Imaging of fetal thymus in pregnant women with rheumatic diseases.

OBJECTIVE: To determine whether certain rheumatic diseases will affect the fetal thymus diameter when compared to uncomplicated singleton pregnancies. Additionally, we created a reference chart for fetal thymus size in healthy singleton pregnancies from 19 to 37 weeks of gestation. METHODS: Sonographic fetal thymus size was retrospectively evaluated in 190 healthy pregnant women, and 84 pregnancies of mothers suffering from systemic lupus erythematosus, antiphospholipid syndrome (APS), or Sjögren's syndrome between 19 and 37 weeks of gestation. These fetuses were matched one-to-one for gestational age with control fetuses. The thymic-thoracic ratio (TT-ratio) was defined as the quotient of the anteroposterior thymic and the intrathoracic mediastinal diameter. RESULTS: Rheumatic diseases often affect pregnancy outcome, especially in case of primary APS. The TT ratio of fetuses of mothers suffering from rheumatic disease was equal to controls (P=0.807). CONCLUSIONS: Ours is the first study to assess the correlation of fetal thymus size in high-risk pregnancies with rheumatic diseases in comparison to controls. Women with rheumatic diseases deal with pregnancy complications more frequently than controls. Our data suggest that maternal rheumatic diseases do not affect the fetal thymus size.

Mycophenolic acid counteracts B cell proliferation and plasmablast formation in patients with systemic lupus erythematosus.

INTRODUCTION: Clinical trials revealed a high efficacy of mycophenolate mofetil (MMF)in inducing and maintaining remission in patients with class III-V-lupus nephritis. Also extrarenal manifestations respond to MMF treatment. However, few attempts have been undertaken to delineate its mechanism of action in systemic lupus erythematosus (SLE) a disease characterized by enhanced B cell activation. METHODS: Clinical and paraclinical parameters of 107 patients with SLE were recorded consecutively and analyzed retrospectively. Patients were divided into treatment groups (MMF: n=39, azathioprine (AZA) n=30 and controls without immunosuppressive therapy n=38). To further delineate the effect of mycophenolic acid (MPA) on naive and memory B cells in vitro assays were performed. RESULTS: Although patients taking AZA flared more frequently than patients on MMF or controls, the analysis of clinical parameters did not reveal significant differences.However, profound differences in paraclinical parameters were found. B cell frequencies and numbers were significantly higher in patients taking MMF compared to those on AZA but lower numbers and frequencies of plasmablasts were detected compared to AZA-treated patients or controls. Notably, MMF treatment was associated with a significantly higher frequency and number of transitional B cells as well as naive B cells compared to AZA treatment. Differences in T cell subsets were not significant. MPA abrogated in vitro proliferation of purified B cells completely but had only moderate impact on B cell survival. CONCLUSIONS: The thorough inhibition of B cell activation and plasma cell formation by MMF might explain the favorable outcomes of previous clinical trials in patients with SLE, since enhanced B cell proliferation is a hallmark of this disease.

Cardioprotective effect of calcineurin inhibition in an animal model of renal disease.

AIMS: Chronic kidney disease is directly associated with cardiovascular complications. Heart remodelling, including fibrosis, hypertrophy, and decreased vascularization, is frequently present in renal diseases. Our objective was to investigate the impact of calcineurin inhibitors (CNI) on cardiac remodelling and function in a rat model of renal disease. METHODS AND RESULTS: Male Sprague Dawley rats were divided into six groups: sham-operated rats, 5/6 nephrectomized rats (Nx) treated with vehicle, CNI (cyclosporine A 5.0 or 7.5, or tacrolimus 0.5 mg/kg/day) or hydralazine (20 mg/kg twice a day) for 14 days, starting on the day of surgery. Creatinine clearance was significantly lower and blood pressure significantly higher in Nx rats when compared with controls. Morphological and echocardiographic analyses revealed increased left ventricular hypertrophy and decreased number of capillaries in Nx rats. Treatment with CNI affected neither the renal function nor the blood pressure, but prevented the development of cardiac hypertrophy and improved vascularization. In addition, regional blood volume improved as confirmed by contrast agent-based echocardiography. Hydralazine treatment did not avoid heart remodelling in this model. Gene expression analysis verified a decrease in hypertrophic genes in the heart of CNI-treated rats, while pro-angiogenic and stem cell-related genes were upregulated. Moreover, mobilization of stem/progenitor cells was increased through manipulation of the CD26/SDF-1 system. CONCLUSION: We conclude from our studies that CNI-treatment significantly prevented cardiac remodelling and improved heart function in Nx rats without affecting renal function and blood pressure. This sheds new light on possible therapeutic strategies for renal patients at high cardiovascular risk.

Abnormalities of B cell subsets in patients with systemic lupus erythematosus.

The prototypic autoimmune disease, SLE, is known to be associated with polyclonal B cell hyperreactivity. Developing an understanding of the complex nature of human B cell differentiation, largely through the application of multiparameter flow cytometry to an analysis of circulating B cells has permitted an assessment of whether specific stages of B cell maturation are affected by the tendency for polyclonal B cell activation. Moreover, the analysis of perturbations of the specific stages of B cell maturation has generated new information on whether abnormalities in B cell differentiation are primarily involved in autoimmune disease immunopathology or, rather, are secondary to the inflammatory environment characteristic of subjects with this autoimmune disease. Multivariant analysis has begun to document abnormalities in B cell maturation that are primarily associated with lupus, or, alternatively related to disease duration, disease activity and concomitant medication. Together, these analyses have provided new insights on the role of B cell over-reactivity in SLE.

Current aspects of anti-CD20 therapy in rheumatoid arthritis.

Although B cells represent major contributors to rheumatoid arthritis (RA) pathogenesis, their precise roles in the induction and maintenance of abnormal immune activation in this entity remains poorly understood. As proof of principle, rituximab, a chimeric B cell depleting anti-CD20-antibody, has demonstrated that depletion of B cells can substantially improve signs and symptoms as well as physical function and inhibit radiologic progression that led to the approval of this agent to treat patients with moderate to severe RA lacking response to TNF-alpha blocking agents in 2006. Placebo-controlled clinical trials as well as subsequent studies and experiences further contributed to our understanding of the mechanism of action of rituximab, but a number of open questions remain. This review summarizes some lessons learned from B cell depletion in RA including particular safety aspects. Of importance using this therapy is that it apparently provides the highest likelihood of response in seropositive RA patients. This observation differentiates it from other currently available therapies and closes the conceptual loop that the underlying immunopathogenesis involves B cells requiring 'targeted' therapy.

Effect of long-term belimumab treatment on B cells in systemic lupus erythematosus: extension of a phase II, double-blind, placebo-controlled, dose-ranging study.

OBJECTIVE: To understand the effects of long-term BLyS inhibition in human systemic lupus erythematosus (SLE). METHODS: Seventeen patients with SLE who were enrolled in a clinical trial of belimumab, a BLyS-specific inhibitor, plus standard of care therapy were studied. Phenotypic analysis of lymphocytes was performed using flow cytometry. Circulating antibody-secreting cells were enumerated using enzyme-linked immunospot assay. Serum was analyzed by enzyme-linked immunosorbent assay using an antibody that recognizes products of the V(H)4-34 gene. Lymphocyte counts, Ig levels, and anti-double-stranded DNA antibody levels were available as part of the clinical trial analyses. RESULTS: Samples were collected on days 0, 84, 168, 365, and 532 and after day 730. The total number of B cells started to decrease from baseline between days 84 and 168. This was due to a decrease in naive and transitional B cells. CD27+IgD+ memory B cells and plasmablasts decreased only after 532 days, whereas CD27+IgD- memory B cells were not affected, and there were no changes in T cells. Serum IgM levels began to decline between days 84 and 168, but there were no changes in serum levels of IgG, IgG anti-DNA antibodies, or V(H)4-34 antibodies during the study. SLE patients had more IgM-, IgG-, and autoantibody-producing B cells than did normal controls on day 0. There was only a modest decrease in the frequency of total IgM-producing, but not IgG-producing, cells on days 365 and 532, consistent with the phenotypic and serologic data. CONCLUSION: Our data confirm the dependence of newly formed B cells on BLyS for survival in humans. In contrast, memory B cells and plasma cells are less susceptible to selective BLyS inhibition.

B cells in autoimmunity.

B-cell development is tightly regulated, including the induction of B-cell memory and antibody-secreting plasmablasts and plasma cells. In the last decade, we have expanded our understanding of effector functions of B cells as well as their roles in human autoimmune diseases. The current review addresses the role of certain stages of B-cell development as well as plasmablasts/plasma cells in immune regulation under normal and autoimmune conditions with particular emphasis on systemic lupus erythematosus. Based on preclinical and clinical data, B cells have emerged increasingly as both effector cells as well as cells with immunoregulatory potential.

Phenotypic characterization of autoreactive B cells--checkpoints of B cell tolerance in patients with systemic lupus erythematosus.

DNA-reactive B cells play a central role in systemic lupus erythematosus (SLE); DNA antibodies precede clinical disease and in established disease correlate with renal inflammation and contribute to dendritic cell activation and high levels of type 1 interferon. A number of central and peripheral B cell tolerance mechanisms designed to control the survival, differentiation and activation of autoreactive B cells are thought to be disturbed in patients with SLE. The characterization of DNA-reactive B cells has, however, been limited by their low frequency in peripheral blood. Using a tetrameric configuration of a peptide mimetope of DNA bound by pathogenic anti-DNA antibodies, we can identify B cells producing potentially pathogenic DNA-reactive antibodies. We, therefore, characterized the maturation and differentiation states of peptide, (ds) double stranded DNA cross-reactive B cells in the peripheral blood of lupus patients and correlated these with clinical disease activity. Flow cytometric analysis demonstrated a significantly higher frequency of tetramer-binding B cells in SLE patients compared to healthy controls. We demonstrated the existence of a novel tolerance checkpoint at the transition of antigen-naïve to antigen-experienced. We further demonstrate that patients with moderately active disease have more autoreactive B cells in both the antigen-naïve and antigen-experienced compartments consistent with greater impairment in B cell tolerance in both early and late checkpoints in these patients than in patients with quiescent disease. This methodology enables us to gain insight into the development and fate of DNA-reactive B cells in individual patients with SLE and paves the way ultimately to permit better and more customized therapies.

Polyreactive autoantibodies in systemic lupus erythematosus have pathogenic potential.

The present study was undertaken to determine whether germline encoded and polyreactive antibodies might be pathogenic and whether the breach of early tolerance checkpoints in systemic lupus erythematosus (SLE) might lead to a population of B cells expressing germline encoded antibodies that become pathogenic merely by class switching to IgG in a pro-inflammatory milieu. We demonstrate here that IgM, DNA-reactive antibodies obtained from lupus patients that are unmutated and display polyreactivity can bind to isolated glomeruli and exhibit neurotoxic potential. Thus, the IgM polyreactive repertoire in SLE includes antibodies that may acquire pathogenic function merely by undergoing class-switch recombination to become IgG antibodies.

Pathogenic autoantibodies in systemic lupus erythematosus are derived from both self-reactive and non-self-reactive B cells.

Previous studies have shown that both murine and human anti-double-stranded DNA (anti-dsDNA) antibodies can develop from non-DNA-reactive B cells and suggest a crucial role for somatic mutation in dsDNA binding. However, since only a limited number of human anti-dsDNA antibodies have been analyzed previously, we could not exclude other mechanisms for the generation of anti-dsDNA antibodies in patients with systemic lupus erythematosus (SLE). Therefore, we isolated IgM anti-dsDNA antibodies from peripheral blood B cells of a patient with SLE. Three somatically mutated IgM anti-DNA antibodies with pathogenic potential (glomerular binding) were reverted to their germline configuration. Although all three IgM anti-dsDNA antibodies came from the same lupus patient, they displayed different profiles. Reversion to the germline sequence of autoantibodies A9 and B5 resulted in decreased dsDNA binding. In contrast, the germline form of G3-recognized dsDNA as well as the mutated counterpart. These results suggest that mutated IgM anti-dsDNA antibodies may develop from both DNA- and non-DNA-reactive B cells. The implications are that B cell activation occurs in response to self and non-self antigens, while selection after activation may be mediated by self antigen in SLE. Moreover, ineffective tolerance checkpoints may exist before and after antigen activation in SLE.

Identification of DNA-reactive B cells in patients with systemic lupus erythematosus.

Autoreactive B cells play a central role in systemic lupus erythematosus (SLE). Characterization of DNA-reactive B cells in the blood of lupus patients has been limited by the low frequency of the population. Using a tetrameric configuration of a peptide mimetope of DNA, we identified peptide-reactive B cells in peripheral blood. Antibodies derived from these B cells bound to peptide and were largely cross-reactive to dsDNA. This methodology enables us to track the development of autoreactive B cells, which recognize peptide and dsDNA, in individual patients with SLE and permits the isolation of autoreactive B cells for further characterization.

Activated memory B cell subsets correlate with disease activity in systemic lupus erythematosus: delineation by expression of CD27, IgD, and CD95.

OBJECTIVE: Analysis of peripheral B cell subsets in patients with systemic lupus erythematosus (SLE) has provided evidence of specific alterations, such as an expansion of CD27++ plasma cells/blasts and transitional B cells. However, memory B cells in lupus have not been thoroughly investigated, and only recently a CD27- memory B cell subset was identified in the peripheral blood of lupus patients. Focusing on CD27- B cells, this study aimed to identify abnormalities in peripheral B cell subsets in patients with SLE. METHODS: Three independent cohorts of lupus patients were used to characterize CD27- memory B cells, using multiparameter flow cytometry and single-cell reverse transcription-polymerase chain reaction of heavy-chain transcripts. RESULTS: We identified a homogeneous subset of CD27-,IgD-,CD95+ memory B cells with an activated phenotype that was increased in patients with disease flares and that correlated with disease activity and serologic abnormalities. In contrast, the entire subset of CD27-,IgD- B cells was found to be heterogeneous, did not correlate significantly with lupus activity, and was also increased in patients with bacterial infections. CONCLUSION: We conclude that CD95 is a useful marker to identify CD27- memory B cells with an activated phenotype, which might serve as a biomarker for lupus activity and as a target of further investigations aiming to elucidate the pathogenic potential of these cells and the mechanisms involved in the generation as well as regulation of this CD27-,IgD-,CD95+ memory B cell subset.

Balancing diversity and tolerance: lessons from patients with systemic lupus erythematosus.

The autoimmune disease systemic lupus erythematosus (SLE) is caused by a failure of B cell tolerance. Recent studies in mouse models of SLE have identified several distinct tolerance checkpoints that must each function appropriately to protect against disease. However, studies of B cell repertoire selection in humans are essential to understand which checkpoints are defective in human autoimmune diseases.

Generation of migratory antigen-specific plasma blasts and mobilization of resident plasma cells in a secondary immune response.

Maintenance of protective humoral immunity depends on the generation and survival of antibody-secreting cells. The bone marrow provides niches for long-term survival of plasma cells generated in the course of systemic immune responses in secondary lymphoid organs. Here, we have analyzed migratory human plasma blasts and plasma cells after secondary vaccination with tetanus toxin. On days 6 and 7 after immunization, CD19(+)/CD27(high)/intracellular immunoglobulin G(high) (IgG(high))/HLA-DR(high)/CD38(high)/CD20(-)/CD95(+) tetanus toxin-specific antibody-secreting plasma blasts were released in large numbers from the secondary lymphoid organs into the blood. These cells show chemotactic responsiveness toward ligands for CXCR3 and CXCR4, probably guiding them to the bone marrow or inflamed tissue. At the same time, a population of CD19(+)/CD27(high)/intracellular IgG(high)/HLA-DR(low)/CD38(+)/CD20(-)/CD95(+) cells appeared in the blood in large numbers. These cells, with the phenotype of long-lived plasma cells, secreted antibodies of unknown specificity, not tetanus toxoid. The appearance of these plasma cells in the blood indicates successful competition for survival niches in the bone marrow between newly generated plasma blasts and resident plasma cells as a fundamental mechanism for the establishment of humoral memory and its plasticity.

Correlation between circulating CD27high plasma cells and disease activity in patients with systemic lupus erythematosus.

OBJECTIVE: Disease activity in systemic lupus erythematosus (SLE) is usually assessed with complex disease activity scores comprising a variety of different parameters. In order to determine whether SLE disease activity correlates with abnormal B lymphocyte activity, B cell subsets were analyzed, and their relationship to clinical and humoral measures of disease activity was assessed. METHODS: The distribution of B cell subsets was determined by fluorescence-activated cell sorting analysis and assessed in relation to the autoantibody profile, disease activity measured by the SLE Disease Activity Index (SLEDAI) and the European Consensus Lupus Activity Measure scores, disease duration, and therapy. RESULTS: The number and frequency of CD27(high) plasma cells were significantly correlated with the SLE disease activity indices and with the titer of anti-double-stranded DNA (anti-dsDNA) autoantibodies. Circulating B cell subsets were not influenced by age or sex, but appeared to relate to the duration of disease and the therapeutic regimen, with the number and frequency of CD27(high) plasma cells increasing and those of CD27- naive B cells decreasing over time. Patients were divided into those with a SLEDAI score of 0-8 (low disease activity) and those with SLEDAI score >8 (high disease activity). Patients with high disease activity had an increased frequency of both CD19+ B cells and CD27(high) plasma cells. By using a nonparametric data sieving algorithm, we observed that these B cell abnormalities provided predictive values for nonactive and active disease of 78.0% and 78.9%, respectively. The predictive value of the B cell abnormalities (78.9%) was greater than that of the humoral/clinical data pattern (71.4%), including anti-dsDNA antibody levels, circulating immune complexes, increased erythrocyte sedimentation rate, mucocutaneous involvement, and acute renal involvement. CONCLUSION: Flow cytometric monitoring of B cell subsets in the peripheral blood provides new insights into abnormalities of B cell function in SLE and may also be a diagnostically valuable option for monitoring the activity of this autoimmune disease.

Diminished peripheral blood memory B cells and accumulation of memory B cells in the salivary glands of patients with Sjögren's syndrome.

OBJECTIVE: To delineate the mechanism of the abnormalities in B cell biology found in patients with primary Sjögren's syndrome (SS). METHODS: The distribution of peripheral B cell subpopulations in 21 patients with primary SS was analyzed by immunofluorescence labeling and flow cytometry. Immunoglobulin rearrangements were analyzed in single B cells isolated from the peripheral blood and parotid glands by fluorescence-activated cell sorting. RESULTS: A significant reduction in the number of peripheral CD27+ memory B cells was found in SS patients, including a significantly reduced number of CD27+/IgD+/IgM+/CD5+ memory B cells. Remarkably, SS patients with secondary lymphoma uniquely exhibited an increase in CD27-expressing peripheral B cells, including CD27(high) plasmablasts. Molecular analysis for mutated Ig gene rearrangements confirmed that CD27 expression distinguished naive and memory cells in SS. In contrast to the peripheral blood, the majority of parotid B cells from 1 patient examined exhibited both the mutational status and phenotype of memory B cells. Accordingly, the mutational frequencies of V(H) rearrangements were significantly greater in parotid B cells than in peripheral blood B cells, whereas the V(H) gene repertoire appeared to be very similar between the compartments. CONCLUSION: These data indicate that there is an accumulation/retention of memory B cells in the inflamed salivary glands of SS patients. It is possible that preferential accumulation of CD27+ memory B cells in the inflamed parotid gland explains their reduction in the peripheral blood.

Analysis of immunoglobulin light chain rearrangements in the salivary gland and blood of a patient with Sjögren's syndrome.

Patients with Sjögren's syndrome (SS) have characteristic lymphocytic infiltrates of the salivary glands. To determine whether the B cells accumulating in the salivary glands of SS patients represent a distinct population and to delineate their potential immunopathologic impact, individual B cells obtained from the parotid gland and from the peripheral blood were analyzed for immunoglobulin light chain gene rearrangements by PCR amplification of genomic DNA. The productive immunoglobulin light chain repertoire in the parotid gland of the SS patient was found to be restricted, showing a preferential usage of particular variable lambda chain genes (V lambda 2E) and variable kappa chain genes (V kappa A27). Moreover, clonally related V(L) chain rearrangements were identified; namely, V kappa A27-J kappa 5 and V kappa A19-J kappa 2 in the parotid gland, and V lambda 1C-J lambda 3 in the parotid gland and the peripheral blood. V kappa and V lambda rearrangements from the parotid gland exhibited a significantly elevated mutational frequency compared with those from the peripheral blood (P < 0.001). Mutational analysis revealed a pattern of somatic hypermutation similar to that found in normal donors, and a comparable impact of selection of mutated rearrangements in both the peripheral blood and the parotid gland. These data indicate that there is biased usage of V(L) chain genes caused by selection and clonal expansion of B cells expressing particular V(L) genes. In addition, the data document an accumulation of B cells bearing mutated V(L) gene rearrangements within the parotid gland of the SS patient. These results suggest a role of antigen-activated and selected B cells in the local autoimmune process in SS.