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1.  Mycophenolic acid counteracts B cell proliferation and plasmablast formation in patients with systemic lupus erythematosus 
Arthritis Research & Therapy  2012;14(3):R110.
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.
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.
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.
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.
PMCID: PMC4060361  PMID: 22571761
2.  The Effect of Prolonged Treatment with Belimumab on B cells in Human SLE 
Arthritis and rheumatism  2010;62(1):201-210.
To understand the effects of prolonged BLyS inhibition in human SLE.
17 SLE patients 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 ELISpot assay. Serum was analyzed by ELISA using an antibody that recognizes products of the VH4-34 gene. Lymphocyte counts, Ig levels and anti-dsDNA antibody levels were available as part of the clinical trial analyses.
Samples were collected at days 0, 84, 168, 365, 532 and >730. The total B cell number decreased from baseline starting between days 84–168. This was due to a decrease in naïve 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 84–168, but there were no changes in serum levels of IgG, IgG anti-DNA antibodies or VH4-34 antibodies during the study. SLE patients had more IgM-, IgG-, and autoantibody-producing B cells than normal controls at Day 0. There was only a modest decrease in the frequency of total IgM-producing but not IgG-producing cells at Days 365 and 532, consistent with the phenotypic and serologic data.
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.
PMCID: PMC2857977  PMID: 20039404
3.  Polyreactive autoantibodies in systemic lupus erythematosus have pathogenic potential 
Journal of autoimmunity  2009;33(3-4):270-274.
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.
PMCID: PMC2783480  PMID: 19398190
4.  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.
PMCID: PMC2787254  PMID: 19849820
5.  Identification of DNA-reactive B cells in Patients with Systemic Lupus Erythematosus 
Journal of immunological methods  2008;338(1-2):79-84.
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.
PMCID: PMC2577778  PMID: 18713638
lupus; B cells; immunoglobulins; peptide
6.  Phenotypic Characterization of Autoreactive B Cells—Checkpoints of B Cell Tolerance in Patients with Systemic Lupus Erythematosus 
PLoS ONE  2009;4(6):e5776.
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.
PMCID: PMC2685013  PMID: 19488401
7.  Pathogenic Autoantibodies in Systemic Lupus Erythematosus Are Derived from Both Self-Reactive and Non-Self–Reactive B Cells 
Molecular Medicine  2008;14(11-12):675-681.
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.
PMCID: PMC2493535  PMID: 18677426
8.  Balancing diversity and tolerance 
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.
PMCID: PMC2213089  PMID: 16061723
9.  Analysis of immunoglobulin light chain rearrangements in the salivary gland and blood of a patient with Sjögren's syndrome 
Arthritis Research  2002;4(4):R4.
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 immunglobulin light chain gene rearrangements by PCR amplification of genomic DNA. The productive immunglobulin 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 (Vλ2E) and variable kappa chain genes (VκA27). Moreover, clonally related VL chain rearrangements were identified; namely, VκA27–Jκ5 and VκA19–Jκ2 in the parotid gland, and Vλ1C–Jλ3 in the parotid gland and the peripheral blood. Vκ and Vλ 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 VL chain genes caused by selection and clonal expansion of B cells expressing particular VL genes. In addition, the data document an accumulation of B cells bearing mutated VL 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.
PMCID: PMC125296  PMID: 12106503
B cells; parotid gland; Sjögren's syndrome; somatic mutation; V light chain genes

Results 1-9 (9)