Objective. B cell depletion with rituximab has allowed remissions in relapsing or refractory antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis in small studies. The aim of this study was to determine the efficacy and safety of rituximab for ANCA-associated vasculitis in a larger multicenter cohort. This permitted comparison of rituximab dosing regimens, the value of continuing immunosuppression, and investigation of ANCA and B cell levels as retreatment biomarkers.Methods. Retrospective, standardized data collection from 65 sequential patients receiving rituximab for refractory ANCA-associated vasculitis at 4 centers in the UK was used.Results. All patients achieved B cell depletion. Complete remission occurred in 49 of the 65 patients (75%), partial remission in 15 (23%), and no response in 1 (2%). The prednisolone dosage was reduced from 12.5 mg/day (median) to 9.0 mg/day at 6 months (P ‫؍‬ 0.0006). Immunosuppressive therapy was withdrawn in 37 of 60 patients (62%). Twenty-eight of 49 patients who achieved full remission (57%) experienced relapse (median 11.5 months). B cell return preceded relapse in 14 of 27 patients (52%). Although ANCA levels fell after rituximab therapy, relapse was not associated with ANCA positivity or a rise in ANCA levels. Neither the initial rituximab regimen (4 infusions of 375 mg/m 2 each given 1 week apart or 2 infusions of 1 gm each given 2 weeks apart) nor withdrawal of immunosuppressive therapy (37 of 60 patients [62%]) influenced the timing of relapse. Thirty-eight patients received >2 courses of rituximab, and complete remission was induced or maintained in 32 of them (84%). IgM levels fell, although IgG levels remained stable. Forty-six serious adverse events occurred, including 2 episodes of lateonset neutropenia, which were attributed to rituximab.Conclusion. Rituximab was effective remission induction therapy for refractory ANCA-associated vasculitis in this study. There was no difference in efficacy between the 2 main treatment regimens. Continuing immunosuppression did not reduce relapses. Relapses occurred, but re-treatment was effective and safe. There was no clear influence of rituximab on the frequency of serious adverse events. ANCA and B cell levels lacked sufficient sensitivity to guide the timing of re-treatment.

The induction of human CD4+ Th1 cells requires autocrine stimulation of the complement receptor CD46 in direct crosstalk with a CD4+ T cell-intrinsic NLRP3 inflammasome. However, it is unclear whether human cytotoxic CD8+ T cell (CTL) responses also rely on an intrinsic complement-inflammasome axis. Here we show, using CTLs from patients with CD46 deficiency or with constitutively-active NLRP3, that CD46 delivers co-stimulatory signals for optimal CTL activity by augmenting nutrient-influx and fatty acid synthesis. Surprisingly, although CTLs express NLRP3, a canonical NLRP3 inflammasome is not required for normal human CTL activity, as CTLs from patients with hyperactive NLRP3 activity function normally. These findings establish autocrine complement and CD46 activity as integral components of normal human CTL biology, and, since CD46 is only present in humans, emphasize the divergent roles of innate immune sensors between mice and men.

Many autoantibodies have variable-region sequences indicating their production in an affinity-matured antibody response involving germinal centers (GC). Plasma cells from GC can be long-lived, do not express CD20 and thus should not be depleted by a therapeutic monoclonal Ab against human CD20 -Rituximab. Nevertheless, autoantibody titers often fall following Rituximab treatment. To test if this reflects exclusive production by short-lived plasma cells in extrafollicular Ab responses, we monitored, after Rituximab treatment, levels of natural Ab and Ab against extrinsic antigens that do not induce productive GC. Eleven patients with active vasculitis and anti-proteinase-3 (PR3) Ab were assessed before and during 5 months after Rituximab therapy. Blood B cells were undetectable within 2 wk, and all patients achieved clinical remission. Levels of natural Ab -isohemagglutinins and anti-phosphorylcholine Ab -and Ab levels against thymus-independent and thymus-dependent extrinsic antigens were little affected. By contrast, 5 months after Rituximab, IgG autoantibody against PR3 had fallen to a median of 22% of pretreatment values. While the kinetics of this fall do not suggest an intrinsically short lifespan of autoantibody-producing cells, the data are consistent with Rituximab causing loss of sites within inflammatory tissues that selectively sustain autoantibody-producing cells.Supporting Information for this article is available at http://www.wiley-vch.de/contents/jc_2040/2007/37557_s.pdf IntroductionRituximab is an IgG1 chimeric mouse/human monoclonal Ab directed against human CD20 that was developed for the treatment of lymphoma. Its administration causes profound depletion of B cells, which express CD20, from blood and tissues [1]. Rituximab has been used successfully to treat a number of autoimmune diseases. Significant falls in disease-associated IgG and IgM autoantibody levels are often seen [2-5] although this does not always happen [6, 7].Autoantibodies against the neutrophil serine protease, proteinase-3 (PR3), are encoded by Ig V region genes that have acquired somatic mutations [8]. These findings are consistent with the autoantibodies being produced by plasma cells whose precursors have undergone affinity maturation through hypermutation of their Ig V region genes and selection in germinal centers (GC) [9], although Ig V region mutations can be Certain types of Ag seem to induce only extrafollicular Ab responses, and many of the Ab-forming cells produced in these responses are short-lived [16,17]. These Ag include those based on pure polysaccharides and lipopolysaccharides that are not able to complete the CD4 T cell-dependent selection process required for plasma cells to differentiate from GC B cells [9]. In addition, B1 cells produce extrafollicular Ab responses, but probably do not form GC [18].B cell depletion by Rituximab provides the opportunity to investigate whether cells that maintain chronic Ab production after an extrafollicular response to Ag can be long-lived in the absence of B cell prec...

IntroductionHomeostatic chemokines, including CXCL13, CXCL19/CXCL21, and CXCL12, are essential organizers of lymphoid tissues in steady states. For instance, they govern the compartmentalization between T and B cells. Importantly, they are also involved in the repositioning of these lymphocytes during the different stages of immune responses. The development of protective memory B cells and long-lived AFCs relies in part on changing expression by the responding B cells of the receptors for the chemokines CXCR5, CCR7, and CXCR4, and of the orphan receptor Epstein-Barr virus-induced molecule-2. 1-3 Thus, during the development of T-dependent antibody responses to protein-based antigens, such as alum-precipitated protein vaccines, chemokine-driven movements in lymph nodes (LNs) are sequentially involved in: (1) the cognate interaction of activated B cells with primed CD4 T cells [4][5][6] in the outer T zone, resulting in B-cell proliferation and class-switch recombination (CSR); or (2) the signals that determine whether B blasts differentiate outside follicles into AFCs without going through affinity maturation 1,3 or form germinal center (GC) in follicles. 2 Through CXCR4-and CXCR5-dependent movements, B cells undergo affinity maturation in GC through proliferation, hypermutation of their immunoglobulin (Ig) variable region genes, and selection of high-affinity mutants that emerge as memory B cells or long-lived AFCs. 7,8 The acquisition of CXCR4 by AFC attracts them to CXCL12 produced in bone marrow's long-term survival niches. In these niches, they maintain protective antibody titers over months. 9,10 Alongside the varying expression of CXCR5/CCR7/CXCR4 that modulates B-cell chemotaxis toward homeostatic chemokines, inflammatory conditions can induce IFN-␥-dependent expression of CXCR3 by lymphocytes, including AFCs. This receptor confers responsiveness to CXCL9, CXCL10, and CXCL11, which are produced at high levels in sites of inflammation. 11 This CXCR3-dependent pathway is important for the recruitment of lymphocytes at sites of infection and clearance of pathogens. 12,13 For instance, CXCR3 expression by mouse AFCs is critical for their migration to the CNS during viral encephalomyelitis. Thus, CXCR3-dependent migration of AFCs to the site of infection clears the virus from the CNS, although this is not achieved with systemic release of antibody. 14,15 CXCR3 ϩ AFCs and memory B cells were found at particularly high frequency in peripheral blood of patients with autoimmune diseases mediated by autoantibodies. 16,17 This suggests that selfreactive AFCs may be produced and/or attracted to and sustained in chronic inflammatory niches through a mechanism that involves CXCR3 and its ligands. 18 In mouse models for lupus erythematosus, AFCs are found in inflamed tissues. 19 Knockdown of CXCR3 has shown the importance of this chemokine receptor in the development of the autoimmune disorders, 20 including the production anti-double-stranded DNA IgG1. 21 Despite the importance of CXCR3 induction for antibody producti...