Serum B-cell activating factor predicts prognosis in nasal type,extranodal NK/T cell lymphoma

B-cell activating factor (BAFF) plays important roles in a variety of lymphoid malignancies. Compared with healthy adults, patients with non-Hodgkin lymphoma had higher level of serum BAFF, and it corresponded with disease severity, response for therapy and clinical outcome. Latent membrane protein 1 (LMP1) encoded by Epstein-Barr virus (EBV) which is a known agent of nasal, extranodal NK/T cell lymphoma (ENKTCL) can switch the BAFF activating promoter leading to higher expression of BAFF in EBV-related tumor cells. However, the relationship between BAFF and ENKTCL has not been reported. Here we proposed a hypothesis that BAFF might play a regulatory role in ENKTCL development and maintenance. Our results showed that serum BAFF in ENKTCL patients was significantly higher than that in control group and negatively correlated with patients’ survival. It may be a valuable prognostic factor and deserved further study.     

The current status of targeting BAFF/BLyS for autoimmune diseases

It is increasingly recognized that B cells have multiple functions that contribute to the pathogenesis of autoimmunity. Specific targeting of B cells might therefore be an appropriate therapeutic intervention. The tumor necrosis factor-like molecule BAFF (BLyS) is a key B cell survival factor and its receptors are expressed on most peripheral B cells. Several different BAFF antagonists are under development and in early clinical trials. We review here the rationale for BAFF blockade, and its predicted mechanism of action in autoimmune diseases.     

Cigarette smoke inhibits BAFF expression and mucosal immunoglobulin A responses in the lung during influenza virus infection

Background

It is incompletely understood how cigarette smoke (CS) exposure affects lung mucosal immune responses during viral respiratory infections. B cell activating factor belonging to the tumor necrosis factor family (BAFF) plays an important role in the induction of secretory immunoglobulin A (S-IgA) which is the main effector of the mucosal immune system. We therefore investigated the effects of CS exposure on BAFF expression and S-IgA responses in the lung during influenza virus infection.

Methods

Mice were exposed to CS and/or infected with influenza virus. Bronchoalveolar lavage fluid and lung compartments were analyzed for BAFF expression, influenza-specific S-IgA level and histological changes. Lung B cells were isolated and the activation-induced cytidine deaminase (Aicda) expression was determined. BEAS-2B cells were treated with CS extract (CSE), influenza virus, interferon beta or N-acetylcysteine and BAFF expression was measured.

Results

CS inhibited BAFF expression in the lung, particularly after long-term exposure. BAFF and S-IgA levels were increased during influenza virus infection. Three-month CS exposure prior to influenza virus infection resulted in reduced BAFF and S-IgA levels in the lung as well as augmented pulmonary inflammation on day 7 after infection. Prior CS exposure also caused decreased Aicda expression in lung B cells during infection. Neutralization of BAFF in the lung resulted in reduced S-IgA levels during influenza virus infection. CSE inhibited virus-mediated BAFF induction in a dose-dependent manner in BEAS-2B cells, while this inhibition of BAFF by CSE was prevented by pretreatment with the antioxidant N-acetylcysteine.

Conclusions

Our findings indicate that CS may hinder early mucosal IgA responses in the lung during influenza virus infection through oxidative inhibition of BAFF, which might contribute to the increased incidence and severity of viral infections in smokers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0201-y) contains supplementary material, which is available to authorized users.     

BAFF在自身免疫性疾病方面的研究进展

自身免疫性疾病的特征是B细胞耐受丧失,B细胞激活因子（B cell activating factor belonging to theTNF family,BAFF）通过与受体结合,对B细胞的增殖、存活起重要作用。BAFF转基因小鼠易出现自身免疫性疾病。因此,拮抗或抑制BAFF的表达可能是治疗自身免疫性疾病的靶点。本文主要对BAFF在自身免疫性疾病方面的研究进展进行综述。     

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 na?ve 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.     

B cell-activating factor of the tumor necrosis factor family (BAFF) is expressed under stimulation by interferon in salivary gland epithelial cells in primary Sjögren's syndrome

B cell-activating factor (BAFF) has a key role in promoting B-lymphocyte activation and survival in primary Sj?gren's syndrome (pSS). The cellular origin of BAFF overexpression in salivary glands of patients with pSS is not fully known. We investigated whether salivary gland epithelial cells (SGECs), the main targets of autoimmunity in pSS, could produce and express BAFF. We used quantitative RT-PCR, ELISA and immunocytochemistry in cultured SGECs from eight patients with pSS and eight controls on treatment with IL-10, tumor necrosis factor alpha (TNF-alpha), IFN-alpha and IFN-gamma. At baseline, BAFF expression in SGECs was low in pSS patients and in controls. Treatment with IFN-alpha, IFN-gamma and TNF-alpha + IFN-gamma increased the level of BAFF mRNA in pSS patients (the mean increases were 27-fold, 25-fold and 62-fold, respectively) and in controls (mean increases 19.1-fold, 26.7-fold and 17.7-fold, respectively), with no significant difference between patients and controls. However, in comparison with that at baseline, stimulation with IFN-alpha significantly increased the level of BAFF mRNA in SGECs of pSS patients (p = 0.03) but not in controls (p = 0.2), which suggests that SGECs of patients with pSS are particularly susceptible to expressing BAFF under IFN-alpha stimulation. Secretion of BAFF protein, undetectable at baseline, was significantly increased after IFN-alpha and IFN-gamma stimulation both in pSS patients (40.8 +/- 12.5 (+/- SEM) and 47.4 +/- 18.7 pg/ml, respectively) and controls (24.9 +/- 8.0 and 9.0 +/- 3.9 pg/ml, respectively), with no significant difference between pSS and controls. Immunocytochemistry confirmed the induction of cytoplasmic BAFF expression after stimulation with IFN-alpha and IFN-gamma. This study confirms the importance of resident cells of target organs in inducing or perpetuating autoimmunity. Demonstrating the capacity of SGECs to express and secrete BAFF after IFN stimulation adds further information to the pivotal role of these epithelial cells in the pathogenesis of pSS, possibly after stimulation by innate immunity. Our results suggest that an anti-BAFF therapeutic approach could be particularly interesting in pSS.     

B cell-activating factor of the tumor necrosis factor family (BAFF) is expressed under stimulation by interferon in salivary gland epithelial cells in primary Sjögren's syndrome

B cell-activating factor (BAFF) has a key role in promoting B-lymphocyte activation and survival in primary Sjögren's syndrome (pSS). The cellular origin of BAFF overexpression in salivary glands of patients with pSS is not fully known. We investigated whether salivary gland epithelial cells (SGECs), the main targets of autoimmunity in pSS, could produce and express BAFF. We used quantitative RT-PCR, ELISA and immunocytochemistry in cultured SGECs from eight patients with pSS and eight controls on treatment with IL-10, tumor necrosis factor α (TNF-α), IFN-α and IFN-γ. At baseline, BAFF expression in SGECs was low in pSS patients and in controls. Treatment with IFN-α, IFN-γ and TNF-α + IFN-γ increased the level of BAFF mRNA in pSS patients (the mean increases were 27-fold, 25-fold and 62-fold, respectively) and in controls (mean increases 19.1-fold, 26.7-fold and 17.7-fold, respectively), with no significant difference between patients and controls. However, in comparison with that at baseline, stimulation with IFN-α significantly increased the level of BAFF mRNA in SGECs of pSS patients (p = 0.03) but not in controls (p = 0.2), which suggests that SGECs of patients with pSS are particularly susceptible to expressing BAFF under IFN-α stimulation. Secretion of BAFF protein, undetectable at baseline, was significantly increased after IFN-α and IFN-γ stimulation both in pSS patients (40.8 ± 12.5 (± SEM) and 47.4 ± 18.7 pg/ml, respectively) and controls (24.9 ± 8.0 and 9.0 ± 3.9 pg/ml, respectively), with no significant difference between pSS and controls. Immunocytochemistry confirmed the induction of cytoplasmic BAFF expression after stimulation with IFN-α and IFN-γ. This study confirms the importance of resident cells of target organs in inducing or perpetuating autoimmunity. Demonstrating the capacity of SGECs to express and secrete BAFF after IFN stimulation adds further information to the pivotal role of these epithelial cells in the pathogenesis of pSS, possibly after stimulation by innate immunity. Our results suggest that an anti-BAFF therapeutic approach could be particularly interesting in pSS.     

Selection and Identification of Aptamers Against B Cell Activating Factor

Systemic lupus erythematosus (SLE) is the most common autoimmune disease in China. B cell activating factor (BAFF) is an important target for the treatment and detection of SLE. It is of great significance to develop novel molecular recognition elements with high affinity for BAFF. In this study, artificial nucleic acid aptamers against BAFF were screened from a 78 nt single-stranded DNA random library by systematic evolution of ligands exponential enrichment (SELEX) in vitro based on several selection and amplification steps. Through ten rounds of selection, the aptamers with high specificity and affinity for BAFF were identified. After high-throughput sequencing, several aptamers were selected and further examined for binding affinity and specificity. The investigation by dot blotting, Eastern blotting analyses and enzyme-linked oligonucleotide assay (ELONA) showed that the aptamers Apt 7 and Apt 12 with dissociation constants of 241.00±19.75 nmol/L and 413.51±46.94 nmol/L were able to recognize BAFF specifically. After molecular docking analysis, Apt 7 was truncated to Apt 7～1, and the dissociation constant was 192.10±28.61 nmol/L. A sandwich ELONA using Apt 7～1 and BAFF antibodies was established to detect BAFF. The detection limit was estimated to be 0.227 nmol/L. This study provides new molecular recognition elements for the detection of BAFF and the study of antagonists.     

Neutrophils Contribute to Excess Serum BAFF Levels and Promote CD4+ T Cell and B Cell Responses in Lupus-Prone Mice

Despite increased frequencies of neutrophils found in autoimmune diseases such as systemic lupus erythematosus (SLE), how they contribute to disease pathogenesis and the mechanisms that affect the accumulation of neutrophils are poorly understood. The aim of this study was to identify factors in autoantibody-mediated autoimmunity that controls the accumulation of spleen resident neutrophils and to determine whether neutrophils contribute to abnormal B cell responses. Increased levels of the cytokine BAFF have been linked to loss of B cell tolerance in autoimmunity, but the cellular source responsible for excess BAFF is unknown. B cell maturation antigen (BCMA) is a receptor for BAFF and is critical for the survival of bone marrow plasma cells. Paradoxically, BCMA deficiency exacerbates the formation of autoantibody-secreting plasma cells in spleens of lupus-prone mice and the reasons for this effect are not understood. Here we analyzed the phenotype, localization and function of neutrophils in spleens of healthy mice and congenic lupus-prone mice, and compared mice sufficient or deficient in BCMA expression. Neutrophils were found to be significantly increased in frequency and activation status in spleens of lupus-prone mice when BCMA was absent. Furthermore, neutrophils localized within T cell zones and enhanced CD4⁺ T cell proliferation and IFNγ production through the production of BAFF. Reduced BAFF and IFNγ serum levels, decreased frequencies of IFNγ-producing T cells, germinal center B cells, and autoantibody production after neutrophil depletion indicated the involvement of neutrophils in these autoimmune traits. Thus, we have identified a novel role for BCMA to control excess BAFF production in murine lupus through restraining the accumulation of BAFF-producing neutrophils. Our data suggests that devising therapeutic strategies to reduce neutrophils in autoimmunity may decrease BAFF levels and ameliorate disease.     

DeltaBAFF,an alternate splice isoform that regulates receptor binding and biopresentation of the B cell survival cytokine,BAFF

The tumor necrosis family member BAFF is limiting for the survival of follicular B lymphocytes, but excessive BAFF signaling can lead to autoimmunity, suggesting that its activity must be tightly regulated. We have identified a conserved alternate splice isoform of BAFF, called deltaBAFF, which lacks 57 nt encoding the A-A1 loop and is co-expressed with BAFF in many mouse and human myeloid cells. Mouse deltaBAFF appears on the plasma membrane, but unlike BAFF it is inefficiently released by proteolysis. DeltaBAFF can associate with BAFF in heteromultimers and diminish BAFF bioactivity and release. Thus, alternative splicing of the BAFF gene suppresses BAFF B cell stimulatory function in several ways, and deltaBAFF may promote other functions as well.     

Construction and characterization of a bi-functional EGFP/sBAFF fusion protein

A fusion between gene encoding fluoresce-enhanced green fluorescent protein variant (EGFP) and soluble domain of human B-cell-activating factor of the TNF family (sBAFF) was constructed and expressed in Escherichia coli. The EGFP/sBAFF had an apparent molecular weight of 45 kDa and was detected with anti-hsBAFF and anti-His(6) monoclonal antibodies. After being purified by immobilized metal affinity chromatography (IMAC), the fusion protein retained similar fluorescence spectra to those of EGFP. Biological activity assays showed the EGFP/sBAFF as well as sBAFF could co-stimulated human B lymphocyte proliferation in vitro. In addition, EGFP/sBAFF has shown specific binding to BAFF receptors positive-cells and the stained cells could be analyzed with flow cytometry. Thus, the fusion protein represents a readily obtainable source of biologically active sBAFF that may prove useful in further studies on BAFF and its receptors.     

Expression,purification and characterization of anti-BAFF antibody secreted from the yeast <Emphasis Type="Italic">Pichia pastoris</Emphasis>

B-Cell activating factor (BAFF) is critical for B cell survival and maturation; excessive expression of it corrupts B-cell tolerance and may lead to autoimmunity. The gene, scFv-Fc, coding for the antibody of BAFF was inserted into the eukaryotic expression vector, pPICZαA, and transformed into Pichia pastoris. A high-level expression strain was obtained using a ‘yeastern blotting’ method. The scFv-Fc antibody was purified and 56 mg was obtained from 1 l of culture supernatant. It retained high binding activity to both soluble BAFF and membrane-bound BAFF.     

活化T 细胞核因子在皮肤疾病发生与发展中的作用

活化T细胞核因子(nuclear factor of activated T cell,NFAT)作为细胞信号转导中的一类重要因子,最早被认为是一种能结合和上调T细胞中IL-2基因启动子的诱导性核因子,现发现它不仅在免疫系统中发挥功能,在肿瘤发生、发展中也起着关键性作用。近年来,越来越多的研究显示NFAT与人类皮肤疾病的发生、发展密切相关。在多种皮肤疾病患者真表皮成分中,NFAT异常表达,促进T细胞活化、表皮细胞增殖及自身免疫反应的形成,甚至促进肿瘤形成和浸润转移。本文旨在阐述研究发现的NFAT在皮肤疾病中发挥的重要作用,涉及T细胞活化、自身免疫反应形成、肿瘤形成及其浸润转移,以及NFAT在皮肤疾病中作用机制,预测这些研究结果对于皮肤病的治疗有着重要意义。     

BAFF inhibition: a new class of drugs for the treatment of autoimmunity

BAFF (BLyS) and APRIL are TNF-like cytokines that support survival and differentiation of B cells. Recent studies have discovered a role for BAFF in augmenting both innate and adaptive immune responses as well as in collaborating with other inflammatory cytokines to promote the activation and differentiation of effector immune cells. BAFF is an important pathogenic factor in lupus mouse models and BAFF inhibition successfully delays disease onset in these mice, although the responsiveness to BAFF inhibition varies among different strains. These results have led to the development of inhibitors targeting BAFF and APRIL in humans. An anti-BAFF antibody has shown significant but modest efficacy in two Phase III clinical trials for moderately active SLE and other inhibitors are being developed or at early stages of clinical testing.     

B cells flying solo

Systemic autoimmunity such as systemic lupus erythematosus (SLE) is associated with the loss of B-cell tolerance, B-cell dysregulation and autoantibody production. While some autoantibodies may contribute to the pathology seen with SLE, numerous studies have shown that dysregulation of T-cell function is another critical aspect driving disease. The positive results obtained in clinical trials using T-cell- or B-cell-specific treatments have suggested that cooperation between T and B cells probably underlies disease progression in many patients. A similar cooperative mechanism seemed to explain SLE developing in mice overexpressing the B-cell-activating factor from the tumor necrosis factor family (BAFF). However, surprisingly, T-cell-deficient BAFF transgenic (Tg) mice develop SLE similar to T-cell-sufficient BAFF Tg mice, and the disease was linked to innate activation of B cells and production of proinflammatory autoantibody isotypes. In conclusion, dysregulated innate activation of B cells alone can drive disease independently of T cells, and as such this aspect represents a new pathogenic mechanism in autoimmunity.     

sBAFF mutants induce neutralizing antibodies against BAFF

B cell activating factor belonging to the TNF family (BAFF) is a novel member of the tumor necrosis factor (TNF) ligand family and plays an important role in B lymphocyte maturation and survival. Overexpression of BAFF is closely involved in the pathogenesis and progression of many kinds of autoimmune disorders; therefore, BAFF has been considered as an ideal therapeutic target for these conditions. In this study, we generated several candidate immune inhibitors of human BAFF by conjugating foreign immunodominant T-helper cell (Th) epitopes to the N- or C-terminus of five BAFF mutants. The recombined proteins were successfully expressed in Escherichia coli (E. coli) and purified by Ni-NTA chromatography. BALB/c mice immunized with the recombinant proteins produced high levels of anti-BAFF antibodies, and their sera inhibited the lymphocyte proliferation-inducing activity of recombinant soluble BAFF and natural soluble BAFF. Moreover, antibodies cross-reactive with BAFF were detected in sera from hu-SCID mice immunized with the recombinant proteins. These results indicated that the recombinant BAFF mutants modified with Th epitopes could induce neutralizing antibodies against BAFF in vivo. This study may provide a valuable strategy for treating BAFF-associated autoimmune diseases.     

Binding of B‐cell maturation antigen to B‐cell activating factor induces survival of multiple myeloma cells by activating Akt and JNK signaling pathways

B‐cell maturation antigen (BCMA) is expressed on normal and malignant plasma cells and represents a potential target for therapeutic intervention. In this study, we characterized the mechanism underlying the protein kinase B (Akt) and c‐Jun N‐terminal kinase (JNK) pathways and BCMA interactions in regulating multiple myeloma (MM) cell survival. It was found that the expression levels of B cell‐activating factor (BAFF) and BCMA were increased in MM cells as compared with those in normal controls. The proliferation of U266 cells was induced by recombinant human BAFF (rhBAFF) and could also be decreased by BCMA siRNA. The expression of Bcl‐2 protein was up‐regulated, and Bax protein was down‐regulated after rhBAFF treatment, which could be reversed by BCMA siRNA. Similarly, the protein p‐JNK and p‐Akt were activated by rhBAFF and could be changed by BCMA siRNA. In addition, the BCMA mRNA and protein expression levels were decreased after treatment with Akt and JNK pathway inhibitors. These results suggest that Akt and JNK pathways are involved in the regulation of BCMA. A novel BAFF/BCMA signalling pathway in MM may be a new therapeutic target for MM. Copyright © 2016 John Wiley & Sons, Ltd.     

Global T cell dysregulation in non-autoimmune-prone mice promotes rapid development of BAFF-independent, systemic lupus erythematosus-like autoimmunity

In otherwise non-autoimmune-prone C57BL/6 (B6) mice rendered genetically deficient in CD152 (CTLA-4), polyclonal hypergammaglobulinemia with increased levels of systemic lupus erythematosus (SLE)-associated IgG autoantibodies, glomerular IgG and C3 deposition, and interstitial nephritis all developed by 3-5 wk of age. Remarkably, superimposing genetic deficiency of BAFF (B cell-activating factor belonging to the TNF family) onto CD152 deficiency did not substantially attenuate humoral autoimmunity and immunopathology in these mice, despite the resulting marked reduction in B-lineage cells. Although superimposing a BAFF transgene (resulting in constitutive BAFF overexpression) onto CD152-deficient mice did lead to increases in B-lineage cells and serum levels of certain SLE-associated IgG autoantibodies, renal immunopathology remained largely unaffected. Taken together, these results demonstrate that global T cell dysregulation, even in an otherwise non-autoimmune-prone host, can promote systemic humoral autoimmunity and immunopathology in a BAFF-independent manner. Moreover, supraphysiologic expression of BAFF in the setting of ongoing autoimmunity does not necessarily lead to greater immunopathology. These findings may help explain the limited clinical efficacy appreciated to date of BAFF antagonists in human SLE.     

B‐cell‐activating factor code and human cytomegalovirus infection in renal transplant recipients

The objective of the present study was to explore the correlation between the BAFF signal and HCMV‐TLR activation in RTx recipients complicated by HCMV. Peripheral blood (anticoagulated by EDTA‐Na₂) and urine of 113 RTx recipients were collected; healthy volunteers were controlled. Urine HCMV‐DNA was detected by real‐time PCR. Recipients were classified into a positive group (>10,000 copies/mL urine) and a negative group (<10,000 copies/mL urine). ELISA results showed that sBAFF, sera anti‐HCMV pp65 immunoglobulin (Ig)G antibody, and total IgG all significantly increased in recipients with positive HCMV‐DNA (>10,000 copies/mL urine) (P < 0.05) compared with negative recipients (<10,000 copies/mL urine). In the positive group, HCMV‐DNA copies and total IgG positively correlated with sBAFF (r = 0.988 and 0.625, respectively) (P < 0.05). Luminex assay results suggested that the incidence of anti‐HLA I and II and MICA antibody obviously increased in positive recipients. The expression level of BAFF and BAFF‐R increased in positive recipients. A total of 88 particular genes—involved in TLR signaling pathways, NF‐κB signaling pathways, and cytokine‐cytokine receptor signaling pathways—were detected in real‐time PCR chip assay. A total of 46 genes were differentially expressed greater than two‐fold, and the expression characteristic of BAFF‐R was concordant with FACS results. Our findings are that activation of HCMV would induce or enhance the activation of BAFF code in RTx recipients, which may independently or cooperatively participate in renal allograft injury and decrease the long‐term outcome of renal allografts.