Increased vitreous levels of B cell activation factor (BAFF) and soluble interleukin-6 receptor in patients with macular edema due to uveitis related to Behçet's disease and sarcoidosis.

PURPOSE: Uveitis accounts for 10-15% of all cases of blindness in the developed world. Uveitic macular edema (UME) is a primary cause of permanent visual impairment in patients with uveitis. Because proinflammatory mediators elicit inflammation and lead to UME, we determined the profiles of proinflammatory mediators associated with complications, such as ME, in the vitreous humor of patients with panuveitis related to Behçet's disease (BD) and sarcoidosis. METHODS: In this retrospective study, we enrolled 21 patients with uveitis, including 6 with BD and 15 with sarcoidosis, and 15 patients with idiopathic epiretinal membrane (iERM) at the Department of Ophthalmology, Kyushu University Hospital, between January 2008 and April 2016. Vitreous concentrations of 32 proinflammatory mediators, including cytokines and soluble receptors of tumor necrosis factor (TNF) and interleukin (IL)-6 families, were assessed using a bead-based multiplex assay and their association with clinical data was examined. RESULTS: The levels of proinflammatory mediators, including a proliferation-inducing ligand (APRIL), B cell activating factor belonging to the TNF family (BAFF), soluble cluster of differentiation 30 (sCD30), soluble TNF receptor-1 (sTNFR1), sTNFR2, TNF-α, IL-6, and soluble IL-6 receptor-α (sIL-6Rα), were significantly higher in patients with uveitis. With regard to clinical parameters in patients with uveitis, vitreous levels of BAFF and sIL-6Rα were prominently elevated in patients with UME compared to in those without UME (P < 0.01, respectively). CONCLUSIONS: Our results suggest that elevated vitreous levels of BAFF and sIL-6Rα are associated with the pathogenesis of UME in patients with panuveitis related to BD and sarcoidosis.

Neutrophil Expression of T and B Immunomodulatory Molecules in HIV Infection.

Objective: Evaluate the expression of B and T cell immunomodulatory molecules in polymorphonuclear neutrophils (PMN) in HIV-infected patients. Methods: HIV load, bacterial translocation and neutrophils' expression of T [programmed death ligand, interleukin-10+, arginase 1+] and B [BAFF, APRIL] molecules were analyzed in different cohorts and time points: a control group of 25 healthy individuals and two groups of HIV-infected patients. Group 1 of patients included 35 untreated patients, studied at baseline and after antiretroviral therapy (ART). Group 2 was composed of 25 patients with undetectable viral load after a median of 101 months of ART prior to inclusion in the study. Results: Compared with the control group, group 1 patients showed increased bacterial translocation and their PMN had a significantly higher expression of T and B-cell immunomodulatory molecules, both at baseline and after 12 months of ART. Group 2 patients showed reduced bacterial translocation levels when compared with group 1 patients after 12 months of treatment. PMN expression of B-cell modulators was similar between group 2 patients and healthy controls, although the expression of T-cell modulators remained increased. Conclusion: In HIV-infected patients, the expression of B-cell stimulatory and T-cell suppressive molecules by neutrophils was increased at baseline and after a limited time of therapy. After a prolonged period of ART, only PMNs expression of T-cell immunosuppressive molecules remained elevated.

Bacterial Lipoproteins Induce BAFF Production via TLR2/MyD88/JNK Signaling Pathways in Dendritic Cells.

B-cell activating factor (BAFF) plays a crucial role in survival, differentiation, and antibody secretion of B cells. Microbial products with B-cell mitogenic properties can indirectly promote expansion and activation of B cells by stimulating accessory cells, such as dendritic cells (DCs), to induce BAFF. Although bacterial lipoproteins are potent B-cell mitogen like lipopolysaccharides (LPSs), it is uncertain whether they can stimulate DCs to induce BAFF expression. Here, we evaluated the effect of bacterial lipoproteins on BAFF expression in mouse bone marrow-derived DCs. Lipoprotein-deficient Staphylococcus aureus mutant induced relatively low expression level of membrane-bound BAFF (mBAFF) and the mRNA compared with its wild-type strain, implying that bacterial lipoproteins can positively regulate BAFF induction. The synthetic lipopeptides Pam2CSK4 and Pam3CSK4, which mimic bacterial lipoproteins, dose-dependently induced BAFF expression, and their BAFF-inducing capacities were comparable to those of LPS in DCs. Induction of BAFF by the lipopeptide was higher than the induction by other microbe-associated molecular patterns, including peptidoglycan, flagellin, zymosan, lipoteichoic acid, and poly(I:C). Pam3CSK4 induced both mBAFF and soluble BAFF expression in a dose- and time-dependent manner. BAFF expression by Pam3CSK4 was completely absent in DCs from TLR2- or MyD88-deficient mice. Among various MAP kinase inhibitors, only JNK inhibitors blocked Pam3CSK4-induced BAFF mRNA expression, while inhibitors blocking ERK or p38 kinase had no such effect. Furthermore, Pam3CSK4 increased the DNA-binding activities of NF-κB and Sp1, but not that of C/EBP. Pam3CSK4-induced BAFF promoter activity via TLR2/1 was blocked by NF-κB or Sp1 inhibitor. Collectively, these results suggest that bacterial lipoproteins induce expression of BAFF through TLR2/MyD88/JNK signaling pathways leading to NF-κB and Sp1 activation in DCs, and BAFF derived from bacterial lipoprotein-stimulated DCs induces B-cell proliferation.

B-Cell Activating Factor Secreted by Neutrophils Is a Critical Player in Lung Inflammation to Cigarette Smoke Exposure.

Cigarette smoke (CS) is the major cause of chronic lung injuries, such as chronic obstructive pulmonary disease (COPD). In patients with severe COPD, tertiary lymphoid follicles containing B lymphocytes and B cell-activating factor (BAFF) overexpression are associated with disease severity. In addition, BAFF promotes adaptive immunity in smokers and mice chronically exposed to CS. However, the role of BAFF in the early phase of innate immunity has never been investigated. We acutely exposed C57BL/6J mice to CS and show early BAFF expression in the bronchoalveolar space and lung tissue that correlates to airway neutrophil and macrophage influx. Immunostaining analysis revealed that neutrophils are the major source of BAFF. We confirmed in vitro that neutrophils secrete BAFF in response to cigarette smoke extract (CSE) stimulation. Antibody-mediated neutrophil depletion significantly dampens lung inflammation to CS exposure but only partially decreases BAFF expression in lung tissue and bronchoalveolar space suggesting additional sources of BAFF. Importantly, BAFF deficient mice displayed decreased airway neutrophil recruiting chemokines and neutrophil influx while the addition of exogenous BAFF significantly enhanced this CS-induced neutrophilic inflammation. This demonstrates that BAFF is a key proinflammatory cytokine and that innate immune cells in particular neutrophils, are an unconsidered source of BAFF in early stages of CS-induced innate immunity.

The effects of BAFF on T lymphocytes in chronic obstructive pulmonary disease.

BACKGROUND: It has been reported that B cell activating factor belonging to the tumor necrosis factor family (BAFF) expression is increased in chronic obstructive pulmonary disease (COPD). However its role in this chronic inflammatory disease is not fully understood. Previous studies have suggested that BAFF also affects T cell function. We therefore investigated the effects of BAFF on T lymphocytes in COPD. METHODS: BAFF was detected in the cells of sputum and the plasma. Peripheral blood mononuclear cells (PBMCs) were isolated from COPD patients and treated with BAFF or BAFF plus BR3-Fc (BAFF antagonist). The apoptosis of CD4+ cells and CD8+ cells was analyzed by flow cytometry. CD4+ cells and CD8+ cells were isolated from peripheral blood of COPD patients respectively and treated with BAFF or BAFF plus BR3-Fc. Interferon-γ (IFN-γ) and interleukin-4 (IL-4) were detected in the CD4+ cells, and perforin and granzyme B were detected in the CD8+ cells. RESULTS: BAFF expression was increased in the cells of sputum and the plasma from COPD patients compared with control subjects. The plasma BAFF levels were inversely correlated with FEV1 percentage of predicted in patients with COPD. BAFF did not significantly alter the apoptosis of CD4+ cells, however it significantly inhibited the apoptosis of CD8+ cells from COPD patients. BAFF increased IFN-γ expression in the CD4+ cells from COPD patients, while it did not significantly alter the expresson of IL-4 in these cells. BAFF increased the expression of perforin and granzyme B in the CD8+ cells from COPD patients. CONCLUSIONS: Our findings indicate that BAFF may be involved in the inflammatory response in COPD via affecting T lymphocytes, suggesting a possible role of BAFF in the pathogenesis of COPD.

High BAFF expression associated with active disease in systemic lupus erythematosus and relationship with rs9514828C>T polymorphism in TNFSF13B gene.

B cell-activating factor (BAFF) promotes the survival, proliferation and maturation of B lymphocytes, which are key elements in the pathogenesis of systemic lupus erythematosus (SLE). This cytokine is encoded on TNFSF13B gene, and diverse single-nucleotide polymorphisms have been associated with susceptibility in different autoimmune disorders. In this study, the relationship of TNFSF13B gene rs9514827T>C, rs1041567T>A and rs9514828C>T polymorphisms, mRNA expression and soluble BAFF levels was investigated in 175 SLE patients and 208 healthy controls (HC). The TNFSF13B polymorphisms were evaluated by PCR-RFLP technique. The TNFSF13B gene expression was quantified through the RT-PCR assays. The soluble BAFF (sBAFF) levels were measured with ELISA test. There were no differences in genotype and allele frequencies for the three TNFSF13B polymorphisms, between SLE patients and HC. SLE patients showed 3.15-fold more TNFSF13B gene expression than HC. The patients who displayed most mRNA expression were those with active disease and the carriers of rs9514828 T variant allele. The sBAFF serum levels were higher in SLE patients compared to HC (2.083 vs. 0.742 ng/mL, p < 0.001). The SLE patients with active disease showed the higher sBAFF serum levels (2.403 ng/mL), mainly patients with lupus nephritis and hematological manifestations. In addition, a correlation of sBAFF with disease activity was found (r = 0.32, p < 0.001). In conclusion, the TNFSF13B gene polymorphisms were not found to be associated with SLE susceptibility in Mexican mestizos. Nevertheless, rs9514828C>T polymorphism seems to increase TNFSF13B gene expression. High BAFF expression is related to active disease, renal and hematological involvement; therefore, it could be considered as follow-up biomarker in SLE patients.

JAK-1 Inhibition Suppresses Interferon-Induced BAFF Production in Human Salivary Gland: Potential Therapeutic Strategy for Primary Sjögren's Syndrome.

OBJECTIVE: To examine whether a JAK inhibitor regulates functional responses of human salivary gland epithelial cells (SGECs) and disease parameters in an animal model of Sjögren's syndrome (SS). METHODS: Common differentially expressed genes (DEGs) were analyzed among peripheral blood mononuclear cells from patients with primary SS and other data sets, using blood and SG tissue. Validation of expression in SGs was analyzed by focus score. Inhibition of messenger RNA expression of DEGs and BAFF by filgotinib was analyzed using reverse transcription-polymerase chain reaction in primary SGECs. SG organoid cultures were used to determine the association between DEGs and BAFF via knockdown using small interfering RNAs or to determine regulation of BAFF by JAK inhibitor. Filgotinib (1.5 mg/kg) was intraperitoneally injected into 8-week-old NOD/ShiLtJ mice 3 times per week to analyze manifestations of disease. Finally, STAT signaling was assessed in human and mouse SGECs. RESULTS: Expression of the DEGs IFNG and BAFF increased in SGs from patients with primary SS, as assessed by focus score. There was a significant correlation between IFIT2 and BAFF expression. JAK inhibitor suppressed interferon (IFN)-induced transcription of DEGs and BAFF in human primary SGECs. Knockdown of DEGs or inhibition of JAK caused reduced secretion of BAFF in human SG organoid cultures. In addition, filgotinib-treated mice exhibited increased salivary flow rates and marked reductions in lymphocytic infiltration of SGs. JAK inhibitor regulated IFNα- and IFNγ-induced pSTAT-1Y701 , pSTAT-3Y705 , and protein inhibitor of activated STAT-3 (PIAS-3) in human SGECs as well as IFNγ-induced pSTAT-1Y701 , pSTAT-3S727 , and PIAS-1 in mouse SGECs. CONCLUSION: JAK inhibition controls aberrant activation of SGECs and may be a novel therapeutic approach for primary SS.

Synovial cell death is regulated by TNF-α-induced expression of B-cell activating factor through an ERK-dependent increase in hypoxia-inducible factor-1α.

B-cell activating factor (BAFF) has a role in the maturation and maintenance of B cells and is associated with rheumatoid arthritis (RA). Here, we investigated whether tumor necrosis factor (TNF)-α-induced BAFF expression controls the survival of fibroblast-like synoviocytes (FLS) and whether their survival can be regulated by TNF-α-mediated upregulation of hypoxia-inducible factor (HIF)-1α using MH7A synovial cells transfected with the SV40 T antigen. More TNF-α-treated cells died compared with the control. Survival was increased by incubation with Z-VAD but inhibited after transfection with BAFF-siRNA. Both BAFF and HIF-1α expression were enhanced when MH7A cells were treated with TNF-α. TNF-α-induced BAFF expression decreased in response to HIF-1α-siRNA, whereas it increased under hypoxia or by overexpressing HIF-1α. The HIF-1α binding site on the BAFF promoter (-693 to -688 bp) was confirmed by chromatin immunoprecipitation assay to detect the -750 to -501 bp and -800 to -601 bp regions. The BAFF promoter increased in response to TNF-α treatment or overexpression of HIF-1α. However, TNF-α-induced BAFF expression and promoter activity decreased after treatment with the ERK inhibitor PD98059. Cell death was enhanced by PD98059 but was inhibited by overexpression of HIF-1α. Taken together, our results demonstrate that BAFF expression to control synovial cell survival was regulated by HIF-1α binding to the BAFF promoter, and suggest for the first time that HIF-1α might be involved in the production of inflammatory cytokines to regulate the physiological function of rheumatic FLS.

Triggering receptor expressed on myeloid cells-1 (TREM-1) deficiency augments BAFF production to promote lupus progression.

Sensing of nucleic acids by pattern recognition receptors is the key for the initiation and development of systemic lupus erythematosus (SLE). Triggering receptor expressed on myeloid cells-1 (TREM-1) is a novel innate immune receptor, which can amplify Toll-like receptor (TLR)-induced inflammatory responses. Although patients with lupus exhibit increased serum levels of soluble TREM-1 (sTREM-1), the role of TREM-1 in SLE remains unknown. In current study, we found serum sTREM-1 levels were significantly increased in lupus patients and positively correlated with disease activity. Additionally, diseased B6.lpr mice had elevated TREM-1 in the serum, spleen, and lymph nodes. To investigate the role of TREM-1 in lupus, we established Trem-1-/-.lpr mice. Trem-1-/-.lpr mice exhibited lower survival rates and more severe lupus symptoms, including elevated proteinuria, serum anti-dsDNA antibody levels, renal immune complex depositions and lymphocyte subpopulation expansions in both the spleen and lymph nodes. Besides, Trem-1-/-.lpr mice expressed higher serum B cell-activating factor (BAFF) levels and lymph node dendritic cells (DCs) were the major source of increased BAFF. Activation of membrane-bound TREM-1 could suppress TLR9-induced BAFF expression in bone marrow-derived DCs of B6.lpr mice. Moreover, levels of sTREM-1, which could act as an antagonist of membrane-bound TREM-1, were positively correlated with levels of BAFF in the sera of lupus patients. Our findings suggest a novel modulatory role of TREM-1 in the pathogenesis of SLE. sTREM-1 production is a useful diagnostic marker and a molecular target for combination therapy of lupus.

BAFF and APRIL from Activin A-Treated Dendritic Cells Upregulate the Antitumor Efficacy of Dendritic Cells In Vivo.

The members of the TGFß superfamily play a key role in regulating developmental and homeostasis programs by controlling differentiation, proliferation, polarization, and survival of different cell types. Although the role of TGFß1 in inflammation and immunity is well evident, the contribution of other TGFß family cytokines in the modulation of the antitumor immune response remains less documented. Here we show that activin A triggers SMAD2 and ERK1/2 pathways in dendritic cells (DC) expressing type I and II activin receptors, and upregulates production of the TNFα family cytokines BAFF (TALL-1, TNFSF13B) and APRIL (TALL-2, TNFSF13A), which is blocked by SMAD2 and ERK1/2 inhibitors, respectively. BAFF and APRIL derived from activin A-treated DCs upregulate proliferation and survival of T cells expressing the corresponding receptors, BAFF-R and TACI. In vivo, activin A-stimulated DCs demonstrate a significantly increased ability to induce tumor-specific CTLs and inhibit the growth of melanoma and lung carcinoma, which relies on DC-derived BAFF and APRIL, as knockdown of the BAFF and APRIL gene expression in activin A-treated DCs blocks augmentation of their antitumor potential. Although systemic administration of activin A, BAFF, or APRIL for the therapeutic purposes is not likely due to the pluripotent effects on malignant and nonmalignant cells, our data open a novel opportunity for improving the efficacy of DC vaccines. In fact, a significant augmentation of the antitumor activity of DC pretreated with activin A and the proven role of DC-derived BAFF and APRIL in the induction of antitumor immunity in vivo support this direction. Cancer Res; 76(17); 4959-69. ©2016 AACR.

Disruption of Splenic Lymphoid Tissue and Plasmacytosis in Canine Visceral Leishmaniasis: Changes in Homing and Survival of Plasma Cells.

Visceral leishmaniasis (VL) is a disease caused by Leishmania infantum, which is transmitted by phlebotomine sandflies. Dogs are the main urban reservoir of this parasite and the disease presents similar characteristics in both humans and dogs. In this paper, we investigated the potential pathways involved in plasma cell replacement of normal cell populations in the spleen, with respect to disease severity in dogs from an endemic area for visceral leishmaniasis. To this end, canine spleen samples were grouped into three categories: TYPE1SC- (non-infected dogs or without active infection with organized white pulp), TYPE1SC+ (infected dogs with organized white pulp) or TYPE3SC+ (infected animals with disorganized white pulp). We analyzed the distribution of different plasma cell isotypes (IgA, IgG and IgM) in the spleen. The expression of cytokines and chemokines involved in plasma cell homing and survival were assessed by real time RT-PCR. Polyclonal B cell activation and hypergammaglobulinemia were also evaluated. The proportion of animals with moderate or intense plasmacytosis was higher in the TYPE3SC+ group than in the other groups (Fisher test, P<0.05). This was mainly due to a higher density of IgG+ plasma cells in the red pulp of this group. The albumin/globulin ratio was lower in the TYPE3SC+ animals than in the TYPE1SC- or TYPE1SC+ animals, which evidences VL-associated dysproteinemia. Interestingly, TYPE3SC+ animals showed increased expression of the BAFF and APRIL cytokines, as well as chemokine CXCL12. Aberrant expression of BAFF, APRIL and CXCL12, together with amplified extrafollicular B cell activation, lead to plasma cell homing and the extended survival of these cells in the splenic red pulp compartment. These changes in the distribution of immunocompetent cells in the spleen may contribute to the progression of VL, and impair the spleen's ability to protect against blood borne pathogens.

A benzenediamine derivate FC-99 attenuates lupus nephritis in MRL/lpr mice via inhibiting myeloid dendritic cell-secreted BAFF.

Myeloid dendritic cells (DCs) can produce B-cell-activating factor (BAFF) that modulates survival and differentiation of B cells and plays a pivotal role in the pathogenesis of systemic lupus erythematosus (SLE). Toll-like receptor 4 (TLR4) signaling has important functions in the process of BAFF production. Our previous study showed that a benzenediamine derivate FC-99 possesses anti-inflammation activity and directly interacts with interleukin-1 receptor-associated kinase 4 (IRAK4), which was a pivotal molecule in TLR4 signaling. In this study, we demonstrated that FC-99 attenuated lupus nephritis in the MRL/lpr mice. FC-99 also decreased the levels of total immunoglobulin G (IgG), total IgG2a and IgM in sera, as well as the activation of B cells in the spleens of MRL/lpr mice. Moreover, FC-99 inhibited abnormal activation of myeloid DCs in spleens and reduced the levels of BAFF in sera, spleens, and kidneys of MRL/lpr mice. Furthermore, upon TLR4 stimulation with lipopolysaccharide in vitro, FC-99 inhibited IRAK4 phosphorylation, as well as the activation and BAFF production in murine bone marrow-derived DCs. These data indicate that FC-99 attenuates lupus nephritis in MRL/lpr mice via inhibiting DC-secreted BAFF, suggesting that FC-99 may be a potential therapeutic candidate for the treatment of SLE.

Significance of BAFF/APRIL Expression and Their Receptors in Pediatric Patients With Acute Lymphoblastic Leukemia.

In this study, we investigated the mRNA expression and protein levels of B-cell activating factor (BAFF)/a proliferation-inducing ligand (APRIL) and their receptors in acute lymphoblastic leukemia (ALL) cell lines and pediatric patients with ALL using real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and Western blotting. The location and level of the BAFF/APRIL proteins in ALL cell lines were also detected by immunofluorescence cytochemistry and flow cytometry. Correlations between plasma protein levels of BAFF/APRIL and primary clinical parameters were analyzed. We found that BAFF/APRIL was highly expressed in pediatric ALL patients and ALL cell lines. The BAFF/APRIL proteins were located on the cell membrane, and the proportion of positive cells and mean fluorescence intensity were significantly higher than in the healthy control group (P<0.05). The mRNA expression and protein levels of BAFF/APRIL and their receptors in untreated ALL children were significantly higher than in healthy controls (P<0.05) as well as were significantly reduced in the remission group (P<0.05). The plasma protein levels of BAFF/APRIL were positively correlated with the white blood cell count, lactate dehydrogenase, and serum ferritin. Abnormal levels of BAFF/APRIL in pediatric ALL suggest that BAFF/APRIL are associated with the development and progression of ALL in children and may provide information for the development of BAFF-based and APRIL-based targeted therapies.

Infusion of CD3/CD28 costimulated umbilical cord blood T cells at the time of single umbilical cord blood transplantation may enhance engraftment.

Limited cell numbers in umbilical cord blood (UCB) grafts present a major impediment to favorable outcomes in adult transplantation, largely related to delayed or failed engraftment. The advent of UCB transplantation (UCBT) using two grafts successfully circumvents this obstacle, despite the engraftment of only one unit. Preclinical models suggested that the addition of UCB T cells at the time of transplant can enhance engraftment. We tested whether ex vivo activation by CD3/CD28 costimulation and expansion of T cells from a single UCB graft would be safe and feasible in adults with advanced hematologic malignancies, with an overall objective of optimizing engraftment in single unit UCBT. In this phase 1 study, recipients of single UCB units were eligible if the unit was stored in two adequate fractions. Dose limiting toxicity was defined as grade 3 or grade 4 GVHD within 90 days of UCBT. Four patients underwent UCBT; all were treated at the first dose level (10(5) cells/kg). At the 10(5) cells/kg dose level two subjects experienced grade 3 intestinal GVHD, thus meeting stopping criteria. For three subjects, neutrophil engraftment was early (12, 17, and 20 days), while one subject experienced primary graft failure. We observed early donor T cell trafficking and found that expanded T cells produced supraphysiologic levels of cytokines relevant to engraftment and to lymphoid differentiation and function. Taken together, these preliminary data suggest rapid engraftment in recipients of a single UCBT combined with relatively low doses of activated T cells, though potentially complicated by severe GVHD.

Exploring BAFF: its expression, receptors and contribution to the immunopathogenesis of Sjögren's syndrome.

SS is an autoimmune condition characterized by exocrine gland destruction, autoantibody production, immune complex deposition and systemic complications associated with lymphocytic infiltration of many organs. Genetic, environmental and viral factors play a role in disease aetiology, however, the exact mechanisms driving the immunopathogenesis of SS remain uncertain. Here we discuss a role for B cell activating factor (BAFF), whereby B cell hyperactivity and increased BAFF secretion observed in patients and animal models of the disease can be explained by the altered expression of cell-specific BAFF/BAFF receptor (BAFF-R) variants in several immune cell types. Understanding the role of BAFF/BAFF-R heterogeneity in SS pathogenesis could help to facilitate new treatment strategies for patients.

Plasmacytoid dendritic cells and myeloid cells differently contribute to B-cell-activating factor belonging to the tumor necrosis factor superfamily overexpression during primary HIV infection.

BACKGROUND: After describing heightened levels of circulating B-cell-activating factor belonging to the tumor necrosis factor superfamily (BAFF) as well as changes in B-cell phenotype and functions during acute infection by simian immunodeficiency virus, we wanted to determine whether and by which cells BAFF was over-expressed in primary HIV-infected (PHI) patients. DESIGN AND METHODS: We simultaneously examined circulating BAFF levels by ELISA and membrane-bound BAFF (mBAFF) expression by flow cytometry in peripheral blood mononuclear cells of healthy donors and PHI patients followed for 6 months. We also examined whether HIV-1 modifies BAFF expression or release in various myeloid cells and plasmacytoid dendritic cells (pDC) in vitro. RESULTS: Circulating BAFF levels were transiently increased at enrolment. They positively correlated with CXCL10 levels and inversely with B-cell counts. Whereas mBAFF was expressed by most pDC and on a fraction of intermediate monocytes in healthy donors, the frequency of mBAFF cells significantly increased among nonclassical monocytes and CD1c dendritic cells but decreased among pDC in PHI patients. In contrast to myeloid cells, pDC never released BAFF upon stimulation. Their mBAFF expression was enhanced by HIV-1, independently of type I IFN. CONCLUSION: Our findings reveal that the pattern of BAFF expression by myeloid cells and pDC is altered in PHI patients and constitutes a valuable marker of immune activation whose circulating levels correlate with CXCL10 levels. Due to their homing in different tissue areas, pDC and myeloid cells might target different B-cell subsets through their mBAFF expression or soluble BAFF release.

IgG-Immune Complexes Promote B Cell Memory by Inducing BAFF.

Memory B cell responses are vital for protection against infections but must also be regulated to prevent autoimmunity. Cognate T cell help, somatic hypermutation, and affinity maturation within germinal centers (GCs) are required for high-affinity memory B cell formation; however, the signals that commit GC B cells to the memory pool remain unclear. In this study, we identify a role for IgG-immune complexes (ICs), FcγRs, and BAFF during the formation of memory B cells in mice. We found that early secretion of IgG in response to immunization with a T-dependent Ag leads to IC-FcγR interactions that induce dendritic cells to secrete BAFF, which acts at or upstream of Bcl-6 in activated B cells. Loss of CD16, hematopoietic cell-derived BAFF, or blocking IC:FcγR regions in vivo diminished the expression of Bcl-6, the frequency of GC and memory B cells, and secondary Ab responses. BAFF also contributed to the maintenance and/or expansion of the follicular helper T cell population, although it was dispensable for their formation. Thus, early Ab responses contribute to the optimal formation of B cell memory through IgG-ICs and BAFF. Our work defines a new role for FcγRs in GC and memory B cell responses.

The interferon type I signature is present in systemic sclerosis before overt fibrosis and might contribute to its pathogenesis through high BAFF gene expression and high collagen synthesis.

BACKGROUND: Interferon (IFN) signature has been reported in definite systemic sclerosis (SSc) but it has not been characterised in early SSc (EaSSc). We aim at characterising IFN type I signature in SSc before overt skin fibrosis develops. METHODS: The expression of 11 IFN type I inducible genes was tested in whole-blood samples from 30 healthy controls (HCs), 12 subjects with primary Raynaud's phenomenon (RP), 19 patients with EaSSc, 7 patients with definite SSc without cutaneous fibrosis, 21 limited cutaneous SSc and 10 diffuse cutaneous SSc subjects. The correlation between IFN activity in monocytes, B cell activating factor (BAFF) mRNA expression and type III procollagen N-terminal propeptide (PIIINP) serum levels was tested. RESULTS: In all the SSc groups, higher IFN scores were observed compared with HC. An IFN score ≥7.09 discriminated HCs from patients with SSc (sensitivity=0.7, specificity=0.88, area under receiving operating characteristic (AUROC)=0.82); the prevalence of an elevated IFN score was: HC=3.3%; RP=33.3%, EaSSc=78.9%, definite SSc=100%, limited cutaneous SSc=42.9%, diffuse cutaneous SSc=70.0%. In monocytes an IFN score ≥4.12 distinguished HCs from patients with fibrotic SSc (sensitivity=0.62, specificity=0.85, AUROC=0.76). Compared with IFN-negative subjects, IFN-positive subjects had higher monocyte BAFF mRNA levels (19.7±5.2 vs 15.20±4.0, p=2.1×10(-5)) and serum PIIINP levels (median=6.0 (IQR 5.4-8.9) vs median=3.9 (IQR 3.3-4.7), p=0.0004). CONCLUSIONS: An IFN type I signature is observed in patients with SSc from the earliest phases of the disease, even before overt skin fibrosis. The presence of IFN type I signature in monocytes is correlated with BAFF mRNA expression and serum PIIINP levels, supporting a contribution in the pathogenesis and progression of SSc.

Targeting bone marrow lymphoid niches in acute lymphoblastic leukemia.

In acute lymphoblastic leukemia (ALL) the bone marrow microenvironment provides growth and survival signals that may confer resistance to chemotherapy. Granulocyte colony-stimulating factor (G-CSF) potently inhibits lymphopoiesis by targeting stromal cells that comprise the lymphoid niche in the bone marrow. To determine whether lymphoid niche disruption by G-CSF sensitizes ALL cells to chemotherapy, we conducted a pilot study of G-CSF in combination with chemotherapy in patients with relapsed or refractory ALL. Thirteen patients were treated on study; three patients achieved a complete remission (CR/CRi) for an overall response rate of 23%. In the healthy volunteers, G-CSF treatment disrupted the lymphoid niche, as evidenced by reduced expression of CXCL12, interleukin-7, and osteocalcin. However, in most patients with relapsed/refractory ALL expression of these genes was markedly suppressed at baseline. Thus, although G-CSF treatment was associated with ALL cell mobilization into the blood, and increased apoptosis of bone marrow resident ALL cells, alterations in the bone marrow microenvironment were modest and highly variable. These data suggest that disruption of lymphoid niches by G-CSF to sensitize ALL cells to chemotherapy may be best accomplished in the consolidation where the bone marrow microenvironment is more likely to be normal.

Increase of Intracellular BAFF in B Cells of Sjögren's Patients Is Not Affected by Decrease of BAFFR.

The presence of a broad spectrum of autoantibodies in Sjögren's syndrome (SjS) patients is the result of abnormal B-cell regulation that can be at least partially explained by abnormal BAFF/BAFFR regulation. The objective of this study was to determine both membrane and intracellular expression of BAFF/BAFFR in monocytes and B-cells in peripheral blood of 19 primary Sjögren's syndrome patients and 20 healthy controls using flow cytometry. We also measured sBAFF in serum. Compared to healthy controls, both surface and intracellular expression of BAFF was significantly increased in monocytes and B-cells of SjS patients. Also serum sBAFF level was elevated. Expression of BAFFR on B-cells of SjS patients was surprisingly decreased, but there was no clear increase or decrease within monocytes. Our results indicate that activated monocytes communicate with B-cells via BAFF and BAFFR, so that B-cells are stimulated, but BAFF is also produced to stimulate cells in autocrine way. The decrease of BAFFR expression in SjS patients suggests that there is the mechanism that attempts to take over in order to balance the high level of BAFF.