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1.  Polymorphisms in the Hsp70 gene locus are genetically associated with systemic lupus erythematosus 
Annals of the Rheumatic Diseases  2010;69(11):1983-1989.
Heat shock proteins (Hsps) play a role in the delivery and presentation of antigenic peptides and are thought to be involved in the pathogenesis of multifactorial diseases.
To investigate genes encoding cytosolic Hsp70 proteins for associations of allelic variants with systemic lupus erythematosus (SLE).
Case–control studies of two independent Caucasian SLE cohorts were performed. In a haplotype-tagging single-nucleotide polymorphism approach, common variants of HspA1L, HspA1A and HspA1B were genotyped and principal component analyses were performed for the cohort from the Oklahoma Medical Research Foundation (OMRF). Relative quantification of mRNA was carried out for each Hsp70 gene in healthy controls. Conditional regression analysis was performed to determine if allelic variants in Hsp70 act independently of HLA-DR3.
On analysis of common genetic variants of HspA1L, HspA1A and HspA1B, a haplotype significantly associated with SLE in the Erlangen-SLE cohort was identified, which was confirmed in the OMRF cohort. Depending on the cohorts, OR ranging from 1.43 to 1.88 and 2.64 to 3.16 was observed for individuals heterozygous and homozygous for the associated haplotype, respectively. Patients carrying the risk haplotype or the risk allele more often displayed autoantibodies to Ro and La in both cohorts. In healthy controls bearing this haplotype, the amount of HspA1A mRNA was significantly increased, whereas total Hsp70 protein concentration was not altered.
Allelic variants of the Hsp70 genes are significantly associated with SLE in Caucasians, independently of HLA-DR3, and correlate with the presence of autoantibodies to Ro and La. Hence, the Hsp70 gene locus appears to be involved in SLE pathogenesis.
PMCID: PMC3002760  PMID: 20498198
2.  The proteasome inhibitior bortezomib depletes plasma cells and ameliorates clinical manifestations of refractory systemic lupus erythematosus 
Annals of the Rheumatic Diseases  2015;74(7):1474-1478.
To investigate whether bortezomib, a proteasome inhibitor approved for treatment of multiple myeloma, induces clinically relevant plasma cell (PC) depletion in patients with active, refractory systemic lupus erythematosus (SLE).
Twelve patients received a median of two (range 1–4) 21-day cycles of intravenous bortezomib (1.3 mg/m2) with the coadministration of dexamethasone (20 mg) for active SLE. Disease activity was assessed using the SLEDAI-2K score. Serum concentrations of anti–double-stranded DNA (anti-dsDNA) and vaccine-induced protective antibodies were monitored. Flow cytometry was performed to analyse peripheral blood B-cells, PCs and Siglec-1 expression on monocytes as surrogate marker for type-I interferon (IFN) activity.
Upon proteasome inhibition, disease activity significantly declined and remained stable for 6 months on maintenance therapies. Nineteen treatment-emergent adverse events occurred and, although mostly mild to moderate, resulted in treatment discontinuation in seven patients. Serum antibody levels significantly declined, with greater reductions in anti-dsDNA (∼60%) than vaccine-induced protective antibody titres (∼30%). Bortezomib significantly reduced the numbers of peripheral blood and bone marrow PCs (∼50%), but their numbers increased between cycles. Siglec-1 expression on monocytes significantly declined.
These findings identify proteasome inhibitors as a putative therapeutic option for patients with refractory SLE by targeting PCs and type-I IFN activity, but our results must be confirmed in controlled trials.
PMCID: PMC4484251  PMID: 25710470
Systemic Lupus Erythematosus; Autoimmune Diseases; B cells; Treatment; Autoimmunity
3.  The protein tyrosine phosphatase PTP1B is a negative regulator of CD40 and BAFF-R signaling and controls B cell autoimmunity 
The protein tyrosine phosphatase PTP1B regulates co-receptor signaling on B cells and thus controls B cell autoimmunity.
Tyrosine phosphorylation of signaling molecules that mediate B cell activation in response to various stimuli is tightly regulated by protein tyrosine phosphatases (PTPs). PTP1B is a ubiquitously expressed tyrosine phosphatase with well-characterized functions in metabolic signaling pathways. We show here that PTP1B negatively regulates CD40, B cell activating factor receptor (BAFF-R), and TLR4 signaling in B cells. Specifically, PTP1B counteracts p38 mitogen-activated protein kinase (MAPK) activation by directly dephosphorylating Tyr182 of this kinase. Mice with a B cell–specific PTP1B deficiency show increased T cell–dependent immune responses and elevated total serum IgG. Furthermore, aged animals develop systemic autoimmunity with elevated serum anti-dsDNA, spontaneous germinal centers in the spleen, and deposition of IgG immune complexes and C3 in the kidney. In a clinical setting, we observed that B cells of rheumatoid arthritis patients have significantly reduced PTP1B expression. Our data suggest that PTP1B plays an important role in the control of B cell activation and the maintenance of immunological tolerance.
PMCID: PMC3949573  PMID: 24590766
4.  High Levels of SOX5 Decrease Proliferative Capacity of Human B Cells, but Permit Plasmablast Differentiation 
PLoS ONE  2014;9(6):e100328.
Currently very little is known about the differential expression and function of the transcription factor SOX5 during B cell maturation. We identified two new splice variants of SOX5 in human B cells, encoding the known L-SOX5B isoform and a new shorter isoform L-SOX5F. The SOX5 transcripts are highly expressed during late stages of B-cell differentiation, including atypical memory B cells, activated CD21low B cells and germinal center B cells of tonsils. In tonsillar sections SOX5 expression was predominantly polarized to centrocytes within the light zone. After in vitro stimulation, SOX5 expression was down-regulated during proliferation while high expression levels were permissible for plasmablast differentiation. Overexpression of L-SOX5F in human primary B lymphocytes resulted in reduced proliferation, less survival of CD138neg B cells, but comparable numbers of CD138+CD38hi plasmablasts compared to control cells. Thus, our findings describe for the first time a functional role of SOX5 during late B cell development reducing the proliferative capacity and thus potentially affecting the differentiation of B cells during the germinal center response.
PMCID: PMC4063782  PMID: 24945754
5.  Rituximab in the treatment of refractory or relapsing eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome) 
Arthritis Research & Therapy  2013;15(5):R133.
Eosinophilic granulomatosis with polyangiitis (EGPA) is part of antineutrophil cytoplasmic antibodies (ANCAs)-associated vasculitides. In EGPA small-vessel vasculitis is associated with eosinophilia and asthma. About 40% of EGPA patients are ANCA-positive, suggesting a role for B cells in the pathogenesis of EGPA. B cell-depleting therapy with rituximab (RTX) can be effective in ANCA-positive EGPA, but very few patients have been published to date. The role of RTX in the treatment of ANCA-negative EGPA is unclear.
We report a single-center cohort of patients with eosinophilic granulomatosis with polyangiitis. Of these patients, nine (six ANCA-positive, three ANCA-negative) had been treated with RTX for relapsing or refractory disease on standard immunosuppressive treatment. In a retrospective analysis, data on treatment response, frequency of relapses, adverse events, and peripheral B-cell reconstitution were evaluated. Furthermore, serum immunoglobulin concentrations, ANCA status, and peripheral B cell subpopulations were assessed after RTX treatment.
All patients had high disease activity before RTX treatment. At presentation 3 months after RTX therapy, all ANCA-positive and ANCA-negative patients had responded to RTX, with one patient being in complete remission, and eight patients being in partial remission. After a mean follow-up of 9 months, C-reactive protein concentrations had normalized, eosinophils had significantly decreased, and prednisone had been tapered in all patients. In all patients, RTX therapy was combined with a standard immunosuppressive therapy. Within the 9-month observation period, no relapse was recorded. Three patients were preemptively retreated with RTX, and during the median follow-up time of 3 years, no relapse occurred in these patients. During the follow-up of 13 patient-years, five minor but no major infections were recorded.
In our analysis on nine patients with EGPA resistant to standard therapy, rituximab proved to be an efficient and safe treatment for ANCA-positive and ANCA-negative patients. Preemptive retreatment with RTX, combined with standard maintenance immunosuppressants, resulted in a sustained treatment response. Prospective, randomized trials evaluating the use of RTX in EGPA are warranted.
PMCID: PMC3979021  PMID: 24286362
6.  Impact of Rituximab on Immunoglobulin Concentrations and B Cell Numbers after Cyclophosphamide Treatment in Patients with ANCA-Associated Vasculitides 
PLoS ONE  2012;7(5):e37626.
To assess the impact of immunosuppressive therapy with cyclophosphamide (CYC) and rituximab (RTX) on serum immunoglobulin (Ig) concentrations and B lymphocyte counts in patients with ANCA-associated vasculitides (AAVs).
Retrospective analysis of Ig concentrations and peripheral B cell counts in 55 AAV patients.
CYC treatment resulted in a decrease in Ig levels (median; interquartile range IQR) from IgG 12.8 g/L (8.15-15.45) to 9.17 g/L (8.04-9.90) (p = 0.002), IgM 1.05 g/L (0.70-1.41) to 0.83 g/L (0.60-1.17) (p = 0.046) and IgA 2.58 g/L (1.71-3.48) to 1.58 g/L (1-31-2.39) (p = 0.056) at a median follow-up time of 4 months. IgG remained significantly below the initial value at 14.5 months and 30 months analyses. Subsequent RTX treatment in patients that had previously received CYC resulted in a further decline in Ig levels from pre RTX IgG 9.84 g/L (8.71-11.60) to 7.11 g/L (5.75-8.77; p = 0.007), from pre RTX IgM 0.84 g/L (0.63-1.18) to 0.35 g/L (0.23-0.48; p<0.001) and from pre RTX IgA 2.03 g/L (1.37-2.50) to IgA 1.62 g/L (IQR 0.84-2.43; p = 0.365) 14 months after RTX. Treatment with RTX induced a complete depletion of B cells in all patients. After a median observation time of 20 months median B lymphocyte counts remained severely suppressed (4 B-cells/µl, 1.25-9.5, p<0.001). Seven patients (21%) that had been treated with CYC followed by RTX were started on Ig replacement because of severe bronchopulmonary infections and serum IgG concentrations below 5 g/L.
In patients with AAVs, treatment with CYC leads to a decline in immunoglobulin concentrations. A subsequent RTX therapy aggravates the decline in serum immunoglobulin concentrations and results in a profoundly delayed B cell repopulation. Surveying patients with AAVs post CYC and RTX treatment for serum immunoglobulin concentrations and persisting hypogammaglobulinemia is warranted.
PMCID: PMC3357389  PMID: 22629432
7.  Pathogenesis of autoimmunity in common variable immunodeficiency 
Common variable immunodeficiency (CVID) presents in up to 25% of patients with autoimmune (AI) manifestations. Given the frequency and early onset in some patients with CVID, AI dysregulation seems to be an integral part of the immunodeficiency. Antibody-mediated AI cytopenias, most often affecting erythrocytes and platelets make up over 50% of these patients. This seems to be distinct from mainly cell-mediated organ-specific autoimmunity. Some patients present like patients with AI lymphoproliferative syndrome. Interestingly, in the majority of patients with AI cytopenias the immunological examination reveals a dysregulated B and T cell homeostasis. These phenotypic changes are associated with altered signaling through the antigen receptor which may well be a potential risk factor for disturbed immune tolerance as has been seen in STIM1 deficiency. In addition, elevated B cell-activating factor serum levels in CVID patients may contribute to survival of autoreactive B cells. Of all genetic defects associated with CVID certain alterations in TACI, CD19, and CD81 deficiency have most often been associated with AI manifestations. In conclusion, autoimmunity in CVID offers opportunities to gain insights into general mechanisms of human autoimmunity.
PMCID: PMC3399211  PMID: 22826712
autoimmune cytopenia;  autoimmunity; CD21low B cells; common variable immunodeficiency; hypogammaglobulinemia
9.  Cell-Intrinsic NF-κB Activation Is Critical for the Development of Natural Regulatory T Cells in Mice 
PLoS ONE  2011;6(5):e20003.
Naturally occurring CD4+CD25+Foxp3+ regulatory T (Treg) cells develop in the thymus and represent a mature T cell subpopulation critically involved in maintaining peripheral tolerance. The differentiation of Treg cells in the thymus requires T cell receptor (TCR)/CD28 stimulation along with cytokine-promoted Foxp3 induction. TCR-mediated nuclear factor kappa B (NF-κB) activation seems to be involved in differentiation of Treg cells because deletion of components of the NF-κB signaling pathway, as well as of NF-κB transcription factors, leads to markedly decreased Treg cell numbers in thymus and periphery.
Methodology/Principal Findings
To investigate if Treg cell-intrinsic NF-κB activation is required for thymic development and peripheral homeostasis of Treg cells we used transgenic (Tg) mice with thymocyte-specific expression of a stable IκBα mutant to inhibit NF-κB activation solely within the T cell lineage. Here we show that Treg cell-intrinsic NF-κB activation is important for the generation of cytokine-responsive Foxp3− thymic Treg precursors and their further differentiation into mature Treg cells. Treg cell development could neither be completely rescued by the addition of exogenous Interleukin 2 (IL-2) nor by the presence of wild-type derived cells in adoptive transfer experiments. However, peripheral NF-κB activation appears to be required for IL-2 production by conventional T cells, thereby participating in Treg cell homeostasis. Moreover, pharmacological NF-κB inhibition via the IκB kinase β (IKKβ) inhibitor AS602868 led to markedly diminished thymic and peripheral Treg cell frequencies.
Our results indicate that Treg cell-intrinsic NF-κB activation is essential for thymic Treg cell differentiation, and further suggest pharmacological NF-κB inhibition as a potential therapeutic approach for manipulating this process.
PMCID: PMC3097234  PMID: 21625598
10.  Calcium Channel Blocker Verapamil Enhances Endoplasmic Reticulum Stress and Cell Death Induced by Proteasome Inhibition in Myeloma Cells12 
Neoplasia (New York, N.Y.)  2010;12(7):550-561.
The proteasome inhibitor bortezomib is clinically approved for the treatment of multiple myeloma. However, long-term remissions are difficult to achieve, and myeloma cells often develop secondary resistance to proteasome inhibitors. We recently demonstrated that the extraordinary sensitivity of myeloma cells toward bortezomib is dependent on their extensive immunoglobulin synthesis, thereby triggering the terminal unfolded protein response (UPR). Here, we investigated whether verapamil, an inhibitor of the multidrug resistance (MDR) gene product, can enhance the cytotoxicity of bortezomib. The combination of bortezomib and verapamil synergistically decreased the viability of myeloma cells by inducing cell death. Importantly, bortezomib-mediated activation of major UPR components was enhanced by verapamil. The combination of bortezomib and verapamil resulted in caspase activation followed by poly(ADP-ribose) polymerase cleavage, whereas nuclear factor κB (NF-κB) activity declined in myeloma cells. Also, we found reduced immunoglobulin G secretion along with increased amounts of ubiquitinylated proteins within insoluble fractions of myeloma cells when using the combination treatment. Verapamil markedly induced reactive oxygen species production and autophagic-like processes. Furthermore, verapamil decreased MDR1 expression. We conclude that verapamil increased the antimyeloma effect of bortezomib by enhancing ER stress signals along with NF-κB inhibition, leading to cell death. Thus, the combination of bortezomib with verapamil may improve the efficacy of proteasome inhibitory therapy.
PMCID: PMC2907581  PMID: 20651984
11.  Differential role of NF-κB in selection and survival of CD4 and CD8 thymocytes 
Immunity  2008;29(4):523-537.
Inhibition of NF-κB activity leads to a reduction in numbers of CD8+ single positive (SP) thymocytes suggesting a selective role for NF-κB in these cells. To further explore the role of NF-κB in SP thymocytes we utilized transgenic models that allow either inhibition or activation of NF-κB. We now show that activation of NF-κB plays an important role in the selection of MHC class I restricted, CD8 T-cells. Surprisingly NF-κB is not activated in positively selected CD4 thymocytes, and inhibition of NF-κB does not perturb positive or negative selection of CD4 cells. However, enforced activation of NF-κB using a constitutively active IκB kinase transgene leads to nearly complete deletion of CD4 cells by pushing positively selecting CD4 cells into negative selection. These studies therefore reveal a surprising difference of NF-κB activation in CD4 and CD8 thymocytes and suggest that NF-κB contributes to the establishment of thresholds of signaling that determine positive-negative selection of thymocytes.
PMCID: PMC2670481  PMID: 18957265
12.  Induction of inflammatory and immune responses by HMGB1–nucleosome complexes: implications for the pathogenesis of SLE 
The Journal of Experimental Medicine  2008;205(13):3007-3018.
Autoantibodies against double-stranded DNA (dsDNA) and nucleosomes represent a hallmark of systemic lupus erythematosus (SLE). However, the mechanisms involved in breaking the immunological tolerance against these poorly immunogenic nuclear components are not fully understood. Impaired phagocytosis of apoptotic cells with consecutive release of nuclear antigens may contribute to the immune pathogenesis. The architectural chromosomal protein and proinflammatory mediator high mobility group box protein 1 (HMGB1) is tightly attached to the chromatin of apoptotic cells. We demonstrate that HMGB1 remains bound to nucleosomes released from late apoptotic cells in vitro. HMGB1–nucleosome complexes were also detected in plasma from SLE patients. HMGB1-containing nucleosomes from apoptotic cells induced secretion of interleukin (IL) 1β, IL-6, IL-10, and tumor necrosis factor (TNF) α and expression of costimulatory molecules in macrophages and dendritic cells (DC), respectively. Neither HMGB1-free nucleosomes from viable cells nor nucleosomes from apoptotic cells lacking HMGB1 induced cytokine production or DC activation. HMGB1-containing nucleosomes from apoptotic cells induced anti-dsDNA and antihistone IgG responses in a Toll-like receptor (TLR) 2–dependent manner, whereas nucleosomes from living cells did not. In conclusion, HMGB1–nucleosome complexes activate antigen presenting cells and, thereby, may crucially contribute to the pathogenesis of SLE via breaking the immunological tolerance against nucleosomes/dsDNA.
PMCID: PMC2605236  PMID: 19064698
13.  Inhibition of Phosphatidylserine Recognition Heightens the Immunogenicity of Irradiated Lymphoma Cells In Vivo 
The Journal of Experimental Medicine  2004;200(9):1157-1165.
Strategies to enhance the immunogenicity of tumors are urgently needed. Although vaccination with irradiated dying lymphoma cells recruits a tumor-specific immune response, its efficiency as immunogen is poor. Annexin V (AxV) binds with high affinity to phosphatidylserine on the surface of apoptotic and necrotic cells and thereby impairs their uptake by macrophages. Here, we report that AxV preferentially targets irradiated lymphoma cells to CD8+ dendritic cells for in vivo clearance, elicits the release of proinflammatory cytokines and dramatically enhances the protection elicited against the tumor. The response was endowed with both memory, because protected animals rejected living lymphoma cells after 72 d, and specificity, because vaccinated animals failed to reject unrelated neoplasms. Finally, AxV–coupled irradiated cells induced the regression of growing tumors. These data indicate that endogenous adjuvants that bind to dying tumor cells can be exploited to target tumors for immune rejection.
PMCID: PMC2211859  PMID: 15504819
apoptosis; phagocytosis; cancer; adjuvants; dendritic cells

Results 1-13 (13)