B cell abnormalities in systemic lupus erythematosus

Vitamin D3: a helpful immuno-modulator

The active metabolite of vitamin D, 1α, 25-dihydroxyvitamin D3 [1,25(OH)(2) D3], is involved in calcium and phosphate metabolism and exerts a large number of biological effects. Vitamin D3 inhibits parathyroid hormone secretion, adaptive immunity and cell proliferation, and at the same time promotes insulin secretion, innate immunity and stimulates cellular differentiation. The role of vitamin D3 in immunoregulation has led to the concept of a dual function as both as an important secosteroid hormone for the regulation of body calcium homeostasis and as an essential organic compound that has been shown to have a crucial effect on the immune responses. Altered levels of vitamin D3 have been associated, by recent observational studies, with a higher susceptibility of immune-mediated disorders and inflammatory diseases. This review reports the new developments with specific reference to the metabolic and signalling mechanisms associated with the complex immune-regulatory effects of vitamin D3 on immune cells.

B cell signature during inactive systemic lupus is heterogeneous: toward a biological dissection of lupus

Systemic lupus erythematosous (SLE) is an autoimmune disease with an important clinical and biological heterogeneity. B lymphocytes appear central to the development of SLE which is characterized by the production of a large variety of autoantibodies and hypergammaglobulinemia. In mice, immature B cells from spontaneous lupus prone animals are able to produce autoantibodies when transferred into immunodeficient mice, strongly suggesting the existence of intrinsic B cell defects during lupus. In order to approach these defects in humans, we compared the peripheral B cell transcriptomas of quiescent lupus patients to normal B cell transcriptomas. When the statistical analysis is performed on the entire group of patients, the differences between patients and controls appear quite weak with only 14 mRNA genes having a false discovery rate ranging between 11 and 17%, with 6 underexpressed genes (PMEPA1, TLR10, TRAF3IP2, LDOC1L, CD1C and EGR1). However, unforced hierarchical clustering of the microarrays reveals a subgroup of lupus patients distinct from both the controls and the other lupus patients. This subgroup has no detectable clinical or immunological phenotypic peculiarity compared to the other patients, but is characterized by 1/an IL-4 signature and 2/the abnormal expression of a large set of genes with an extremely low false discovery rate, mainly pointing to the biological function of the endoplasmic reticulum, and more precisely to genes implicated in the Unfolded Protein Response, suggesting that B cells entered an incomplete BLIMP1 dependent plasmacytic differentiation which was undetectable by immunophenotyping. Thus, this microarray analysis of B cells during quiescent lupus suggests that, despite a similar lupus phenotype, different biological roads can lead to human lupus.

Ets-1: a new player in the pathogenesis of systemic lupus erythematosus?

v-ets erythroblastosis virus E26 oncogene homolog 1 (avian) (Ets-1) is a member of the Ets family of transcription factors that share a unique Ets DNA binding domain. They control a wide variety of cellular processes including cell proliferation and differentiation. Recently, two genome-wide association studies in systemic lupus erythematosus (SLE) independently identified genetic variants in Ets-1 associated with SLE. Interestingly, previous studies have found that Ets-1-deficient mice develop lupus-like disease characterized by high titers of IgM and IgG autoantibodies, immune complex-mediated glomerulonephritis, and local activation of complement. In addition, Ets-1 is also involved in many cellular abnormalities that are known to participate in SLE pathogenesis, such as its role in negative regulation of Th17 cell and B cell differentiation. All these findings suggest that Ets-1 may play an important role in the pathogenesis of SLE. This article will focus on current understanding of the role of Ets-1 in the physiological and pathological functions associated with SLE. It is the intention of the article to provide insights which may assist in the development of Ets-1 based approaches for the treatment of SLE.

Elevated serum level of circulating syndecan-1 (CD138) in active systemic lupus erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE) is characterized by loss of B cell tolerance and by the presence of polyclonal B cell activation. Syndecan-1 (CD138) is expressed on plasma cells derived from B cells, and is suspected to play a role in SLE. We evaluated the level of soluble CD138 (sCD138) and cell surface expression of CD138 in patients with active SLE, and also examined correlations among the serum levels of BAFF, a proliferation-inducing ligand (APRIL), and CD138 in these patients.

METHODS

Peripheral blood samples were obtained from 22 SLE patients in an active disease state and 14 normal controls. The levels of serum sCD138, sBAFF, and sAPRIL were measured using ELISA, and cell surface CD138 was analyzed by flow cytometry. The levels of CD138 mRNA were analyzed by RT-PCR. Blood samples were obtained longitudinally when the patients were in an inactive disease state.

RESULTS

The levels of circulating CD138, CD138 mRNA in PBMC, and the numbers of CD20(- )CD38(+)CD138(+) plasma cells were increased in patients with active SLE in comparison with normal controls. Furthermore, the serum sCD138 level in SLE patients was found to correlate with the proportion of CD20(- )CD38(+)CD138(+) plasma cells. On the other hand, patients with active SLE showed a reduced level of sCD138, and this was inversely correlated with the serum level of sAPRIL.

CONCLUSIONS

These results suggest that sCD138 may be applicable as a surrogate marker of disease activity, and that syndecan-1/APRIL signaling may be a potential therapeutic target for patients with active SLE.

Inhibition of a C-rich oligodeoxynucleotide on activation of immune cells in vitro and enhancement of antibody response in mice

To explore the possibility that human mitochondrial genomic DNA-mimicking oligodeoxynucleotides could regulate the immune response, a series of mitochondrial DNA-based oligodeoxynucleotides (MTODNs) were designed and studied to determine their immunoregulatory effects on immune cells activated by toll-like receptor (TLR) stimulation. The results showed that a C-rich MTODN, designated MT01, was able to inhibit the proliferation of human peripheral blood mononuclear cells (PBMCs) induced by cytosine-phosphate-guanosine (CpG) oligodeoxynucleotides (ODNs) and the production of type I interferon (IFN) from human PBMCs stimulated by TLR agonists, including inactivated influenza virus, imiquimod, inactivated herpes simplex virus-1 (HSV-1) and CpG ODNs. In addition, MT01 inhibited the CpG ODN-enhanced antibody response and this inhibition could be related to the antagonism of TLR9-activation pathways in B cells. Notably, unlike the G-rich suppressive ODNs reported, MT01 is composed of ACCCCCTCT repeats. These data imply that MT01 represents a novel class of immunosuppressive ODNs that could be candidate biologicals with therapeutic use in TLR activation-associated diseases.

A role for the B-cell CD74/macrophage migration inhibitory factor pathway in the immunomodulation of systemic lupus erythematosus by a therapeutic tolerogenic peptide

Systemic lupus erythematosus (SLE) is an autoimmune disease that involves dysregulation of B and T cells. A tolerogenic peptide, designated hCDR1, ameliorates disease manifestations in SLE-afflicted mice. In the present study, the effect of treatment with hCDR1 on the CD74/macrophage migration inhibitory factor (MIF) pathway was studied. We report here that B lymphocytes from SLE-afflicted mice express relatively elevated levels of CD74, compared with B cells from healthy mice. CD74 is a receptor found in complex with CD44, and it binds the pro-inflammatory cytokine MIF. The latter components were also up-regulated in B cells from the diseased mice, and treatment with hCDR1 resulted in their down-regulation and in reduced B-cell survival. Furthermore, up-regulation of CD74 and CD44 expression was detected in brain hippocampi and kidneys, two target organs in SLE. Treatment with hCDR1 diminished the expression of those molecules to the levels determined for young healthy mice. These results suggest that the CD74/MIF pathway plays an important role in lupus pathology.

Off-label use of rituximab in systemic lupus erythematosus: a systematic review

Considerable interest in the efficacy of rituximab (a monoclonal CD20 antibody) in patients with systemic lupus erythematosus (SLE) has been generated due to its unique mode of action, culminating in a series of randomized and open trials, and case reports. However, this use is off-license and two significant RCTs have reported negative findings, reopening the debate on clinical benefit. This review of the available data suggests that rituximab induces B-cell depletion in 95% of patients, and a significant reduction in disease activity is achieved with a relatively good safety profile in patients with SLE.

Genome-wide association study in Asian populations identifies variants in ETS1 and WDFY4 associated with systemic lupus erythematosus

Systemic lupus erythematosus is a complex and potentially fatal autoimmune disease, characterized by autoantibody production and multi-organ damage. By a genome-wide association study (320 patients and 1,500 controls) and subsequent replication altogether involving a total of 3,300 Asian SLE patients from Hong Kong, Mainland China, and Thailand, as well as 4,200 ethnically and geographically matched controls, genetic variants in ETS1 and WDFY4 were found to be associated with SLE (ETS1: rs1128334, P = 2.33×10⁻¹¹, OR = 1.29; WDFY4: rs7097397, P = 8.15×10⁻¹², OR = 1.30). ETS1 encodes for a transcription factor known to be involved in a wide range of immune functions, including Th17 cell development and terminal differentiation of B lymphocytes. SNP rs1128334 is located in the 3′-UTR of ETS1, and allelic expression analysis from peripheral blood mononuclear cells showed significantly lower expression level from the risk allele. WDFY4 is a conserved protein with unknown function, but is predominantly expressed in primary and secondary immune tissues, and rs7097397 in WDFY4 changes an arginine residue to glutamine (R1816Q) in this protein. Our study also confirmed association of the HLA locus, STAT4, TNFSF4, BLK, BANK1, IRF5, and TNFAIP3 with SLE in Asians. These new genetic findings may help us to gain a better understanding of the disease and the functions of the genes involved.

In this study, we first conducted a genome-wide association study in a Hong Kong Chinese population, followed by replication in three other cohorts from Mainland China and a cohort from Thailand, which totaled 3,300 Asian patients and 4,200 ethnically and geographically matched controls. We identified novel variants in ETS1 and WDFY4 associated with SLE with genome-wide significance and confirmed the association of HLA locus, STAT4, BLK, IRF5, BANK1, TNFSF, and IRF5 with the disease. ETS1 encodes a critical transcription factor involved in Th17 and B cell development. Allelic expression study showed a significantly lower expression of ETS1 from the risk allele, which provided functional support to the genetic findings. WDFY4 is a huge protein with unknown function but is predominantly expressed in primary and secondary immune tissues, and a nonsynonymous SNP in this gene was found to be highly associated with SLE susceptibility. Our findings shed new light on the function of these genes as well as the mechanism of this devastating disease.

B-cell biology and related therapies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex disease characterized by numerous autoantibodies and clinical involvement in multiple organ systems. The immunologic events triggering the onset and progression of clinical manifestations have not yet been fully defined, but a central role for B cells in the pathogenesis has been brought to the fore in the last several years. The breakdown of B-cell tolerance is likely a defining and early event in the disease process and may occur by multiple pathways, including alterations in factors that affect B-cell activation thresholds, B-cell longevity, and apoptotic cell processing. Antibody-dependent and -independent mechanisms of B cells are important in SLE. Thus, autoantibodies contribute to autoimmunity by multiple mechanisms including immune complex mediated type III hypersensitivity reactions, type II antibody-dependent cytotoxicity, and by instructing innate immune cells to produce pathogenic cytokines including interferon alpha, tumor necrosis factor, and interleukin 1. Recent data have highlighted the critical role of toll-like receptors as a link between the innate and adaptive immune system in SLE immunopathogenesis. Given the large body of evidence implicating abnormalities in the B-cell compartment in SLE, there has been a therapeutic focus on developing interventions that target the B-cell compartment. Several different approaches to targeting B cells have been used, including B-cell depletion with monoclonal antibodies against B-cell-specific molecules, induction of negative signaling in B cells, and blocking B-cell survival and activation factors. Overall, therapies targeting B cells are beginning to show promise in the treatment of SLE and continue to elucidate the diverse roles of B cells in this complex disease.

CD19(+)CD24(hi)CD38(hi) B cells exhibit regulatory capacity in healthy individuals but are functionally impaired in systemic Lupus Erythematosus patients

The immunosuppressive function of regulatory B cells has been shown in several murine models of chronic inflammation, including collagen-induced arthritis, inflammatory bowel disease, and experimental autoimmune encephalomyelitis. Despite interest in these cells, their relevance to the maintenance of peripheral tolerance in humans remains elusive. Here, we demonstrate that human CD19(+)CD24(hi)CD38(hi) B cells possessed regulatory capacity. After CD40 stimulation, CD19(+)CD24(hi)CD38(hi) B cells suppressed the differentiation of T helper 1 cells, partially via the provision of interleukin-10 (IL-10), but not transforming growth factor-beta (TGF-beta), and their suppressive capacity was reversed by the addition of CD80 and CD86 mAbs. In addition, CD19(+)CD24(hi)CD38(hi) SLE B cells isolated from the peripheral blood of systemic lupus erythematosus (SLE) patients were refractory to further CD40 stimulation, produced less IL-10, and lacked the suppressive capacity of their healthy counterparts. Altered cellular function within this compartment may impact effector immune responses in SLE and other autoimmune disorders.

The role of B cells in lupus pathogenesis

Autoantibodies clearly contribute to tissue inflammation in systemic lupus erythematosus. In order to therapeutically target B cells making pathogenic autoantibodies, it is necessary to identify their phenotype. It is also important to understand the defects in B cell repertoire selection that permit pathogenic autoreactive B cells to enter the immunocompetent B cell repertoire. We present the data that both marginal zone and follicular B cells can produce pathogenic autoantibodies. Moreover, we discuss how B cell survival and maturation are regulated centrally prior to antigen activation and in the periphery after antigen activation to form the repertoire that generates the spectrum of circulating antibodies.

A tolerogenic peptide down-regulates mature B cells in bone marrow of lupus-afflicted mice by inhibition of interleukin-7, leading to apoptosis

Systemic lupus erythematosus (SLE) is an autoimmune disease mediated by T and B cells. It is characterized by a variety of autoantibodies and systemic clinical manifestations. A tolerogenic peptide, designated hCDR1, ameliorated the serological and clinical manifestations of SLE in both spontaneous and induced models of lupus. In the present study, we evaluated the status of mature B cells in the bone marrow (BM) of SLE-afflicted mice, and determined the effect of treatment with the tolerogenic peptide hCDR1 on these cells. We demonstrate herein that mature B cells of the BM of SLE-afflicted (New Zealand Black x New Zealand White)F(1) mice were largely expanded, and that treatment with hCDR1 down-regulated this population. Moreover, treatment with hCDR1 inhibited the expression of the pathogenic cytokines [interferon-gamma and interleukin (IL)-10], whereas it up-regulated the expression of transforming growth factor-beta in the BM. Treatment with hCDR1 up-regulated the rates of apoptosis of mature B cells. The latter was associated with inhibited expression of the survival Bcl-xL gene and of IL-7 by BM cells. Furthermore, the addition of recombinant IL-7 abrogated the suppressive effects of hCDR1 on Bcl-xL in the BM cells and resulted in elevated levels of apoptosis. Hence, the down-regulated production of IL-7 contributes to the hCDR1-mediated apoptosis of mature B cells in the BM of SLE-afflicted mice.

Raised expression of cytokine receptor gp130 subunit on peripheral lymphocytes of patients with active lupus. A useful tool for monitoring the disease activity?

The glycoprotein gp130 is a signal traducing subunit with a membrane domain of the IL-6 receptor. In addition, gp130 is shared among the receptors for IL-6 superfamily, and it is critically involved in generating signal transduction through these receptors. The aim of the study is to evaluate the expression of the IL-6 superfamily receptor molecule gp130 on TCD4(+) and B cells in patients with systemic lupus erythematosus (SLE). Surface expression of gp130 on TCD4(+) and B lymphocytes was higher in patients with SLE than in healthy controls (2.79 vs 0.36% and 8.36 vs 0.37%, respectively). Patients with active lupus had higher expression of gp130 (relapsed 15.1%, new onset 26.6%) than stable patients (2.83%), in B-cell subset, but not in TCD4 lymphocytes. An important reduction in the gp130 expression on B lymphocytes was observed when the activity of the disease had disappeared after readjusting its immunosuppressive treatment (20.8-3.8%). In addition, there was significant correlation between the activity of the disease, measured like systemic lupus erythematosus disease activity index score, and surface expression of gp130 in lymphocytes B (r(s) = 0.5880, P = 0.0002). According with our results and roc curve analysis, a cut-off in 6.7% of B cells with gp130 expression were defined, who discriminates active/stable SLE with a sensitivity of 0.93 and a specificity of 0.75. In conclusion, there is an altered expression of gp130 in the patients with SLE. The disease activity as well as immunotherapy seems to influence the pattern of expression of gp130 on B-cell subsets in patients with SLE.

Proteomic analysis of plasma from patients with systemic lupus erythematosus: increased presence of haptoglobin alpha2 polypeptide chains over the alpha1 isoforms

In the present study plasma samples from 15 systemic lupus erythematosus (SLE) patients and 16 healthy controls of initially unknown haptoglobin (Hp) phenotype were separated by 2-DE, and tryptic digests of the excised Hpalpha polypeptide chain spots were analyzed by MALDI-TOF-MS. Selected tryptic peptides were sequenced by nano-(n)ESI-IT MS/MS. The six major Hp phenotypes were present, although with distinct frequencies in controls and SLE patients. Thus, there were an increased proportion of SLE patients with Hp 2-2, or Hp 2-1S phenotypes. The Hp phenotype distribution resulted in allele frequencies of 0 625 (Hp(2)), 0.281 (Hp(1S)), and 0.093 (Hp(1F)) in healthy controls, correlating fairly well with the allele frequencies of European populations. In contrast, the Hp allele frequencies of the SLE patients were 0.733 (Hp(2)), 0.233 (Hp(1S)), and 0.033 (Hp1(1F)), which clearly indicated an increased frequency of Hp(2), a similar proportion of Hp(1S) and a diminished proportion of Hp(1F) in SLE patients compared with that in healthy controls. Preferential Hpalpha2 expression in SLE patients may contribute to some of the clinical manifestations of the disease such as hypergammaglobulinemia, systemic vasculitis, and cardiovascular disorders.

TACI, an enigmatic BAFF/APRIL receptor, with new unappreciated biochemical and biological properties

BAFF is a B cell survival factor that binds to three receptors BAFF-R, TACI and BCMA. BAFF-R is the receptor triggering naïve B cell survival and maturation while BCMA supports the survival of plasma cells in the bone marrow. Excessive BAFF production leads to autoimmunity, presumably as the consequence of inappropriate survival of self-reactive B cells. The function of TACI has been more elusive with TACI(-/-) mice revealing two sides of this receptor, a positive one driving T cell-independent immune responses and a negative one down-regulating B cell activation and expansion. Recent work has revealed that the regulation of TACI expression is intimately linked to the activation of innate receptors on B cells and that TACI signalling in response to multimeric BAFF and APRIL provides positive signals to plasmablasts. How TACI negatively regulates B cells remains elusive but may involve an indirect control of BAFF levels. The discovery of TACI mutations associated with common variable immunodeficiency (CVID) in humans not only reinforces its important role for humoral responses but also suggests a more complex role than first anticipated from knockout animals. TACI is emerging as an unusual TNF receptor-like molecule with a sophisticated mode of action.

Targeting of the immune system in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex immune disorder in which loss of tolerance to nucleic acid antigens and other crossreactive antigens is associated with the development of pathogenic autoantibodies that damage target organs, including the skin, joints, brain and kidney. New drugs based on modulation of the immune system are currently being developed for the treatment of SLE. Many of these new therapies do not globally suppress the immune system but target specific activation pathways relevant to SLE pathogenesis. Immune modulation in SLE is complicated by differences in the immune defects between patients and at different disease stages. Since both deficiency and hyperactivity of the immune system can give rise to SLE, the ultimate goal for SLE therapy is to restore homeostasis without affecting protective immune responses to pathogens. Here we review recent immunological advances that have enhanced our understanding of SLE pathogenesis and discuss how they may lead to the development of new treatment regimens.

A longitudinal analysis of SLE patients treated with rituximab (anti-CD20): factors associated with B lymphocyte recovery

Identifying factors associated with B lymphocyte depletion and recovery may aid the development of individualized treatment regimens, optimizing therapy for patients with autoimmune disease. In this study, 12 patients with active SLE were monitored at baseline and monthly following treatment with rituximab. The number and phenotype of peripheral blood B lymphocytes, T lymphocytes and natural killer cells were correlated with the extent and longevity of B lymphocyte depletion. This analysis generated three candidate biomarkers for lymphocyte monitoring in patients with autoimmune disease who are treated with rituximab: circulating transitional B cells, the kappa:lambda ratio and natural killer cells. Further refinement of these potential biomarkers may lead to a better understanding of the role of B cells in disease pathogenesis and a more rational use of B cell depletion therapies.

Cytokine gene polymorphisms in Colombian patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) patients exhibit alterations in cytokine production that may be relevant to SLE pathogenesis. There is evidence that cytokine gene polymorphisms control cytokine production; thus, these polymorphisms may be associated with SLE or its clinical manifestations. To establish the association of tumor necrosis factor alpha (TNF-alpha), transforming growth factor (TGF) beta1, interleukin (IL)-10, and IL-6 gene polymorphisms in Colombian SLE patients and their clinical manifestations, 120 SLE patients and 102 healthy controls were studied. Single nucleotide polymorphisms were studied by sequence-specific primers polymerase chain reaction (SSP-PCR) at: TNFalpha-308 (G/A), TGFbeta1 codon 10 (C/T) and codon 25 (G/C), IL-10 -1082 (G/A), -819 (C/T) and -592 (C/A), and IL-6 + 174 (G/C). Human leukocyte antigen (HLA)-DRbeta1 was typed by SSP-PCR. SLE patients had increased frequency of allele C at TGFbeta1 codon 25 (P = 0.0001, odds ratio (OR): 4.25, 95% confidence interval (CI): 2.17-8.35) and allele A at TNFalpha-308 (P = 0.0004 OR: 3.9, 95% CI: 1.65-5.80) compared with healthy controls. There was higher frequency of GC genotype at TGFbeta1 codon 25 in SLE patients (P < 0.0001). Extended genotypic analysis showed that SLE patients have decreased frequency of TNFalphaLow/TGFbeta1High (0.50) compared with healthy controls (0.80) (P < 0.0001). No association was found between these polymorphisms and SLE clinical manifestations except for Sm and Ro autoantibodies that were associated with TNFalpha allele A. There is an association between TNFalpha-308A/TGFbeta1 codon 25C with SLE susceptibility in Colombian population. This association may result in a highly inflammatory response with a decrease regulatory function mediated by TNFalpha and TGFbeta1, respectively. The TNFalpha-308A/TGFbeta1 25C genotype may be one component of genetic susceptibility to SLE in Colombian population.

Modulatory effects of 1,25-dihydroxyvitamin D3 on human B cell differentiation

1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) can modulate immune responses, but whether it directly affects B cell function is unknown. Patients with systemic lupus erythematosus, especially those with antinuclear Abs and increased disease activity, had decreased 1,25(OH)(2)D(3) levels, suggesting that vitamin D might play a role in regulating autoantibody production. To address this, we examined the effects of 1,25(OH)(2)D(3) on B cell responses and found that it inhibited the ongoing proliferation of activated B cells and induced their apoptosis, whereas initial cell division was unimpeded. The generation of plasma cells and postswitch memory B cells was significantly inhibited by 1,25(OH)(2)D(3), although the up-regulation of genetic programs involved in B cell differentiation was only modestly affected. B cells expressed mRNAs for proteins involved in vitamin D activity, including 1 alpha-hydroxylase, 24-hydroxylase, and the vitamin D receptor, each of which was regulated by 1,25(OH)(2)D(3) and/or activation. Importantly, 1,25(OH)(2)D(3) up-regulated the expression of p27, but not of p18 and p21, which may be important in regulating the proliferation of activated B cells and their subsequent differentiation. These results indicate that 1,25(OH)(2)D(3) may play an important role in the maintenance of B cell homeostasis and that the correction of vitamin D deficiency may be useful in the treatment of B cell-mediated autoimmune disorders.

Analysis of expression and function of the inhibitory receptor ILT2 (CD85j/LILRB1/LIR-1) in peripheral blood mononuclear cells from patients with systemic lupus erythematosus (SLE)

The aim of this work was to study the expression and function of the inhibitory receptor ILT2/CD85j in peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus (SLE). We studied 23 SLE patients as well as 17 patients with rheumatoid arthritis, 10 with fibromyalgia, and 23 healthy individuals. We found a variable level of expression of ILT2 in the PBMC from both SLE patients and controls, with no significant differences among them. However, when the expression of this receptor was assessed in cell subsets, significantly lower levels were detected in CD19+ lymphocytes from SLE patients compared with healthy controls. Functional assays performed in unfractionated PBMC, showed a significant diminished inhibitory activity of ILT2 in CD4+ and CD8+ cell subsets from SLE patients compared to either rheumatoid arthritis or fibromyalgia patients, and healthy individuals. Our results show that the PBMC from some patients with SLE show a defective expression of ILT2, and that most of them exhibit a poor function of this inhibitory receptor.

BAFF and MyD88 signals promote a lupuslike disease independent of T cells

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the production of autoantibodies. However, the underlying cause of disease appears to relate to defects in T cell tolerance or T cell help to B cells. Transgenic (Tg) mice overexpressing the cytokine B cell–activating factor of the tumor necrosis factor family (BAFF) develop an autoimmune disorder similar to SLE and show impaired B cell tolerance and altered T cell differentiation. We generated BAFF Tg mice that were completely deficient in T cells, and, surprisingly, these mice developed an SLE-like disease indistinguishable from that of BAFF Tg mice. Autoimmunity in BAFF Tg mice did, however, require B cell–intrinsic signals through the Toll-like receptor (TLR)–associated signaling adaptor MyD88, which controlled the production of proinflammatory autoantibody isotypes. TLR7/9 activation strongly up-regulated expression of transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI), which is a receptor for BAFF involved in B cell responses to T cell–independent antigens. Moreover, BAFF enhanced TLR7/9 expression on B cells and TLR-mediated production of autoantibodies. Therefore, autoimmunity in BAFF Tg mice results from altered B cell tolerance, but requires TLR signaling and is independent of T cell help. It is possible that SLE patients with elevated levels of BAFF show a similar basis for disease.

11th annual Inflammatory and Immune Diseases Drug Discovery and Development Summit 12-13 March 2007, San Francisco, USA

The Strategic Research Institute (SRi) hosted the 11th International Inflammation and Immune Diseases Drug Discovery and Development World Summit in San Francisco during 12-13 March 2007. The summit comprised keynote sessions and two parallel tracks and focussed on targeting mechanisms for drug discovery and development, which modulate the immune response and which have anti-inflammatory activity in a number of human diseases. Indications included psoriasis, hepatitis C, allergic dermatitis, systemic lupus erythematosus, rheumatoid arthritis and osteoarthritis, multiple sclnerosis, cardiovascular disease and asthma. Data were presented supporting all stages of drug discovery from target identification and validation through to lead identification and optimisation to both early- and late-stage clinical development.

Possible therapeutic applications of single-chain antibodies in systemic autoimmune diseases

B cells participate in the induction and maintenance of systemic autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus, via production of pathogenic autoantibodies, contributing to the formation of immune complexes. Immune complex deposition in the kidney and joints causes inflammation and organ destruction, and chemokine production enhances T cell activation and tissue damage. The development of the disorder depends on several factors, for example, genetic susceptibility, environmental factors or immune dysregulation. Traditional therapies, which aimed at the alleviation of symptoms, are giving way to biological therapies with the potential of disrupting disease progression. This article focuses on antibody therapies, especially on the applications of single-chain antibodies, as new biological agents for the treatment of systemic autoimmune disorders.

T cells and B cells in lupus nephritis

T and B lymphocytes play diverse roles at multiple stages in the development and progression of lupus nephritis. Disruption of T- and B-cell regulatory functions by environmental and genetic influences permits pathogenic effectors to emerge in disease. New insights into the biology of these multifunctional cells offer novel targets for intervention in lupus nephritis and systemic autoimmunity.

Treatment with rituximab affects both the cellular and the humoral arm of the immune system in patients with SLE

Herein we investigated how rituximab-induced B cell depletion affected leukocyte subpopulations and antibody titers in SLE patients. We focused our analysis on time points related to absence and return of B cells after depletion. A correlation was found between the baseline frequency and time to repopulation; the fewer B cells initially, the longer to their return. While the few B cells remaining after treatment were of memory, double-negative (IgD-CD27-), and CD5+ phenotype, the returning B cells were mainly naïve, indicating de novo production of B cells. Serum levels of IgG and antibodies against Ro52, Ro60, La44, measles and tetanus remained unchanged, while decreases in IgM, IgE, anti-dsDNA and anti-C1q antibodies were observed. Additionally, a significant increase in activated CD4+ and CD8+ T cells, as well as CD25bright FOXP3+ regulatory T cells was observed. In conclusion, both the humoral and the cellular immune systems were affected by treatment with rituximab.

Naive CD4 T cells constitutively express CD40L and augment autoreactive B cell survival

Chronic engagement of the B cell receptor by soluble autoantigen leads to reduced B cell survival. Using the Ig and hen egg lysozyme double transgenic mouse model, we demonstrate that the survival of soluble autoantigen-engaged B cells is further reduced in mice lacking CD4 T cells or deficient in CD40. Mixed bone marrow chimera experiments reveal that, under homeostatic conditions, the CD40L-CD40 pathway can augment autoreactive B cell survival in a non-cell-autonomous manner. Naive CD4 T cells are shown to constitutively express CD40L mRNA and protein, although cell surface CD40L abundance is low because of engagement with CD40 on other cells. These observations indicate that the CD40L-CD40 pathway can augment the survival of autoantigen-engaged B cells in the absence of T cell activation. We propose that constitutive CD40L expression by naive CD4 T cells influences the composition of the B cell repertoire and may also affect the homeostasis of other cell types such as regulatory T cells in lymphoid organs.

Rituximab therapy for childhood-onset systemic lupus erythematosus

OBJECTIVE

To describe the safety and efficacy of rituximab in the treatment of childhood-onset systemic lupus erythematosus (SLE).

STUDY DESIGN

We conducted a French multicenter retrospective study of childhood-onset SLE treated with rituximab.

RESULTS

Eleven girls with severe SLE, including 8 girls with class IV or V lupus nephritis, 2 girls with severe autoimmune cytopenia, and 1 girl with antiprothrombin antibody with severe hemorrhage, were treated with rituximab. The mean age at onset of rituximab treatment was 13.9 years. Patients received 2 to 12 intravenous infusions of rituximab (350-450 mg/m2/infusion), with corticosteroids. Six patients also received different standard immunosuppressive agents, including Cyclophosphamide (2 patients). Remission was achieved in 6 of 8 patients with lupus nephritis and in the 2 patients with autoimmune cytopenia. Steroid therapy was tapered in 5 patients who responded to treatment, and low-dose prednisone treatment was maintained in 1 patient. The mean follow-up period was 13.2 months (range, 6-26 months), and remission lasted in all who patients who responded to treatment, except 1 patient who was successfully retreated with a second course of rituximab. Anti-double-stranded DNA antibody levels decreased in 6 of 11 patients, and anticardiolipin antibody levels decreased in 3 of 4 patients. Severe adverse events developed in 5 patients. Effective depletion of peripheral blood B cells was observed in 7 of 8 patients who were examined, and this paralleled the remission.

CONCLUSION

Rituximab may be an effective co-therapy; however, further investigations are required because severe adverse events occurred in 45% of the patients in this study.

Increased association of CD38 with lipid rafts in T cells from patients with systemic lupus erythematosus and in activated normal T cells

In this study we have determined whether there is a relationship between CD38 expression on T cells, its distribution in different membrane microdomains, and T cell activation in SLE patients. The data show that CD38 expression is augmented in ex vivo CD3+, CD4+, CD8+, and CD25+ SLE T cells, which correlates with its increased insolubility in Brij 98 detergent, and its translocation into lipid rafts. Moreover, SLE T cells show an altered CD4:CD8 ratio, which is due to a decreased proportion of CD4+ T cells and a concomitant increase in the proportion of CD8+ T cells. These data are consistent with the increased CD38 expression and lipid raft formation, and the significant reduction in the CD4:CD8 ratio observed in mitogen-stimulated normal T cells as compared with that in ex vivo untouched normal T cells. Increased expression of CD38 in floating rafts from SLE T cells, or from activated normal T cells may modulate TCR signaling by providing or sequestering signaling molecules to the engaged TCR.

Similarities and differences between selective and nonselective BAFF blockade in murine SLE

B cells have multiple roles in immune activation and inflammation separate from their capacity to produce antibodies. B cell depletion is currently under intense investigation as a therapeutic strategy for autoimmune diseases. The TNF family members B cell-activating factor of the TNF family (BAFF) and its homolog A proliferation-inducing ligand (APRIL) are B cell survival and differentiation factors and are therefore rational therapeutic targets. We compared the effects of BAFF receptor-Ig, which blocks only BAFF, with those of transmembrane activator and calcium modulator ligand interactor-Ig, which blocks both BAFF and APRIL, in a murine SLE model. Both reagents prolonged the life of NZB/W F1 mice when given either before or after disease onset. Many immunologic effects of the 2 reagents were similar, including B cell and B cell subset depletion and prevention of the progressive T cell activation and dendritic cell accumulation that occurs with age in NZB/W mice without substantial effects on the emergence of the IgG anti-double-stranded DNA response. Furthermore, both reagents inhibited the T cell-independent marginal zone B cell response to particulate antigen delivered i.v., but not the B1 B cell response to the same antigen delivered i.p. In contrast, blockade of both BAFF and APRIL, but not blockade of BAFF alone, reduced the serum levels of IgM antibodies, decreased the frequency of plasma cells in the spleen, and inhibited the IgM response to a T cell-dependent antigen. The differences between selective and nonselective BAFF blockade are relevant to the choice of a BAFF blocking agent for the treatment of autoimmune and malignant diseases.

Challenges in bringing the bench to bedside in drug development for sle

It is now widely accepted that the current standard of care for systemic lupus erythematosus (SLE) patients is inadequate. There has not been a new medication approved for this disease in thirty years. Attempts to develop and test new drugs have been ongoing since the mid-1990s, but have encountered formidable obstacles. Current models for lupus pathogenesis have provided a theoretical framework for understanding how heterogeneous genetic defects might combine in various ways to increase susceptibility to SLE in different individuals, and could have important implications for new drug development. With the current burst of drug discovery and increased public awareness of SLE, the impetus to overcome these obstacles has never been greater.