Extrarenal symptoms associate with worse quality of life in patients enrolled in the AMP RA/SLE Lupus Nephritis Network

OBJECTIVE

Lupus nephritis (LN) can occur as an isolated component of disease activity or be accompanied by diverse extrarenal manifestations. Whether isolated renal disease is sufficient to decrease health related quality of life (HRQOL) remains unknown. This study compared Patient-Reported Outcomes Measurement Information System 29-Item (PROMIS-29) scores in LN patients with isolated renal disease to those with extrarenal symptoms to evaluate the burden of LN on HRQOL and inform future LN clinical trials incorporating HRQOL outcomes.

METHODS

A total of 181 LN patients consecutively enrolled in the multicentre multi-ethnic/racial Accelerating Medicines Partnership completed PROMIS-29 questionnaires at the time of a clinically indicated renal biopsy. Raw PROMIS-29 scores were converted to standardized T scores.

RESULTS

Seventy-five (41%) patients had extrarenal disease (mean age 34, 85% female) and 106 (59%) had isolated renal (mean age 36, 82% female). Rash (45%), arthritis (40%) and alopecia (40%) were the most common extrarenal manifestations. Compared with isolated renal, patients with extrarenal disease reported significantly worse pain interference, ability to participate in social roles, physical function, and fatigue. Patients with extrarenal disease had PROMIS-29 scores that significantly differed from the general population by > 0.5 SD of the reference mean in pain interference, physical function, and fatigue. Arthritis was most strongly associated with worse scores in these three domains.

CONCLUSION

Most patients had isolated renal disease and extrarenal manifestations associated with worse HRQOL. These data highlight the importance of comprehensive disease management strategies that address both renal and extrarenal manifestations to improve overall patient outcomes.

Associations Between Rheumatoid Arthritis Clinical Factors and Synovial Cell Types and States

OBJECTIVE

Recent studies have uncovered diverse cell types and states in the rheumatoid arthritis (RA) synovium; however, limited data exist correlating these findings with patient-level clinical information. Using the largest cohort to date with clinical and multicell data, we determined associations between RA clinical factors with cell types and states in the RA synovium.

METHODS

The Accelerated Medicines Partnership Rheumatoid Arthritis study recruited patients with active RA who were not receiving disease-modifying antirheumatic drugs (DMARDs) or who had an inadequate response to methotrexate (MTX) or tumor necrosis factor inhibitors. RA clinical factors were systematically collected. Biopsies were performed on an inflamed joint, and tissue were disaggregated and processed with a cellular indexing of transcriptomes and epitopes sequencing pipeline from which the following cell type percentages and cell type abundance phenotypes (CTAPs) were derived: endothelial, fibroblast, and myeloid (EFM); fibroblasts; myeloid; T and B cells; T cells and fibroblasts (TF); and T and myeloid cells. Correlations were measured between RA clinical factors, cell type percentage, and CTAPs.

RESULTS

We studied 72 patients (mean age 57 years, 75% women, 83% seropositive, mean RA duration 6.6 years, mean Disease Activity Score-28 C-reactive Protein 3 [DAS28-CRP3] score 4.8). Higher DAS28-CRP3 correlated with a higher T cell percentage (P < 0.01). Those receiving MTX and not a biologic DMARD (bDMARD) had a higher percentage of B cells versus those receiving no DMARDs (P < 0.01). Most of those receiving bDMARDs were categorized as EFM (57%), whereas none were TF. No significant difference was observed across CTAPs for age, sex, RA disease duration, or DAS28-CRP3.

CONCLUSION

In this comprehensive screen of clinical factors, we observed differential associations between DMARDs and cell phenotypes, suggesting that RA therapies, more than other clinical factors, may impact cell type/state in the synovium and ultimately influence response to subsequent therapies.

Longitudinal patterns and predictors of response to standard-of-care therapy in lupus nephritis: data from the Accelerating Medicines Partnership Lupus Network

BACKGROUND

Leveraging the Accelerating Medicines Partnership (AMP) Lupus Nephritis (LN) dataset, we evaluated longitudinal patterns, rates, and predictors of response to standard-of-care therapy in patients with lupus nephritis.

METHODS

Patients from US academic medical centers with class III, IV, and/or V LN and a baseline urine protein/creatinine (UPCR) ratio ≥ 1.0 (n = 180) were eligible for this analysis. Complete response (CR) required the following: (1) UPCR < 0.5; (2) normal serum creatinine (≤ 1.3 mg/dL) or, if abnormal, ≤ 125% of baseline; and (3) prednisone ≤ 10 mg/day. Partial response (PR) required the following: (1) > 50% reduction in UPCR; (2) normal serum creatinine or, if abnormal, ≤ 125% of baseline; and (3) prednisone dose ≤ 15 mg/day.

RESULTS

Response rates to the standard of care at week 52 were CR = 22.2%; PR = 21.7%; non-responder (NR) = 41.7%, and not determined (ND) = 14.4%. Only 8/180 (4.4%) patients had a week 12 CR sustained through week 52. Eighteen (10%) patients attained a week 12 PR or CR and sustained their responses through week 52 and 47 (26.1%) patients achieved sustained PR or CR at weeks 26 and 52. Week 52 CR or PR attainment was associated with baseline UPCR > 3 (ORadj = 3.71 [95%CI = 1.34-10.24]; p = 0.012), > 25% decrease in UPCR from baseline to week 12 (ORadj = 2.61 [95%CI = 1.07-6.41]; p = 0.036), lower chronicity index (ORadj = 1.33 per unit decrease [95%CI = 1.10-1.62]; p = 0.003), and positive anti-dsDNA antibody (ORadj = 2.61 [95%CI = 0.93-7.33]; p = 0.069).

CONCLUSIONS

CR and PR rates at week 52 were consistent with the standard-of-care response rates observed in prospective registrational LN trials. Low sustained response rates underscore the need for more efficacious therapies and highlight how critically important it is to understand the molecular pathways associated with response and non-response.

High incidence of proliferative and membranous nephritis in SLE patients with low proteinuria in the Accelerating Medicines Partnership

OBJECTIVE

Delayed detection of LN associates with worse outcomes. There are conflicting recommendations regarding a threshold level of proteinuria at which biopsy will likely yield actionable management. This study addressed the association of urine protein:creatinine ratios (UPCR) with clinical characteristics and investigated the incidence of proliferative and membranous histology in patients with a UPCR between 0.5 and 1.

METHODS

A total of 275 SLE patients (113 first biopsy, 162 repeat) were enrolled in the multicentre multi-ethnic/racial Accelerating Medicines Partnership across 15 US sites at the time of a clinically indicated renal biopsy. Patients were followed for 1 year.

RESULTS

At biopsy, 54 patients had UPCR <1 and 221 had UPCR ≥1. Independent of UPCR or biopsy number, a majority (92%) of patients had class III, IV, V or mixed histology. Moreover, patients with UPCR <1 and class III, IV, V, or mixed had a median activity index of 4.5 and chronicity index of 3, yet 39% of these patients had an inactive sediment. Neither anti-dsDNA nor low complement distinguished class I or II from III, IV, V or mixed in patients with UPCR <1. Of 29 patients with baseline UPCR <1 and class III, IV, V or mixed, 23 (79%) had a UPCR <0.5 at 1 year.

CONCLUSION

In this prospective study, three-quarters of patients with UPCR <1 had histology showing class III, IV, V or mixed with accompanying activity and chronicity despite an inactive sediment or normal serologies. These data support renal biopsy at thresholds lower than a UPCR of 1.

Safety of procuring research tissue during a clinically indicated kidney biopsy from patients with lupus: data from the Accelerating Medicines Partnership RA/SLE Network

Objectives

In lupus nephritis the pathological diagnosis from tissue retrieved during kidney biopsy drives treatment and management. Despite recent approval of new drugs, complete remission rates remain well under aspirational levels, necessitating identification of new therapeutic targets by greater dissection of the pathways to tissue inflammation and injury. This study assessed the safety of kidney biopsies in patients with SLE enrolled in the Accelerating Medicines Partnership, a consortium formed to molecularly deconstruct nephritis.

Methods

475 patients with SLE across 15 clinical sites in the USA consented to obtain tissue for research purposes during a clinically indicated kidney biopsy. Adverse events (AEs) were documented for 30 days following the procedure and were determined to be related or unrelated by all site investigators. Serious AEs were defined according to the National Institutes of Health reporting guidelines.

Results

34 patients (7.2%) experienced a procedure-related AE: 30 with haematoma, 2 with jets, 1 with pain and 1 with an arteriovenous fistula. Eighteen (3.8%) experienced a serious AE requiring hospitalisation; four patients (0.8%) required a blood transfusion related to the kidney biopsy. At one site where the number of cores retrieved during the biopsy was recorded, the mean was 3.4 for those who experienced a related AE (n=9) and 3.07 for those who did not experience any AE (n=140). All related AEs resolved.

Conclusions

Procurement of research tissue should be considered feasible, accompanied by a complication risk likely no greater than that incurred for standard clinical purposes. In the quest for targeted treatments personalised based on molecular findings, enhanced diagnostics beyond histology will likely be required.

IFN signaling inhibits osteogenesis in human SLE bone marrow

BACKGROUND

Bone marrow mesenchymal stem cells are multipotent adult stem cells that can differentiate into osteoblasts, adipocytes, and chondrocytes. Our recently published data demonstrate that systemic lupus erythematous bone marrow mesenchymal stem cells produce increased quantities of interferon β based on a positive feedback loop involving the innate signaling molecule mitochondrial antiviral signaling protein. Moreover, this pathway contributes to human systemic lupus erythematous bone marrow mesenchymal stem cell senescence-like features. Here we investigate the differentiation defects of systemic lupus erythematous bone marrow mesenchymal stem cells and the potential for therapeutic interventions.

METHODS

The six systemic lupus erythematous patients recruited in this study satisfy the American College of Rheumatology 1997 classification criteria for systemic lupus erythematous. Systemic Lupus Erythematous Disease Activity Index-2K was used to determine disease activity. Systemic lupus erythematous bone marrow mesenchymal stem cells were isolated with Ficoll centrifugation and phenotyped using flow cytometry. In vitro studies included real-time polymerase chain reaction and western blotting.

RESULTS

We compared six age-paired bone marrow aspirates from healthy controls and systemic lupus erythematous patients. Systemic lupus erythematous bone marrow mesenchymal stem cells display significantly reduced alkaline phosphatase staining, as well as reduced expression of osteogenic markers alkaline phosphatase, Runt-related transcription factor 2, and bone sialoprotein. When healthy bone marrow mesenchymal stem cells were treated with interferon β for 6 hours, expression of these same osteogenic markers was markedly reduced. Conversely the application of interferon β neutralizing antibody enhanced the expression of osteoblastogenesis markers. When the underlying mechanisms for interferon β inhibition of osteoblastogenesis were investigated, we found that IFNβ pre-treatment activates the inhibitory Smad6 and Smad7 expression through JAK1/STAT1, leading to reduced Smad1 phosphorylation and nuclear translocation.

CONCLUSIONS

Our present work suggests that interferon β affects osteogenesis. By revealing the essential role of interferon β on systemic lupus erythematous bone marrow mesenchymal stem cell differentiation, our study sheds light on systemic lupus erythematous pathogenesis and provides a new potential therapeutic target for the bone complications found in systemic lupus erythematous.

Correction to: Cell Senescence in Lupus

The original version of this article unfortunately contained mistakes.

Cell Senescence in Lupus

Purpose of Review

The concept of cellular senescence has been evolving. Although originally proposed based on studies of serum-driven replication of cell lines in vitro, it is now clear that cellular senescence occurs in vivo. It has also become clear that cellular senescence can be triggered by a number of stimuli such as radiation, chemotherapy, activation of oncogenes, metabolic derangements, and chronic inflammation.

Recent Findings

As we learn more about the mechanisms of cellular aging, it has become important to ask whether accelerated cellular senescence occurs in lupus and other systemic rheumatologic diseases.

Summary

Accelerated cellular aging may be one explanation for some of the excess morbidity and mortality seen in lupus patients. If so, drugs targeting cellular senescence may provide new options for preventing long-term complications such as organ failure in systemic lupus erythematosus patients.

Bone Marrow-Derived Mesenchymal Stem Cells From Patients With Systemic Lupus Erythematosus Have a Senescence-Associated Secretory Phenotype Mediated by a Mitochondrial Antiviral Signaling Protein-Interferon-β Feedback Loop

OBJECTIVE

Bone marrow-derived mesenchymal stem cells (BM-MSCs) create a special microenvironment for hematopoiesis and immunity and display robust immunomodulatory properties that are impaired in systemic lupus erythematosus (SLE). This study was undertaken to identify the mechanisms of defects in human SLE BM-MSCs.

METHODS

Patients fulfilling SLE classification criteria and healthy controls (n = 6 per group) were recruited according to an institutional review board-approved protocol. BM-MSCs were isolated with low-density Ficoll-Hypaque, verified by flow cytometry, and studied using immunocytochemistry, real-time polymerase chain reaction, Western blotting, comet assay, β-galactosidase assay, and RNA interference.

RESULTS

SLE BM-MSCs had a senescent phenotype characterized by a reduced proliferation rate, increased production of reactive oxygen species, increased DNA damage and repair, increased expression of p53 and p16, which block the cell cycle, and altered cytokine production (increased proinflammatory cytokine production and decreased immunomodulatory cytokine production). Moreover, SLE BM-MSCs had a 5-fold increase in interferon-β (IFNβ) levels (P < 0.05 versus healthy controls) and increased IFNβ-induced messenger RNAs (mRNAs), including mRNA for the intracellular nucleic acid-sensing adaptor protein mitochondrial antiviral signaling protein (MAVS), whose expression was highly correlated with IFNβ levels (r > 0.9, P < 0.01). Since MAVS is known to induce IFNβ production, we hypothesized that there is a positive feedback loop between MAVS and IFNβ. Notably, silencing of MAVS markedly decreased IFNβ, p53, and p16 protein levels and expression of mRNAs for proinflammatory cytokines.

CONCLUSION

This study demonstrates a novel pathway for elevated IFNβ signaling in SLE that is not dependent on stimulation by immune complexes but rather is cell intrinsic and critically mediated by IFNβ and MAVS, implicating new pathways as potential therapeutic targets.

PKK deficiency in B cells prevents lupus development in Sle lupus mice

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of autoantibodies that can result in damage to multiple organs. It is well documented that B cells play a critical role in the development of the disease. We previously showed that protein kinase C associated kinase (PKK) is required for B1 cell development as well as for the survival of recirculating mature B cells and B-lymphoma cells. Here, we investigated the role of PKK in lupus development in a lupus mouse model. We demonstrate that the conditional deletion of PKK in B cells prevents lupus development in Sle1Sle3 mice. The loss of PKK in Sle mice resulted in the amelioration of multiple classical lupus-associated phenotypes and histologic features of lupus nephritis, including marked reduction in the levels of serum autoantibodies, proteinuria, spleen size, peritoneal B-1 cell population and the number of activated CD4 T cells. In addition, the abundance of autoreactive plasma cells normally seen in Sle lupus mice was also significantly decreased in the PKK-deficient Sle mice. Sle B cells deficient in PKK display defective proliferation responses to BCR and LPS stimulation. Consistently, B cell receptor-mediated NF-κB activation, which is required for the survival of activated B cells, was impaired in the PKK-deficient B cells. Taken together, our work uncovers a critical role of PKK in lupus development and suggests that targeting the PKK-mediated pathway may represent a promising therapeutic strategy for lupus treatment.

B lymphocytes in systemic lupus erythematosus: lessons from therapy targeting B cells

Systemic lupus erythematosus (SLE) is a complex disease characterizedby numerous autoantibodies and clinical involvement in multiple organ systems. Autoantibodies are usually present in serum for years before the onset of clinical disease. Autoimmunity begins with a limited number of autoantibodiesand evolves to become progressivelymore diverse. Eventually clinical disease ensues. The immunological events triggering the onset of clinical manifestations have not yet been defined. While undoubtedly T cells and dendritic cells appear to play major roles in SLE, a central role for B cells in the pathogenesis of this disease has been brought to the fore in the last few years by work performed both in mice and humans by multiple laboratories.As a result, there is little doubt about the importance of B cells in the development of SLE. Yet much remains to be learned about their role in the ongoing disease process and the merit of targeting B cells for the treatment of SLE. This article will review the role of B cells in human SLE as well as the currently available data on the treatment of SLE by depleting B cells with anti-CD20 (rituximab).

Antibody-Array-Based Proteomic Screening of Serum Markers in Systemic Lupus Erythematosus: A Discovery Study

A discovery study was carried out where serum samples from 22 systemic lupus erythematosus (SLE) patients and matched healthy controls were hybridized to antibody-coated glass slide arrays that interrogated the level of 274 human proteins. On the basis of these screens, 48 proteins were selected for ELISA-based validation in an independent cohort of 28 SLE patients. Whereas AXL, ferritin, and sTNFRII were significantly elevated in patients with active lupus nephritis (LN) relative to SLE patients who were quiescent, other molecules such as OPN, sTNFRI, sTNFRII, IGFBP2, SIGLEC5, FAS, and MMP10 exhibited the capacity to distinguish SLE from healthy controls with ROC AUC exceeding 90%, all with p < 0.001 significance. These serum markers were next tested in a cohort of 45 LN patients, where serum was obtained at the time of renal biopsy. In these patients, sTNFRII exhibited the strongest correlation with eGFR (r = -0.50, p = 0.0014) and serum creatinine (r = 0.57, p = 0.0001), although AXL, FAS, and IGFBP2 also correlated with these clinical measures of renal function. When concurrent renal biopsies from these patients were examined, serum FAS, IGFBP2, and TNFRII showed significant positive correlations with renal pathology activity index, while sTNFRII displayed the highest correlation with concurrently scored renal pathology chronicity index (r = 0.57, p = 0.001). Finally, in a longitudinal cohort of seven SLE patients examined at ∼3 month intervals, AXL, ICAM-1, IGFBP2, SIGLEC5, sTNFRII, and VCAM-1 demonstrated the ability to track with concurrent disease flare, with significant subject to subject variation. In summary, serum proteins have the capacity to identify patients with active nephritis, flares, and renal pathology activity or chronicity changes, although larger longitudinal cohort studies are warranted.

Neutrophils modulate the progression of B cell auto-reactivity in systemic lupus erythematosus

The central feature of systemic lupus erythematosus (SLE) pathogenesis is loss of immunologic self-tolerance. Here, we address a current controversy regarding whether neutrophils influence the development of B cell auto-reactivity SLE. While both human and murine lupus neutrophils produce factors known to fuel adaptive immune dysregulation, including type I interferon, B cell survival factors, and extracellular traps (a putative source of self-antigen), some studies have contended that neutrophils in peripheral lymphoid organs (PLO) suppress B cell activation and differentiation. In order to ask whether neutrophils exert regulatory or deleterious effects on loss of B cell self-tolerance and immune activation, we compare changes in SLE progression following neutrophil depletion in the NZB/W lupus model, either during or after establishment of disease. Following depletion early in disease, we observe pronounced acceleration of proteinuria, anti-dsDNA titers, and germinal center formation. However, neutrophil depletion after onset of overt disease pathology (including proteinuria) does not strongly alter SLE progression, implicating neutrophils as playing a protective role only apparent during disease onset. To elucidate the specific mechanisms underlying neutrophil effects on B cell auto-reactivity, we examine the cytokine profile of neutrophils in direct proximity to B cells in PLO during several stages of disease. With progression of disease, we observe an influx of interferon-alpha-producing neutrophils in direct proximity to B cells in PLO. These data delineate a shifting balance of both regulatory and activating roles for neutrophils in auto-reactive B cell activation/proliferation during SLE progression.

The role of neutrophils in B cell dysregulation in systemic lupus erythematosus (BA7P.146)

Systemic lupus erythematosus (SLE) is an autoimmune disease involving dysregulation of both innate and adaptive immune compartments. The hallmark of SLE is loss of B cell tolerance and production of auto-antibodies, which results in tissue damage and inflammation. Factors driving loss of B cell tolerance are incompletely characterized, but include failure of central tolerance mechanisms, inadequate clearance of cell debris, and alterations in the cytokine milieu, including elevated interferon alpha (IFNα). Our lab and others have shown that SLE neutrophils are a significant source of IFNα as well as self-antigen in the form of apoptotic debris and neutrophil extracellular traps (NETs). However, it is unknown whether neutrophils contribute to B cell activation and tolerance loss in lupus. To address this, we examined both splenic and bone marrow (BM) tissues from lupus prone mice to determine whether neutrophils secrete cytokines that alter the inflammatory milieu. Our data shows that neutrophil numbers and apoptosis are increased in lupus BM. BM neutrophils from lupus prone mice have elevated production of the B cell survival cytokines BAFF and APRIL, as well as IFNα. There was an enrichment of IFNα-producing neutrophils in the spleen in close proximity to both B and T cells. These data suggests that neutrophils likely participate in the creation of an inflammatory microenvironment that sustains auto-reactive B cells and exacerbates SLE pathogenesis in the spleen and the BM.

Primary Sjögren's syndrome is characterized by distinct phenotypic and transcriptional profiles of IgD+ unswitched memory B cells

OBJECTIVE

The significance of distinct B cell abnormalities in primary Sjögren's syndrome (SS) remains to be established. We undertook this study to analyze the phenotype and messenger RNA (mRNA) transcript profiles of B cell subsets in patients with primary SS and to compare them with those in sicca syndrome patients and healthy controls.

METHODS

CD19+ B cells from 26 patients with primary SS, 27 sicca syndrome patients, and 22 healthy controls were analyzed by flow cytometry. Gene expression profiles of purified B cell subsets (from 3-5 subjects per group per test) were analyzed using Affymetrix gene arrays.

RESULTS

Patients with primary SS had lower frequencies of CD27+IgD- switched memory B cells and CD27+IgD+ unswitched memory B cells compared with healthy controls. Unswitched memory B cell frequencies were also lower in sicca syndrome patients and correlated inversely with serologic hyperactivity in both disease states. Further, unswitched memory B cells in primary SS had lower expression of CD1c and CD21. Gene expression analysis of CD27+ memory B cells separated patients with primary SS from healthy controls and identified a subgroup of sicca syndrome patients with a primary SS-like transcript profile. Moreover, unswitched memory B cell gene expression analysis identified 187 genes differentially expressed between patients with primary SS and healthy controls.

CONCLUSION

A decrease in unswitched memory B cells with serologic hyperactivity is characteristic of both established primary SS and a subgroup of sicca syndrome, which suggests the value of these B cells both as biomarkers of future disease progression and for understanding disease pathogenesis. Overall, the mRNA transcript analysis of unswitched memory B cells suggests that their activation in primary SS takes place through innate immune pathways in the context of attenuated antigen-mediated adaptive signaling. Thus, our findings provide important insight into the mechanisms and potential consequences of decreased unswitched memory B cells in primary SS.

A perspective on B-cell-targeting therapy for SLE

In recent years, large controlled trials have tested several new agents for systemic lupus erythematosus (SLE). Unfortunately, none of these trials has met its primary outcome. This does not mean progress has not been made. In fact, a great deal has been learned about doing clinical trials in lupus and about the biological and clinical effects of the drugs being tested. Many of these drugs were designed to target B cells directly, e.g., rituximab, belimumab, epratuzumab, and transmembrane activator and calcium modulator and cyclophilin ligand interactor-immunoglobulin (TACI-Ig). The enthusiasm for targeting B cells derives from substantial evidence showing the critical role of B cells in murine models of SLE, as well promising results from multiple open trials with rituximab, a chimeric anti-CD20 monoclonal antibody that specifically depletes B cells (Martin and Chan in Immunity 20(5):517-527, 2004; Sobel et al. in J Exp Med 173:1441-1449, 1991; Silverman and Weisman in Arthritis Rheum 48:1484-1492, 2003; Silverman in Arthritis Rheum 52(4):1342, 2005; Shlomchik et al. in Nat Rev Immunol 1:147-153, 2001; Looney et al. in Arthritis Rheum 50:2580-2589, 2004; Lu et al. in Arthritis Rheum 61(4):482-487, 2009; Saito et al. in Lupus 12(10):798-800, 2003; van Vollenhoven et al. in Scand J Rheumatol 33(6):423-427, 2004; Sfikakis et al. Arthritis Rheum 52(2):501-513, 2005). Why have the controlled trials of B-cell-targeting therapies failed to demonstrate efficacy? Were there flaws in design or execution of these trials? Or, were promising animal studies and open trials misleading, as so often happens? This perspective discusses the current state of B-cell-targeting therapies for human lupus and the future development of these therapies.

Phenotypic and functional heterogeneity of human memory B cells

Memory B cells are more heterogeneous than previously thought. Given that B cells play powerful antibody-independent effector functions, it seems reasonable to assume division of labor between distinct memory B cells subpopulations in both protective and pathogenic immune responses. Here we review the information emerging regarding the heterogeneity of human memory B cells. A better understanding of this topic should greatly improve our ability to target specific B cell subsets either in vaccine responses or in autoimmune diseases and organ rejection among other pathological conditions where B cells play central pathogenic roles.

A novel subset of memory B cells is enriched in autoreactivity and correlates with adverse outcomes in SLE

We previously reported that some systemic lupus erythematosus (SLE) patients have a population of circulating memory B cells with >2-fold higher levels of CD19. We show here that the presence of CD19(hi) B cells correlates with long-term adverse outcomes. These B cells do not appear anergic, as they exhibit high basal levels of phosphorylated Syk and ERK1/2, signal transduce in response to BCR crosslinking, and can become plasma cells (PCs) in vitro. Autoreactive anti-Smith (Sm) B cells are enriched in this population and the degree of enrichment correlates with the log of the serum anti-Sm titer, arguing that they undergo clonal expansion before PC differentiation. PC differentiation may occur at sites of inflammation, as CD19(hi) B cells have elevated CXCR3 levels and chemotax in response to its ligand CXCL9. Thus, CD19(hi) B cells are precursors to anti-self PCs, and identify an SLE patient subset likely to experience poor clinical outcomes.

Vaccine responses in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease that is associated with immunologic alterations in T cells and B cells. Moreover, many of the agents used in RA patients are potentially immunosuppressive. Thus, the underlying disease and treatment may both increase the susceptibility to infections and decrease vaccine responses. With the growing use of aggressive therapies for RA, including anti-tumor necrosis factor agents and newer biologic therapies such as rituximab and abatacept, an increasing concern will be that patients may not respond to conventional vaccination. Further prospective studies on response to vaccination are needed to answer this important public health question. Nevertheless, it is already clear that vaccination does induce response in many patients. Unfortunately, vaccination is underutilized in RA patients and needs to be aggressively promoted.

A new population of cells lacking expression of CD27 represents a notable component of the B cell memory compartment in systemic lupus erythematosus

Human memory B cells comprise isotype-switched and nonswitched cells with both subsets displaying somatic hypermutation. In addition to somatic hypermutation, CD27 expression has also been considered a universal memory B cell marker. We describe a new population of memory B cells containing isotype-switched (IgG and IgA) and IgM-only cells and lacking expression of CD27 and IgD. These cells are present in peripheral blood and tonsils of healthy subjects and display a degree of hypermutation comparable to CD27+ nonswitched memory cells. As conventional memory cells, they proliferate in response to CpG DNA and fail to extrude rhodamine. In contrast to other recently described CD27-negative (CD27neg) memory B cells, they lack expression of FcRH4 and recirculate in the peripheral blood. Although CD27neg memory cells are relatively scarce in healthy subjects, they are substantially increased in systemic lupus erythematosus (SLE) patients in whom they frequently represent a large fraction of all memory B cells. Yet, their frequency is normal in patients with rheumatoid arthritis or chronic hepatitis C. In SLE, an increased frequency of CD27neg memory cells is significantly associated with higher disease activity index, a history of nephritis, and disease-specific autoantibodies (anti-dsDNA, anti-Smith (Sm), anti-ribonucleoprotein (RNP), and 9G4). These findings enhance our understanding of the B cell diversification pathways and provide mechanistic insight into the immunopathogenesis of SLE.

New therapies for systemic lupus erythematosus: cellular targets

Antilymphocyte antibodies have been widely used in oncology and transplantation and are now being tested in autoimmune diseases. For systemic lupus erythematosus, anti-B-cell antibodies are furthest along in development. This article discusses the B-cell abnormalities found in systemic lupus erythematosus and the clinical and immunologic effects of anti-B-cell therapies.

Reconstitution of the adult B cell repertoire after treatment with rituximab

B cells play diverse and fundamental roles in the pathogenesis of autoimmune diseases. Consequently, therapeutic targeting of B cells is gaining prominence in our clinical armamentarium for an ever expanding array of autoimmune and neoplastic disorders. Therefore, it is of great importance to understand the mechanism of action of B cell depletion. Given that the ideal consequence of B cell depletion would be the subsequent re-establishment of immunologic tolerance, a detailed analysis of the properties of the emerging repertoire will be required. The results presented by Rouzière and coworkers in their study of rheumatoid arthritis patients shed some light on this question and are discussed in this commentary.

Human innate B cells: a link between host defense and autoimmunity?

B cells play a variety of immunoregulatory roles through their antigen-presentation ability and through cytokine and chemokine production. Innate immune activation of B cells may play a beneficial role through the generation of natural cross-reactive antibodies, by maintaining B cell memory and by exercising immunomodulatory functions that may provide protection against autoimmunity. In this article, we review human B cell populations and their functional properties, with a particular focus on a population of inherently autoreactive B cells, which seem to play an important physiological role in innate immunity, but which, if selected into adaptive immune responses, appear to become pathogenic agents in systemic lupus erythematosus.

Treatment of SLE with anti-CD20 monoclonal antibody

Systemic lupus erythemaotsus (SLE) is an autoimmune disease involving multiple organ systems and characterized by anti-nuclear antibodies. While T cells and dendritic cells may play major roles in SLE, several lines of evidence strongly suggest a central role for B cells. This article will review the role of B cells in human SLE as well as the currently available data on the treatment of SLE by depleting B cells with anti-CD20 (rituximab).

B cells in human and murine systemic lupus erythematosus

PURPOSE OF REVIEW

The purpose of this review is to discuss recent publications dealing with the control of autoreactive B cells, how this control is subverted in human systemic lupus erythematosus and in murine models of systemic lupus erythematosus, and how dysregulated autoreactive B cells may then contribute to disease expression through both regulatory and effector mechanisms.

RECENT FINDINGS

Autoreactive B cells are abundant in the mature peripheral B-cell repertoire and need to be censored to avoid autoimmunity. This censoring is accomplished in diverse ways and may be broken down by multiple mechanisms both intrinsic and extrinsic to the B cells.

SUMMARY

The work reviewed here paints a suggestive picture while confirming the pathogenic potential of autoreactive B cells and pointing to specific defects that warrant further exploration and could represent future therapeutic targets for this autoimmune disease.

B cells as therapeutic targets for rheumatic diseases

PURPOSE OF REVIEW

Trials treating human rheumatic diseases with biologic agents and drugs that selectively affect B cells will be reviewed. Rituximab, an anti-CD20 monoclonal mouse/human antibody, will be the primary focus of the review because it has been widely used in several autoimmune and rheumatic conditions, but the limited studies on other reagents such as anti-BlyS, anti-CD154, and B cell tolerogens will also be covered.

RECENT FINDINGS

The single most important recent development was the completion of a randomized, double-blind, placebo-controlled trial of rituximab in methotrexate-resistant rheumatoid arthritis. In this trial, B cell depletion with rituximab led to a sustained clinical response with an impressive improvement in America College of Rheumatology 50% response (ACR 50) at both 24 and 48 weeks. Additional open studies of rituximab showing clinical benefit in systemic lupus erythematosus, cryoglobulinemia, antineutrophil cytoplasmic antibodies+ vasculitis, and dermatomyositis are noteworthy but must be interpreted with caution until randomized control trials are available. Two well-designed studies of anti-CD154 antibodies in systemic lupus erythematosus were reported. Unfortunately, one was halted because of unexpected vascular complications, and the other failed to show any beneficial clinical effect. A phase I study using anti-BlyS in SLE demonstrated a selective effect on B cells and no overt toxicity, but in this very short-term study no effect on serology or clinical activity was seen. Two B cell tolerogens have been used in human trials. The first tolerogen, directed at anti-dsDNA responses in SLE, did significantly decrease titers of high-affinity anti-dsDNA antibodies but had no clinically beneficial effect overall. A phase I trial of a tolerogen directed at anti-beta2-glycoprotein I antibodies demonstrated a decrease in antibody titers after a single injection.

SUMMARY

Several therapeutic agents targeting B cells have now been tested or are being tested in human trials. The success of rituximab in a well-controlled trial confirms previous preliminary reports indicating that B cell depletion can treat established autoimmune disease.

B cell depletion therapy in systemic lupus erythematosus

There is a growing body of experimental evidence that B lymphocytes play a central role in the pathogenesis of systemic lupus erythematosus (SLE). B cells are, by definition, the precursors of antibody-secreting cells, and thus are the source of pathogenic autoantibodies. However, recent data indicate that B cells are not merely the passive producers of immunoglobulins, but also play a central role in autoimmunity via nonconventional mechanisms, including autoantigen presentation and modulation of other immune cells. Thus, B lymphocyte depletion has recently emerged as a promising therapeutic approach to the treatment of autoimmune diseases, including SLE. Rituximab is a chimeric mouse-human monoclonal antibody against the B cell-specific antigen CD20, which selectively and profoundly depletes B lymphocytes and has been widely used to treat B cell lymphomas. Recent open-label studies indicate that rituximab is safe and may be efficacious in the treatment of SLE, and continued study with randomized clinical trials is justified.

Down-regulation of CD20 on B cells upon CD40 activation

CD20 is a B cell-specific surface antigen that is thought to play an important role in B cell activation and proliferation, possibly by functioning as a calcium channel or interacting with other cell surface molecules important in B cell signal transduction, such as CD40. In this study, it was found that stimulation through CD40 caused a dramatic decrease in the expression of surface CD20 in normal human B lymphocytes. Down-regulation of CD20 was time and ligand concentration dependent, beginning as early as 15 min after incubation with CD40 ligand-transfected fibroblasts. The rapid onset of this effect in the presence of stable steady-state mRNA levels suggests that CD20 down-regulation occurs at a nontranscriptional level. Confocal fluorescent microscopy indicates that CD20 and CD40 are internalized upon CD40 activation. Specifically, CD20 translocates into lipid rafts and is internalized into cytoplasmic vesicles, in a process that is inhibited by cytochalasin B and protein kinase C antagonists. Paradoxically, one functional consequence of CD20 down-regulation was enhanced calcium signaling upon CD20 cross-linking. These observations support the notion that CD20 engages downstream signaling pathways that alter calcium homeostasis rather than functioning as a calcium channel itself, such signal transduction is enhanced upon CD20 internalization, and CD40 is a regulator of CD20-mediated signaling.