BAFF-R Research Articles

Delayed onset of autoreactive antibody production and M2-skewed macrophages contribute to improved survival of TACI deficient MRL-Fas/Lpr mouse

Anti-B cell activating factor belonging to TNF-family (BAFF) antibody therapy is indicated for the treatment of patients with active systemic lupus erythematosus (SLE). We hypothesized that the BAFF receptor, transmembrane activator and calcium-modulator and cyclophilin interactor (TACI) may be responsible for the generation of antibody secreting plasma cells in SLE. To test this hypothesis, we generated TACI deficient MRL-Fas/Lpr (LPR-TACI−/−) mouse. TACI deficiency resulted in improved survival of MRL-Fas/Lpr mice and delayed production of anti-dsDNA and anti-SAM/RNP antibodies. There was also a delay in the onset of proteinuria and the accumulation of IgG and inflammatory macrophages (Mϕs) in the glomeruli of young LPR-TACI−/− mice compared to wild-type mice. Underscoring the role of TACI in influencing Mϕ phenotype, the transfer of Mϕs from 12-week-old LPR-TACI−/− mice to age-matched sick wild-type animals led to a decrease in proteinuria and improvement in kidney pathology. The fact that, in LPR-TACI−/− mouse a more pronounced delay was in IgM and IgG3 autoreactive antibody isotypes and the kinetics of follicular helper T (Tfh) cell-development was comparable between the littermates suggest a role for TACI in T cell-independent autoantibody production in MRL-Fas/Lpr mouse prior to the onset of T cell-dependent antibody production.

Environmental sensing by mature B cells is controlled by the transcription factors PU.1 and SpiB

Humoral immunity requires B cells to respond to multiple stimuli, including antigen, membrane and soluble ligands, and microbial products. Ets family transcription factors regulate many aspects of haematopoiesis, although their functions in humoral immunity are difficult to decipher as a result of redundancy between the family members. Here we show that mice lacking both PU.1 and SpiB in mature B cells do not generate germinal centers and high-affinity antibody after protein immunization. PU.1 and SpiB double-deficient B cells have a survival defect after engagement of CD40 or Toll-like receptors (TLR), despite paradoxically enhanced plasma cell differentiation. PU.1 and SpiB regulate the expression of many components of the B cell receptor signaling pathway and the receptors for CD40L, BAFF and TLR ligands. Thus, PU.1 and SpiB enable B cells to appropriately respond to environmental cues.

Profile of BAFF and its receptors’ expression in lupus nephritis is associated with pathological classes

Background/Objective B-cell activating factor (BAFF) plays an important role in the pathogenesis of systemic lupus erythematosus. However, the role of BAFF in lupus nephritis (LN) is not understood. Our aim was to evaluate the expression of BAFF and its three receptors in renal biopsy samples from patients with LN and investigate a relationship with pathological class. Methods We conducted a prospective descriptive study (2011-2014) on 52 kidney biopsy samples from patients with LN. Immunohistochemistry for BAFF, its receptors (transmembrane activator and calcium modulator and cyclophilin ligand interaction (TACI), protein maturation of B cells (BCMA), and BAFF-receptor (BAFF-R)), and CD20 expression was performed. Samples were scored according to the percentage of cells with positive expression. Results In class II LN, BAFF-R and TACI were not expressed, whereas BCMA and BAFF were lowly expressed in the interstitial inflammatory infiltrates. Proliferative class III/IV had elevated BAFF expression in the glomeruli, and TACI was expressed in interstitial inflammatory infiltrates and the glomeruli. Interestingly, the class IV cases with vasculopathy ( n = 4) had endothelial BAFF expression, which was not visible in thrombotic microangiopathy ( n = 4). Class V was characterized by low BAFF expression in interstitial inflammatory infiltrates and by BAFF, TACI, and BCMA expression in the glomeruli. BAFF expression was associated with inflammatory scores and CD20 positive infiltrates, mainly in class IV. Conclusions Expression patterns of BAFF and its receptors differ according to LN class. Our study provides evidence that BAFF could be used as a routine marker in LN biopsies and to determine which patients will benefit from anti-BAFF therapy.

Different IgM+ B cell subpopulations residing within the peritoneal cavity of vaccinated rainbow trout are differently regulated by BAFF

In teleost fish, IgM+ B cells are one of the main responders against inflammatory stimuli in the peritoneal cavity, as IgM+ B cells dominate the peritoneum after intraperitoneal stimulation, also increasing the levels of secreted IgM. BAFF, a cytokine known to play a major role in B cell biology, has been shown to be up-regulated along with its receptors in the peritoneum of rainbow trout upon antigenic exposure, however, the regulatory mechanisms underneath this response remain unclear. In this study, we have identified two different IgM+ B cell types residing in the peritoneal cavity of previously vaccinated rainbow trout (Oncorhynchus mykiss): IgD+IgMhiMHCIIhi cells, resembling naïve B cells, and IgD−IgMloMHCIIlo cells, resembling antibody-secreting cells. Based on their membrane IgM levels, these cell types were named IgMhi and IgMlo B cells, respectively. As each of these B cell populations showed a distinct expression pattern for the different BAFF receptors, we studied the effect of BAFF individually on each cell subset. Recombinant BAFF promoted the survival of IgMlo but not IgMhi B cells in vitro, resulting in increased levels of IgM-secreting cells. In contrast, BAFF increased the levels of membrane MHC II only on IgMhi B cells, suggesting different functions on these B cell subsets. Moreover, we also showed that peritoneal IgMhi B cells expressed BAFF at levels comparable to those seen on myeloid cells. These results point to BAFF as a main regulator of B cell homeostasis in the peritoneal cavity, suggesting that this cytokine can trigger different signals on different peritoneal B cell subsets in a specific manner.

B cell activating factor (BAFF) and BAFF receptors: fakes and facts.

Analysis of B cell activating factor (BAFF) receptors before and after B cell depletion therapy (BCDT) might offer a clue to the understanding of whether some B cell subsets may represent useful biomarkers of biological and clinical responses. Among the BAFF receptors in a cohort of rheumatoid arthritis (RA) patients, the AA have shown, by fluorescence activated cell sorter (FACS) analysis of median fluorescence intensity (MFI), that transmembrane activator and calcium-modulating cyclophilin ligand interactor (TACI) and B cell maturation antigen (BCMA) do not change, whereas the most important, BAFF receptor 3 (BR3), appears to be decreased before as well as after BCDT in all B cell subsets but not in plasmablasts, the most important subset, depleted by BCDT.

Effects of B cell activating factor in pathogenesis of multiple myeloma

Multiple myeloma (MM) is a kind of malignant proliferative disease of plasma cell. The malignant proliferations of MM cells heavily depend on bone marrow microenvironment. B cell activating factor (BAFF), as an important component of bone marrow microenvironment, plays an important role in pathogenesis of MM. MM cells express a variety of B cell activating factor receptor (BAFF-R), and BAFF and BAFF-R combine to activate nuclear factor kappa B signaling pathway, which is one of the most important signal transduction pathways in pathogenesis of MM. Compared with healthy individuals, the levels of BAFF in patients with MM are significantly increased. Therefore, the related researches on BAFF have great significance in treatment of MM. The author summarized the tumor promoting effect of BAFF in MM. Key words: Multiple myeloma; B-cell activating factor; B-cell activation factor receptor; Tumor necrosis factors

Microglia-mediated BAFF–BAFFR ligation promotes neuronal survival in brain ischemia injury

The innate immune responses of brain to vascular occlusion are primarily orchestrated by activated microglia. However, the roles of microglia in inflammatory responses to brain ischemic injuries are controversial. Here, we report a new mechanism by which microglia confer protective effects on ischemic neuronal cells. We found that under ischemic condition, the B-cell-activating factor (BAFF) was vastly upregulated in microglia and this upregulation could at least be attributed to JAK-STAT signaling pathway activated by IFN-γ and IL-10, which were spatio-temporally enriched in I/R-injured brain as well. Meanwhile, the expression of BAFFR, one member of BAFF receptors, was also upregulated on neurons after I/R injury. More importantly, recombinant BAFF treatment not only promoted neuronal survival under ischemic stresses in vitro but also attenuated infarct volume and neural deficit caused by middle cerebral artery occlusion (MCAO) in vivo. Furthermore, blocking BAFF–BAFFR ligation with TACI-Ig abrogated these therapeutic benefits. Taken together, these results indicate that the BAFF–BAFFR ligation bridged between microglia and neurons could play a critical neuroprotective role in I/R injury. Thus, augmenting BAFF–BAFFR signaling might represent a potential target for clinical stroke therapy.

The Role of BAFF System Molecules in Host Response to Pathogens.

The two ligands B cell-activating factor of the tumor necrosis factor family (BAFF) and a proliferation-inducing ligand (APRIL) and the three receptors BAFF receptor (BAFF-R), transmembrane activator and calcium-modulating cyclophilin ligand interactor (TACI), and B cell maturation antigen (BCMA) are members of the "BAFF system molecules." BAFF system molecules are primarily involved in B cell homeostasis. The relevance of BAFF system molecules in host responses to microbial assaults has been investigated in clinical studies and in mice deficient for each of these molecules. Many microbial products modulate the expression of these molecules. Data from clinical studies suggest a correlation between increased expression levels of BAFF system molecules and elevated B cell responses. Depending on the pathogen, heightened B cell responses may strengthen the host response or promote susceptibility. Whereas pathogen-mediated increases in the expression levels of the ligands and/or the receptors appear to promote microbial clearance, certain pathogens have evolved to ablate B cell responses by suppressing the expression of TACI and/or BAFF-R on B cells. Other than its well-established role in B cell responses, the TACI-mediated activation of macrophages is also implicated in resistance to intracellular pathogens. An improved understanding of the role that BAFF system molecules play in infection may assist in devising novel strategies for vaccine development.

SYK inhibition thwarts the BAFF - B-cell receptor crosstalk and thereby antagonizes Mcl-1 in chronic lymphocytic leukemia.

Although small molecule inhibitors of B-cell receptor-associated kinases have revolutionized therapy in chronic lymphocytic leukemia (CLL), responses are incomplete. Pro-survival signaling emanating from the microenvironment may foster therapeutic resistance of the malignant B cells resident in the protective lymphoid niches. B-cell activating factor (BAFF) is critical to the survival of both healthy and neoplastic B cells. However, the pro-survival pathways triggered by BAFF have not been fully characterized. Here we show that BAFF elicited resistance to spontaneous and drug-induced apoptosis in stromal co-cultures, induced activation of both canonical and non-canonical NFκB signaling pathways, and triggered B-cell receptor signaling in CLL cells, independently of IGHV mutational status. SYK, a proximal kinase in the B-cell receptor signaling cascade, acted via STAT3 to bolster transcription of the anti-apoptotic protein Mcl-1, thereby contributing to apoptosis resistance in BAFF-stimulated cells. SYK inhibitor entospletinib downregulated Mcl-1, abrogating BAFF-mediated cell survival. BAFF-B-cell receptor crosstalk in neoplastic B cells was mediated by SYK interaction with TRAF2/TRAF3 complex. Thus, SYK inhibition is a promising therapeutic strategy uniquely poised to antagonize crosstalk between BAFF and B-cell receptor, thereby disrupting the pro-survival microenvironment signaling in chronic lymphocytic leukemia.

Effects of B cells activating factor on growth characteristics of mouse renal tubular epithelial cells

Objective To investigate the expression of B cell activating factor (BAFF) and BAFF receptor (BAFF-R) on primary mouse renal tubular epithelial cells (RTECs), and the effect on growth characteristics of RTECs. Methods Primary mouse RTECs were isolated by enzyme digestion method, and cultured in the conditioned medium. After stimulated by 500 U/ml Interferon-γ (IFN-γ) for 48 h, the expression of BAFF and BAFF-R on RTECs were detected by Flow Cytometry (FCM). After treated with recombinant mouse BAFF and/or blockade B cell activating factor receptor-Fc fusion protein (BAFF-R-Fc) for 48 h, the transport ability of fluorescein sodium and cytokeratin-18 (CK-18) expression of RTECs were detected, respectively; The proliferation ability and the apoptosis rates of RTECs were tested by 3- (4, 5-dimenthylthiazol-2-yl)-5- (3-carboxymethoxyphenyl)-2- (4-sulfophenyl)-2H-tetrazolium (MTS) and FCM method, respectively; Data were analyzed by SPSS 17.0, and P<0.05 was considered to be statistically significant. Results BAFF-R expression on RTECs in the IFN-γ treated group significantly up-regulated, compared with control group (4 166.250±913.914 vs. 3 602.750±875.584, t=4.124, P=0.026). Fluorescein sodium transport experiment showed the average absorbance of BAFF stimulation group was significantly lower than BAFF-R-Fc+ BAFF group (0.011±0.003 vs. 0.020±0.007, t=-3.437, P=0.041), and control group (0.011±0.003 vs. 0.016±0.006, t=-3.572, P=0.038); Immunofluorescence results showed the average absorbance of BAFF stimulation group was significantly lower than that of BAFF-R-Fc+ BAFF group (0.032±0.005 vs. 0.043±0.007, t=-8.006, P=0.015), and control group (0.032±0.005 vs. 0.041±0.008, t=-4.603, P=0.044); Cell proliferation assay results showed that, A value of 5 ng/ml and 20 ng/ml BAFF group were significantly higher than that of control group (1.532±0.058 vs. 1.473±0.045; 1.509±0.056 vs. 1.473±0.045, t=5.636, P=0.030; t=5.765, P=0.029, respectively), and A value of 5 ng/ml BAFF group were significantly higher than that of BAFF-R-Fc+ BAFF group (1.532±0.058 vs. 1.477±0.050, t=5.085, P=0.037); Apoptosis test results indicated that the apoptosis rate of BAFF-treated group was significantly lower than that of BAFF-R-Fc+ BAFF group [(39.850±8.544)% vs. (42.950±8.330)%, t=-3.399, P=0.019], and control group [(39.850±8.544)% vs. (44.467±7.642)%, t=-3.020, P=0.029]. Conclusion BAFF signaling could promote the proliferation ability of RTECs, but down-regulate the epithelial cell characteristics and Ion transport ability of RTECs. Key words: Renal tubular epithelial cell; B cell activating factor; Cytokeratin-18; Ion transport; Proliferation

Recurrent respiratory tract infections (RRTI) in the elderly: A late onset mild immunodeficiency?

Elderly with late-onset recurrent respiratory tract infections (RRTI) often have specific anti-polysaccharide antibody deficiency (SPAD). We hypothesized that late-onset RRTI is caused by mild immunodeficiencies, such as SPAD, that remain hidden through adult life. We analyzed seventeen elderly RRTI patients and matched controls. We determined lymphocyte subsets, expression of BAFF receptors, serum immunoglobulins, complement pathways, Pneumovax-23 vaccination response and genetic variations in BAFFR and MBL2. Twelve patients (71%) and ten controls (59%) had SPAD. IgA was lower in patients than in controls, but other parameters did not differ. However, a high percentage of both patients (53%) and controls (65%) were MBL deficient, much more than in the general population. Often, MBL2 secretor genotypes did not match functional deficiency, suggesting that functional MBL deficiency can be an acquired condition. In conclusion, we found SPAD and MBL deficiency in many elderly, and conjecture that at least the latter arises with age.

The lymphomagenic molecule LMP1 sequesters TRAF3 to induce enhanced B cell survival.

Abstract The human TRAF3 gene is frequently mutated in multiple myeloma and lymphoma. TRAF3 restrains homeostatic B cell survival. B cell TRAF3 deficiency promotes enhanced viability and over-expression of the anti-apoptotic molecules NIK, Mcl1 and Pim2, enhanced nuclear CREB, and increased pSTAT3 in response to IL6 signaling. We assessed TRAF3 protein expression in human lymphoma samples. The number of TRAF3low DLBCL was higher than predicted based on genetic loss, so we speculated that cellular TRAF3 can be depleted through other means. The oncogenic Epstein Barr virus protein LMP1 binds TRAF3 with much higher avidity than do CD40 or BAFF receptors, so we hypothesized that LMP1-sequesters TRAF3, causing functional depletion. We found evidence of induction of survival pathways in TRAF3 sufficient B cells expressing LMP1 consistent with those in B cells genetically lacking TRAF3. B lymphoma cell lines stably transfected with inducible LMP1 were stimulated via CD40 or BAFFR. TRAF3 binding was studied via CD40/BAFFR immunoprecipitation and Western blotting. We also examined levels of cellular NIK, and used confocal fluorescence microscopy to assess nuclear CREB expression. We found LMP1 expression sequesters cellular and nuclear TRAF3, decreasing its availability to CD40 and BAFFR, and increases survival-promoting NIK, CREB and pSTAT3. LMP1 mutated at the major TRAF binding site only marginally induced TRAF3 sequestration and NIK. Thus, B cell LMP1 expression can enhance survival by functionally reducing TRAF3 availability.

Abstract 484: Multimerization of BAFF Regulates B Cell Function and Growth of Aortic Aneurysms

B cell activating factor (BAFF) regulates differentiation and survival of B cells by binding to the surface receptors BAFF receptor (BR3), transmembrane activator and CAML interactor (TACI) and B cell maturation antigen (BCMA). During differentiation, intracellular metabolic reprogramming is crucial, such as, naïve B cells are metabolically quiescent, whereas, antibody producing plasma cells are metabolically active. We have reported that depletion of B cells protects mice from abdominal aortic aneurysm (AA), however it is not clear how B cells promote AA growth. BAFF exists as a 3mer (binds only to BR3) or as a 60mer (binds to BR3, TACI and BCMA). Therefore, we hypothesize that BAFF multimerization regulates the immune and metabolic phenotype of B cells by binding to BAFF receptors and modulate AA growth. Immunohistology was performed on AA tissues collected from patients undergoing open AA repair. Experimental AA was induced by elastase perfusion of abdominal aorta or angiotensin II infusion (1000 ng/kg/min) method in 8 weeks old male C57BL/6 or apolipoprotein E knockout mice, respectively. Western blotting, flow cytometry and Seahorse extracellular flux assays were used to determine immune and metabolic changes in B cells in response to recombinant BAFF 3mer and 60mer. BR3+ B cells were detected in the milieu of BAFF in human AAs. Mouse AAs demonstrated significant infiltration (&gt;50/section) of CD138+ plasma B cells, but few (4-10/section) CD20+ B cells. In vitro, BAFF 3mer induced canonical NF-kB, whereas, 60mer induced both canonical and non-canonical NF-kB signaling. Moreover, the 3mer significantly decreased mitochondrial density, oxygen consumption rate, and surface expression of IgD and IgM indicating a metabolically quiescent state of B cells. However, these parameters were significantly increased by the 60mer similar to plasma cells. Anti-BR3 IgG1, but not a control IgG1 antibody decreased BAFF 60mer-induced oxygen consumption rate by 50%. In a pilot study (n=10/group), anti-BR3 IgG1, but not the control IgG1 aggravated angiotensin II-induced AA growth. Altogether, our results suggest that BAFF 3mer and 60mer oppositely regulate immune and metabolic phenotype of B cells and inhibition of BAFF-BR3 signaling is detrimental for AA growth.

TACI-deficient macrophages alleviate metabolic disease symptoms in obese mice

Abstract TACI (transmembrane activator and calcium-modulator and cyclophilin ligand interactor) is one of receptors for the TNF superfamily cytokines BAFF (B cell activating factor) and APRIL (A Proliferation Inducing Ligand). In this study, we investigated the role of TACI in high fat diet induced obesity and metabolic disease. Compared to WT mice, TACI KO mice exhibited less weight gain, decreased body fat, enhanced glucose tolerance and insulin sensitivity. Improved metabolic changes in TACI KO mice were accompanied by significantly less accumulation of CD8+ T cells and F4/80+CD11c+ inflammatory macrophages in visceral fat pad. In addition, TACI KO mouse adipose tissue contained elevated numbers of ILC2, eosinophils and M2 macrophages. Underscoring the protective phenotype of M2-skewed macrophages, the transfer of TACI KO macrophages into obese WT mouse significantly improved insulin sensitivity and glucose tolerance in WT mouse. Interestingly, adoptively transferred TACI KO macrophages into WT mice also increased numbers of the host M2 macrophages and eosinophils in the adipose tissue. We identified IL-10 secreted by TACI KO macrophages was majorly responsible for the improved insulin sensitivity because not only TACI KO macrophage culture media contained high levels of IL-10 but also an IL-10 blocking antibody abolished the enhancement of insulin signaling provided by TACI KO macrophage culture media. These findings indicate that macrophage TACI mediated inflammatory signals promote obesity induced metabolic changes. Consequently, TACI blocking reagents may offer therapeutic benefits to obese patients suffering from metabolic complications.

Dose dependent effect of BAFF receptor specific mAb-siRNA conjugate in experimental myasthenia

Abstract We investigated potential therapeutic effect of a conjugate of BAFF receptor specific- monoclonal antibody and short interference RNA in a mouse model of myasthenia gravis (EAMG). We found that at high dose, conjugate treatment caused significant accumulation of Fas expressing CD19+/ B220+ cells and increased type 1 interferon in lymph nodes. Low dose did not induce FAS expression but caused marked BAFF receptor deficiency in lymph nodes that was further associated with improved MG symptoms. Conjugate treatment, however, did not reduce the levels of autoantibody. Our findings, thus, reveal a previously undocumented, dose dependent, immunomodulatory distant effect resulting from BAFF receptor specific mAb-siRNA conjugate treatment in an in vivo model of autoimmune disease.

Inhibition of BAFF binding to its receptor, BR3, by low molecular weight compounds results in suppression of activation of monocytes and B cells in vitro and in vivo model of autoimmune diseases.

Abstract Background and Purpose We have demonstrated that the elevated expression of BAFF receptor (BR3) on monocytes is involved in the pathogenesis of primary Sjogren’s syndrome and BR3 is a therapeutic target to treat pSS. In our previous study, we have discovered two pyrrolopryimidine derivatives, BIK12 and BIK13, which inhibit binding of BAFF to BR3, using our original high-throughput screening system. In this study, we investigated inhibitory effects of these compounds on BAFF signaling pathways in monocytes and B cells in vitro. In addition, we analyzed the effects of the compounds on serum level of an anti-dsDNA antibody in autoimmune disease model mice. Methods Peripheral monocytes were stimulated with soluble BAFF (sBAFF) and cultured in vitro with or without peripheral B cells in the presence of BIK-12 or BIK-13. IL-6 production by monocytes and IgG production by B cells were measured by ELISA. MRL/lpr and NZBWF1 mice were treated with these compounds three times a week at a dose of 1.0 or 0.2 mg/kg for 6 months. The titer of an anti-ds DNA antibody was measured by ELISA. Results and Discussion sBAFF-induced IL-6 production by peripheral monocytes and IgG production by B cells co-cultured with sBAFF-stimulated peripheral monocytes were significantly suppressed by BIK12 and BIK13 in a dose dependent manner. Interestingly, the titer of an anti-dsDNA antibody in both MRL/lpr and NZBWF1 mice received BIK13 was significantly lower than control mice after 16 weeks’ treatment, indicating that the compound was also efficacious in vivo.

Human Plasmacytoid Dendritic Cells Display and Shed B Cell Maturation Antigen upon TLR Engagement.

The BAFF-APRIL system is best known for its control of B cell homeostasis, and it is a target of therapeutic intervention in autoimmune diseases and lymphoma. By analyzing the expression of the three receptors of this system, B cell maturation Ag (BCMA), transmembrane activator and CAML interactor, and BAFF receptor, in sorted human immune cell subsets, we found that BCMA was transcribed in plasmacytoid dendritic cells (pDCs) in both blood and lymphoid tissue. Circulating human pDCs contained BCMA protein without displaying it on the cell surface. After engagement of TLR7/8 or TLR9, BCMA was detected also on the cell surface of pDCs. The display of BCMA on the surface of human pDCs was accompanied by release of soluble BCMA (sBCMA); inhibition of γ-secretase enhanced surface expression of BCMA and reduced the release of sBCMA by pDCs. In contrast with human pDCs, murine pDCs did not express BCMA, not even after TLR9 activation. In this study, we extend the spectrum of BCMA expression to human pDCs. sBCMA derived from pDCs might determine local availability of its high-affinity ligand APRIL, because sBCMA has been shown to function as an APRIL-specific decoy. Further, therapeutic trials targeting BCMA in patients with multiple myeloma should consider possible effects on pDCs.

Alteration of B cell subsets and the receptor for B cell activating factor (BAFF) in paediatric patients with type 1 diabetes

BackgroundLately, mounting evidence has shown that B cells play an important role in the pathogenesis of type 1 diabetes (T1D). Here, we present alterations in B cell subsets including BAFF receptor (BAFFR) expression in cohorts of patients with type 1 diabetes (T1D) and their relatives. Patients and methodsB cells were studied in 438 patients with T1D (158 at disease onset and 280 with long-term disease), 136 first-degree relatives and 53 healthy controls. The B cell panel included transitional, naïve, MZ-like, switched memory B cells and plasmablasts. We also measured serum BAFF levels as well as BAFFR expression on both B and T cells. Moreover, the effect of BAFF on T and B lymphocytes was analysed in vitro. ResultsWe observed a significant decrease in the proportion of transitional B cells in the patients with T1D, accompanied by an increased proportion of plasmablasts, especially in recent-onset patients and their relatives. While the BAFF serum levels did not differ in the patients with T1D, BAFFR-expressing B and especially T cell numbers were reduced in the T1D cohort, with the exception of patients with recent-onset disease who exhibited a significant increase in the number of BAFFR-expressing T cells. T cell activation and B cell proliferation were more pronounced after activation with BAFF in the T1D cohort compared to controls. ConclusionThe B cell panel in patients with T1D is characterized by significantly reduced populations of B cells in their early stages of development with a shift towards plasma cells. The dynamics of BAFFR-expressing B and T cells and the more pronounced responsiveness of the T1D T cells to BAFF point to the role of BAFF and T and B cell cooperation in the development of T1D.

Up-regulated BAFF and BAFF receptor expression in patients with intractable temporal lobe epilepsy and a pilocarpine-induced epilepsy rat model

PurposeSome studies have suggested that BAFF and BAFFR are highly expressed in the central nervous system (CNS) and participate in inflammatory and immune associated diseases. However, whether BAFF and BAFFR are involved in the pathogenesis of epilepsy remains unknown. This study aimed to investigate the expression of BAFF and BAFFR proteins in the brains of patients with temporal lobe epilepsy (TLE) and in a pilocarpine-induced rat model of TLE to identify possible roles of the BAFF–BAFFR signaling pathway in epileptogenesis. MethodsReal-time quantitative polymerase chain reaction (RT-qPCR), western blot, immunohistochemistry, and double-immunofluorescence were performed in this study. ResultsThe results showed that BAFF and BAFFR expression levels were markedly up-regulated in intractable TLE patients and TLE rats. Moreover, BAFF and BAFFR proteins mainly highly expressed in the membranes and cytoplasms of the dendritic marker MAP2 in the cortex and hippocampus. ConclusionTherefore, the significant increased in BAFF and BAFFR protein expression in both TLE patients and rats suggest that BAFF and BAFFR may play important roles in regulating the pathogenesis of epilepsy.

Characterization of BAFF and APRIL subfamily receptors in rainbow trout (Oncorhynchus mykiss). Potential role of the BAFF / APRIL axis in the pathogenesis of proliferative kidney disease.

Proliferative kidney disease (PKD) is a parasitic infection of salmonid fish characterized by hyper-secretion of immunoglobulins in response to the presence of the myxozoan parasite, Tetracapsuloides bryosalmonae. In this context, we hypothesized that the BAFF/APRIL axis, known to play a major role in B cell differentiation and survival in mammals, could be affected by the parasite and consequently be involved in the apparent shift in normal B cell activity. To regulate B cell activity, BAFF and APRIL bind to transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) and B cell maturation antigen (BCMA), whereas BAFF also binds to BAFF receptor (BAFF-R). In teleost fish, although some BAFF and APRIL sequences have been reported, their receptors have not been identified. Thus, as a first step in the current work, we have identified homologues to mammalian TACI, BCMA and BAFF-R in rainbow trout (Oncorhynchus mykiss), that constitute the first report of BAFF and APRIL receptor sequences in fish. Subsequently we studied the transcriptional modulation of BAFF, APRIL, and the fish-specific related cytokine, BALM and their putative receptors in fish naturally exposed to T. bryosalmonae. Finally, to gain further insights on the functional role that these cytokines play during the course of PKD, we have studied their effect on the survival of kidney IgM+ B cells and on immunoglobulin transcription. Our results support the premise that the BAFF / APRIL axis could play an important role during PKD, which may open the possibility of new therapeutic treatments against the disease.