudinally for 4-99 months and compared with 68 healthy controls. In a subset of 19 patients, the B cell immunophenotype was examined in samples after rituximab therapy.Results Patients with active ANCA-SVV had lower %CD5 + B cells, whereas %CD5 + B cells from patients in remission were indistinguishable from healthy controls. After rituximab, median time to relapse was 31 months in patients maintaining normalized %CD5 + B cells, with or without maintenance immunosuppression. Among patients whose B cells repopulated with low %CD5 + B cells or had a sharply declining %CD5 + B cells, those who were on low or no maintenance immunosuppression relapsed sooner (median 17 months) than patients who were maintained on high levels of oral maintenance immunosuppression (29 months; P=0.002). Conclusions The %CD5+ B cells, as a component of the human B regulatory cell phenotype, is a useful indicator of disease activity, remission, and future relapse, and thus may guide remission maintenance therapy after rituximab treatment.

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Type 1 diabetes is an autoimmune disease mediated by β cell-specific CD4+ and CD8+ T cells. Tracking β cell-specific T cells is one approach to monitor the diabetogenic response in at risk or diabetic individuals. Such analyses, however, are limited to PBL because T cells infiltrating the pancreatic islets are normally inaccessible. A key issue is whether peripheral β cell-specific T cells accurately reflect those cells infiltrating the target tissue. We investigated the properties of CD4+ T cells specific for a mimetic epitope recognized by the BDC2.5 clonotypic TCR in NOD mice. Soluble IAg7-Ig (sIAg7-Ig) multimer complexes covalently linked to a mimetic BDC peptide (sIAg7-mBDC) were used to identify or isolate CD4+ T cells from PBL and the islets of NOD mice. A temporal increase in sIAg7-mBDC binding (g7-mBDC+) T cells corresponding with the progression of β cell autoimmunity was detected in both PBL and islets in NOD female mice. In contrast to T cells in PBL, however, the majority of islet g7-mBDC+ T cells exhibited a type 1 phenotype, and mediated diabetes upon transfer into NOD.scid recipients. TCR-β and CDR-β gene usage of single islet-infiltrating g7-mBDC+ CD4+ T cells from individual NOD mice showed a restricted repertoire dominated by one or two clones typically expressing TCR β-chain variable TRBV-15. In contrast, a distinct and diverse TCR repertoire was detected for PBL-derived g7-mBDC+ T cells. These results demonstrate that PBL and islet CD4+ T cells specific for a given β cell epitope can differ regarding pathogenicity and TCR repertoire.

Objective There is accumulating evidence that complement activation is important in antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV) pathogenesis. This study was undertaken to investigate complement activation in AAV with myeloperoxidase (MPO) positivity and AAV with proteinase 3 (PR3) positivity after determining optimal methods for measuring activated complement factors in circulation. Methods Participants included 98 patients with AAV (45 MPO‐ANCA positive, 53 PR3‐ANCA positive) and 35 healthy controls. Plasma was obtained from blood collected using EDTA tubes, with or without 100 μg/ml Futhan. Levels of Bb, C3a, C5a, soluble C5b–9 (sC5b–9), properdin, and C4d were measured by enzyme‐linked immunosorbent assay. Group comparisons were made using Wilcoxon's 2‐sample test. Paired data were analyzed using a matched pairs signed rank test. Results Compared to healthy controls, certain complement analyte levels were high in patients with active AAV with MPO positivity, including C3a (P < 0.0001), C5a (P = 0.0004), and sC5b–9 (P = 0.0007). During remission, levels of Bb (P = 0.001), C3a (P < 0.0001), and sC5b–9 (P = 0.003) were higher. Compared to healthy controls, C3a (P < 0.0001), C5a (P = 0.002), sC5b–9 (P = 0.0001), and C4d (P = 0.005) levels were higher in patients with active AAV with PR3 positivity; levels of C3a (P < 0.0001) and C4d (P = 0.007) were also higher duriing remission. There were no significant differences in any complement analyte for either ANCA serotype between patients with active disease and those with disease in remission. Among patients with paired samples, sC5‐9 levels were significantly lower during disease remission compared to active disease. C5a was significantly lower among patients with disease in long‐term remission who were not receiving therapy. For Bb, C5a, and sC5b–9, median levels and individual values were considerably higher in control and patient samples processed without Futhan compared to those processed with Futhan. Conclusion Complement activation occurs in both MPO‐positive AAV and PR3‐positive AAV. The complement activation profile differs according to disease activity and possibly ANCA serotype. Futhan reduces in vitro complement activation and provides a more accurate measurement.