Showing papers on "B-cell activating factor published in 2013"

Prevalence of interferon type I signature in CD14 monocytes of patients with Sjögren's syndrome and association with disease activity and BAFF gene expression

Abstract: Objective To determine the prevalence of upregulation of interferon (IFN) type I inducible genes, the so called ‘IFN type I signature’, in CD14 monocytes in 69 patients with primary Sjogren’s syndrome (pSS) and 44 healthy controls (HC) and correlate it with disease manifestations and expression of B cell activating factor (BAFF). Methods Expression of IFI44L, IFI44, IFIT3, LY6E and MX1 was measured using real time quantitative PCR in monocytes. Expression values were used to calculate IFN type I scores for each subject. pSS patients positive for the IFN type I signature (IFN score≥10) and patients negative for the signature (IFN score<10) were then compared for clinical disease manifestations and BAFF expression. A bioassay using a monocytic cell line was performed to study whether BAFF mRNA expression was inducible by IFN type I activity in serum of patients with pSS. Results An IFN type I signature was present in 55% of patients with pSS compared with 4.5% of HC. Patients with the IFN type I signature showed: (a) higher EULAR Sjogren’s Syndrome Disease Activity Index scores; higher anti-Ro52, anti-Ro60 and anti-La autoantibodies; higher rheumatoid factor; higher serum IgG; lower C3, lower absolute lymphocyte and neutrophil counts; (b)higher BAFF gene expression in monocytes. In addition, serum of signature-positive patients induced BAFF gene expression in monocytes. Conclusions The monocyte IFN type I signature identifies a subgroup of patients with pSS with a higher clinical disease activity together with higher BAFF mRNA expression. Such patients might benefit from treatment blocking IFN type I production or activity.

Plasma B Lymphocyte Stimulator and B Cell Differentiation in Idiopathic Pulmonary Fibrosis Patients

Abstract: We hypothesized B cells are involved in the pathogenesis of idiopathic pulmonary fibrosis (IPF), a progressive, restrictive lung disease that is refractory to glucocorticoids and other nonspecific therapies, and almost invariably lethal. Accordingly, we sought to identify clinically associated B cell–related abnormalities in these patients. Phenotypes of circulating B cells were characterized by flow cytometry. Intrapulmonary processes were evaluated by immunohistochemistry. Plasma B lymphocyte stimulating factor (BLyS) was assayed by ELISA. Circulating B cells of IPF subjects were more Ag differentiated, with greater plasmablast proportions (3.1 ± 0.8%) than in normal controls (1.3 ± 0.3%) ( p < 0.03), and the extent of this differentiation correlated with IPF patient lung volumes ( r = 0.44, p < 0.03). CD20+ B cell aggregates, diffuse parenchymal and perivascular immune complexes, and complement depositions were all prevalent in IPF lungs, but much less prominent or absent in normal lungs. Plasma concentrations of BLyS, an obligate factor for B cell survival and differentiation, were significantly greater ( p < 0.0001) in 110 IPF (2.05 ± 0.05 ng/ml) than among 53 normal (1.40 ± 0.04 ng/ml) and 90 chronic obstructive pulmonary disease subjects (1.59 ± 0.05 ng/ml). BLyS levels were uniquely correlated among IPF patients with pulmonary artery pressures ( r = 0.58, p < 0.0001). The 25% of IPF subjects with the greatest BLyS values also had diminished 1-y survival (46 ± 11%), compared with those with lesser BLyS concentrations (81 ± 5%) (hazard ratio = 4.0, 95% confidence interval = 1.8–8.7, p = 0.0002). Abnormalities of B cells and BLyS are common in IPF patients, and highly associated with disease manifestations and patient outcomes. These findings have implications regarding IPF pathogenesis and illuminate the potential for novel treatment regimens that specifically target B cells in patients with this lung disease.

Elevated serum BAFF levels are associated with rising anti-double-stranded DNA antibody levels and disease flare following B cell depletion therapy in systemic lupus erythematosus.

Abstract: Objective To determine whether serum BAFF levels correlate with relapse or remission in patients with systemic lupus erythematosus (SLE) following B cell depletion therapy (BCDT) and to assess the relationship between serum BAFF levels, B cell numbers, and immunoglobulin and autoantibody levels during active disease, both before and after BCDT. Methods Thirty-five patients with active SLE underwent BCDT with rituximab and were monitored for a minimum of 18 months, using clinical and serologic measures of disease activity. Serum BAFF was measured sequentially by enzyme-linked immunosorbent assay before BCDT and during disease relapse or remission after B cell repopulation. Results Serum BAFF levels prior to BCDT correlated positively with the numbers of CD19+ B cells and with the levels of IgG and IgA. Following BCDT and subsequent B cell repopulation, BAFF levels were significantly higher during relapse, as compared with disease remission, and were significantly greater than at disease flare prior to BCDT. At the time of relapse after BCDT, serum BAFF levels were inversely correlated with B cell numbers, with flare at lower B cell numbers being associated with the highest BAFF levels. The correlations between serum BAFF levels and levels of IgG and IgA were lost following BCDT, but changes in serum BAFF levels correlated positively with changes in anti–double-stranded DNA (anti-dsDNA) antibody levels during relapse or remission after BCDT. Conclusion The present findings suggest a significant role of BAFF in driving disease flare after B cell repopulation following BCDT. Sequential BCDT may promote ever-increasing levels of BAFF, accompanied by rising anti-dsDNA antibody levels and disease flare even at low B cell numbers. Therefore, our data justify the judicious use of BAFF blockade in a subgroup of lupus patients after BCDT.

CVID-associated TACI mutations affect autoreactive B cell selection and activation

Abstract: Common variable immune deficiency (CVID) is an assorted group of primary diseases that clinically manifest with antibody deficiency, infection susceptibility, and autoimmunity. Heterozygous mutations in the gene encoding the tumor necrosis factor receptor superfamily member TACI are associated with CVID and autoimmune manifestations, whereas two mutated alleles prevent autoimmunity. To assess how the number of TACI mutations affects B cell activation and tolerance checkpoints, we analyzed healthy individuals and CVID patients carrying one or two TACI mutations. We found that TACI interacts with the cleaved, mature forms of TLR7 and TLR9 and plays an important role during B cell activation and the central removal of autoreactive B cells in healthy donors and CVID patients. However, only subjects with a single TACI mutation displayed a breached immune tolerance and secreted antinuclear antibodies (ANAs). These antibodies were associated with the presence of circulating B cell lymphoma 6–expressing T follicular helper (Tfh) cells, likely stimulating autoreactive B cells. Thus, TACI mutations may favor CVID by altering B cell activation with coincident impairment of central B cell tolerance, whereas residual B cell responsiveness in patients with one, but not two, TACI mutations enables autoimmune complications.

Clinical associations of serum interleukin-17 in systemic lupus erythematosus

Abstract: Serum interleukin (IL)-17 concentrations have been reported to be increased in systemic lupus erythematosus (SLE), but associations with clinical characteristics are not well understood. We characterized clinical associations of serum IL-17 in SLE. We quantified IL-17 in serum samples from 98 SLE patients studied cross-sectionally, and in 246 samples from 75 of these patients followed longitudinally over two years. Disease activity was recorded using the SLE Disease Activity Index (SLEDAI)-2k. Serum IL-6, migration inhibitory factor (MIF), and B cell activating factor of the tumour necrosis factor family (BAFF) were also measured in these samples. Serum IL-17 levels were significantly higher in SLE patients compared to healthy donors (P <0.0001). No correlation was observed between serum IL-17 and SLEDAI-2k, at baseline or during longitudinal follow-up. However, we observed that SLEDAI-2k was positively correlated with IL-17/IL-6 ratio. Serum IL-17 was significantly increased in SLE patients with central nervous system (CNS) disease (P = 0.0298). A strong correlation was observed between serum IL-17 and IL-6 (r = 0.62, P <0.0001), and this relationship was observed regardless of disease activity and persisted when integrating cytokine levels over the period observed (r = 0.66, P <0.0001). A strong correlation of serum IL-17 was also observed with serum BAFF (r = 0.64, P <0.0001), and MIF (r = 0.36, P = 0.0016). Serum IL-17 concentration correlates poorly with SLE disease activity but is significantly elevated in patients with CNS disease. IL-17/IL-6 ratio may be more useful than IL-17 or IL-6 alone to characterize Th17-driven disease, such as SLE. The association of other cytokines with serum IL-17 suggests that IL-17 may drive activation of diverse immune pathways in SLE.

B lymphocytes and B-cell activating factor promote collagen and profibrotic markers expression by dermal fibroblasts in systemic sclerosis.

Abstract: B lymphocytes might play a pathogenic role in dermal fibrosis in systemic sclerosis (SSc). B-cell activating factor (BAFF), a key cytokine for B-cell activation, is increased in the serum and the skin of patients with SSc. However, the ability of B cells directly to stimulate dermal fibroblasts and the role of BAFF are not fully understood. We therefore investigated the involvement of B cells and BAFF in the expression of collagen and profibrotic markers by dermal fibroblasts. Cocultures of blood B cells from healthy blood donors and normal or SSc dermal fibroblasts stimulated with anti-IgM and BAFF were performed. Alpha-SMA, TIMP1, MMP9, COL1A1, COL1A2, and COL3A1 mRNA expression were determined by quantitative RT-PCR. Soluble collagen, BAFF, IL-6, IL-1β, TGF-β1, and CCL2 protein secretion were assessed. Coculture of blood B cells and dermal fibroblasts isolated from SSc patients induced IL-6, TGF-β1, CCL2, and collagen secretion, as well as Alpha-SMA, TIMP1, and MMP9 expression in dermal fibroblasts. Transwell assays demonstrated that this induction was dependent on cell-cell contact. Addition of anti-IgM and BAFF to the coculture increased IL-6, CCL2, TGF-β1, and collagen secretion. B cell- and BAFF-induced collagen secretion was highly reduced by anti-TGF-β1 antibodies. Our results showed for the first time a direct role of B cells on the production of collagen by dermal fibroblasts, which is further enhanced by BAFF. Thus, these results demonstrate a new pathogenic role of B cells and BAFF in fibrosis and systemic sclerosis.

Toll-like receptor activation in basophils contributes to the development of IgG4-related disease

Abstract: IgG4-related disease (IRD) is characterized by systemic IgG4 antibody responses and by infiltration of IgG4-expressing plasma cells into the affected organs. Although T helper type 2 (Th2) cytokines are implicated in enhanced IgG4 responses, molecular mechanisms accounting for the development of IgG4 antibody responses are poorly defined. Since basophils function as antigen-presenting cells for Th2 responses, we tried to clarify the role of basophils in the development of IgG4 responses in this study. IgG4 and cytokine responses to various nucleotide-binding oligomerization domain-like receptor and Toll-like receptor (TLR) ligands were examined by using basophils isolated from healthy controls and from patients with IgG4-related disease. Activation of TLRs in basophils from healthy controls induced IgG4 production by B cells, which effect was associated with enhanced production of B cell activating factor (BAFF) and IL-13. In addition, activation of TLRs in basophils from patients with IRD induced a large amount of IgG4 by B cells from healthy controls. This enhancement of IgG4 production was again associated with BAFF and IL-13. These data suggest that innate immune responses mediated through TLRs may play a role in the development of IgG4-related disease, in part by production of BAFF from basophils.

Protein microarray analysis reveals BAFF-binding autoantibodies in systemic lupus erythematosus.

Abstract: Autoantibodies against cytokines, chemokines, and growth factors inhibit normal immunity and are implicated in inflammatory autoimmune disease and diseases of immune deficiency. In an effort to evaluate serum from autoimmune and immunodeficient patients for Abs against cytokines, chemokines, and growth factors in a high-throughput and unbiased manner, we constructed a multiplex protein microarray for detection of serum factor-binding Abs and used the microarray to detect autoantibody targets in SLE. We designed a nitrocellulose-surface microarray containing human cytokines, chemokines, and other circulating proteins and demonstrated that the array permitted specific detection of serum factor-binding probes. We used the arrays to detect previously described autoantibodies against cytokines in samples from individuals with autoimmune polyendocrine syndrome type 1 and chronic mycobacterial infection. Serum profiling from individuals with SLE revealed that among several targets, elevated IgG autoantibody reactivity to B cell-activating factor (BAFF) was associated with SLE compared with control samples. BAFF reactivity correlated with the severity of disease-associated features, including IFN-α-driven SLE pathology. Our results showed that serum factor protein microarrays facilitate detection of autoantibody reactivity to serum factors in human samples and that BAFF-reactive autoantibodies may be associated with an elevated inflammatory disease state within the spectrum of SLE.

Association of serum B cell activating factor from the tumour necrosis factor family (BAFF) and a proliferation-inducing ligand (APRIL) with central nervous system and renal disease in systemic lupus erythematosus.

Abstract: IntroductionThe objective of this study is to determine whether serum concentrations of B cell activating factor from the tumour necrosis factor family (BAFF) and/or a proliferation-inducing ligand...

B-cell-targeted therapies in systemic lupus erythematosus.

Abstract: Autoreactive B cells are one of the key immune cells that have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). In addition to the production of harmful auto-antibodies (auto-Abs), B cells prime autoreactive T cells as antigen-presenting cells and secrete a wide range of pro-inflammatory cytokines that have both autocrine and paracrine effects. Agents that modulate B cells may therefore be of potential therapeutic value. Current strategies include targeting B-cell surface antigens, cytokines that promote B-cell growth and functions, and B- and T-cell interactions. In this article, we review the role of B cells in SLE in animal and human studies, and we examine previous reports that support B-cell modulation as a promising strategy for the treatment of this condition. In addition, we present an update on the clinical trials that have evaluated the therapeutic efficacy and safety of agents that antagonize CD20, CD22 and B-lymphocyte stimulator (BLyS) in human SLE. While the results of many of these studies remain inconclusive, belimumab, a human monoclonal antibody against BLyS, has shown promise and has recently been approved by the US Food and Drug Administration as an indicated therapy for patients with mild to moderate SLE. Undoubtedly, advances in B-cell immunology will continue to lead us to a better understanding of SLE pathogenesis and the development of novel specific therapies that target B cells.

B cell survival, surface BCR and BAFFR expression, CD74 metabolism, and CD8- dendritic cells require the intramembrane endopeptidase SPPL2A.

Abstract: Druggable proteins required for B lymphocyte survival and immune responses are an emerging source of new treatments for autoimmunity and lymphoid malignancy. In this study, we show that mice with an inactivating mutation in the intramembrane protease signal peptide peptidase-like 2A (SPPL2A) unexpectedly exhibit profound humoral immunodeficiency and lack mature B cell subsets, mirroring deficiency of the cytokine B cell-activating factor (BAFF). Accumulation of Sppl2a-deficient B cells was rescued by overexpression of the BAFF-induced survival protein B cell lymphoma 2 (BCL2) but not BAFF and was distinguished by low surface BAFF receptor and IgM and IgD B cell receptors. CD8-negative dendritic cells were also greatly decreased. SPPL2A deficiency blocked the proteolytic processing of CD74 MHC II invariant chain in both cell types, causing dramatic build-up of the p8 product of Cathepsin S and interfering with earlier steps in CD74 endosomal retention and processing. The findings illuminate an important role for the final step in the CD74-MHC II pathway and a new target for protease inhibitor treatment of B cell diseases.

TACI mutations and impaired B-cell function in subjects with CVID and healthy heterozygotes.

Abstract: Background Mutations in the gene coding for the transmembrane activator and calcium-modulating cyclophilin ligand interactor ( TACI ) are found in 8% to 10% of subjects with common variable immunodeficiency (CVID). Although heterozygous mutations may coincide with immunodeficiency in a few families, most mutation-bearing relatives are not hypogammaglobulinemic. Thus, the role of TACI mutations in producing the immune defect remains unclear. Objective This study examined the expression and function of TACI mutations in healthy heterozygous relatives. Methods We examined the surface and intracellular expression of TACI protein in EBV-transformed B cells of patients and relatives with mutations in 7 families, binding of a proliferation-inducing ligand, and secretion of IgG and IgA by ligand-activated B cells. We tested whether Toll-like receptor 9 agonists increased TACI expression and whether an agonistic anti-TACI antibody could induce activation-induced cytidine deaminase mRNA in those with mutations. Results Intracellular and extracellular TACI expression was defective for B cells of all subjects with mutations, including subjects with CVID and relatives. Although Toll-like receptor 9 triggering normally up-regulates B-cell TACI expression, this was defective for all subjects with mutations. Triggering TACI by an agonistic antibody showed loss of activation-induced cytidine deaminase mRNA induction in all mutation-bearing B cells. However, ligand-induced IgG and IgA production was normal for healthy relatives but not for subjects with CVID. Conclusion Thus, B cells of relatives of subjects with CVID who have mutations in TACI but normal immune globulin levels still have detectable in vitro B-cell defects.

Cyclophosphamide Induces a Type I Interferon–Associated Sterile Inflammatory Response Signature in Cancer Patients' Blood Cells: Implications for Cancer Chemoimmunotherapy

Abstract: Purpose: Certain chemotherapeutics, particularly cyclophosphamide, can enhance the antitumor efficacy of immunotherapy. A better understanding of the cellular and molecular basis of cyclophosphamide-mediated immunomodulation is needed to improve the efficacy of chemoimmunotherapy. Experimental Design: Transcript profiling and flow cytometry were used to explore cyclophosphamide-induced immunoadjuvanticity in patients with hematologic malignancies. Results: A single high-dose treatment rapidly (1–2 days) induced peripheral blood mononuclear cell (PBMC) transcriptional modulation, leading to reduction of cell-cycle and biosynthetic/metabolic processes and augmentation of DNA damage and cell death pathways (p53 signaling pathway), death-related scavenger receptors, antigen processing/presentation mediators, T-cell activation markers and, noticeably, a type I IFN (IFN-I) signature ( OAS1 , CXCL10 , BAFF , IFITM2 , IFI6 , IRF5 , IRF7 , STAT2 , UBE2L6 , UNC93B1 , ISG20L1 , TYK2 ). Moreover, IFN-I–induced proinflammatory mediators (CXCL10, CCL2, IL-8, and BAFF) were increased in patients9 plasma. Accordingly, cyclophosphamide induced the expansion/activation of CD14 + CD16 + monocytes, of HLA-DR + , IL-8RA + , and MARCO + monocytes/dendritic cells, and of CD69 + , OX40 + , and IL-8RA + lymphocytes. Conclusions: Altogether, these data identify the cyclophosphamide-induced immunomodulatory factors in humans and indicate that preconditioning chemotherapy may stimulate immunity as a consequence of danger perception associated with blood cell death, through p53 and IFN-I–related mechanisms. Clin Cancer Res; 19(15); 4249–61. ©2013 AACR .

Dual functional BAFF receptor aptamers inhibit ligand-induced proliferation and deliver siRNAs to NHL cells

Abstract: The B-cell–activating factor (BAFF)-receptor (BAFF-R) is restrictedly expressed on B-cells and is often overexpressed in B-cell malignancies, such as non-Hodgkin’s lymphoma. On binding to its ligand BAFF, proliferation and cell survival are increased, enabling cancer cells to proliferate faster than normal B-cells. Nucleic acid aptamers can bind to target ligands with high specificity and affinity and may offer therapeutic advantages over antibody-based approaches. In this study, we isolated several 2′-F–modified RNA aptamers targeting the B-cell–specific BAFF-R with nanomolar affinity using in vitro SELEX technology. The aptamers efficiently bound to BAFF-R on the surface of B-cells, blocked BAFF-mediated B-cell proliferation and were internalized into B-cells. Furthermore, chimeric molecules between the BAFF-R aptamer and small interfering RNAs (siRNAs) were specifically delivered to BAFF-R expressing cells with a similar efficiency as the aptamer alone. We demonstrate that a signal transducer and activator of transcription 3 (STAT3) siRNA delivered by the BAFF-R aptamer was processed by Dicer and efficiently reduced levels of target mRNA and protein in Jeko-1 and Z138 human B-cell lines. Collectively, our results demonstrate that the dual-functional BAFF-R aptamer–siRNA conjugates are able to deliver siRNAs and block ligand mediated processes, suggesting it might be a promising combinatorial therapeutic agent for B-cell malignancies.

Curcumin Protects Against Collagen-Induced Arthritis via Suppression of BAFF Production

Abstract: Purpose The aim of the present study was to evaluate whether the anti-Rheumatoid arthritis (RA) effect of curcumin is associated with the regulation of B cell-activating factor belonging to the TNF family (BAFF) production.

Antibody deficiency associated with an inherited autosomal dominant mutation in TWEAK

Abstract: Mutations in the TNF family of proteins have been associated with inherited forms of immune deficiency. Using an array-based sequencing assay, we identified an autosomal-dominant deficiency in TNF-like weak inducer of apoptosis (TWEAK; TNFSF12) in a kindred with recurrent infection and impaired antibody responses to protein and polysaccharide vaccines. This mutation occurs in the sixth exon of TWEAK and results in the amino acid substitution R145C within the conserved TNF-homology domain of the full-length protein. TWEAK mutant protein formed high molecular weight aggregates under nonreducing conditions, suggesting an increased propensity for intermolecular interactions. As a result, mutant TWEAK associated with B-cell–activating factor (BAFF) protein and down-regulated the BAFF-mediated activation of the noncanonical NF-κB pathway through inhibition of p100 processing to p52, resulting in inhibition of BAFF-dependent B-cell survival and proliferation. As BAFF mediates T-cell–independent isotype switching and B-cell survival, our data implicate TWEAK as a disease-susceptibility gene for a humoral immunodeficiency.

Serum BAFF is elevated in patients with IgA nephropathy and associated with clinical and histopathological features.

Abstract: BACKGROUND B-cell-activating factor belonging to the tumor necrosis factor family (BAFF) has been found to have the function of activating B cells and participating in the class switching of B cells; however, its clinical application needs further study. In the present study, the serum BAFF levels of patients with IgA nephropathy (IgAN) with different histopathological phenotypes were measured. METHODS Levels of serum BAFF in 153 patients with IgAN, 55 healthy controls and 20 disease controls were recorded using commercially available ELISA kits. Their correlations with clinical and histopathological features of patients with IgAN were further evaluated. RESULTS Levels of serum BAFF in patients with IgAN were significantly higher than in controls. Serum BAFF levels were significantly higher in patients with mesangial hypercellularity and segmental glomerulosclerosis than in those without. Serum BAFF levels were associated with the severity of tubular atrophy/interstitial fibrosis. Serum BAFF levels were significantly positively correlated with estimated glomerular filtration rate and serum creatinine. Patients with elevated serum BAFF levels showed significantly greater severity in clinical and histopathological stages. CONCLUSION Levels of serum BAFF were elevated in patients with IgAN and were associated with clinical and pathological features of the disease. Serum BAFF levels could be a noninvasive biomarker for monitoring disease severity of IgAN.

In Kidney Transplant Patients, Alemtuzumab but Not Basiliximab/Low-Dose Rabbit Anti-Thymocyte Globulin Induces B Cell Depletion and Regeneration, Which Associates with a High Incidence of De Novo Donor-Specific Anti-HLA Antibody Development

Abstract: In this single-center matched-cohort study, we evaluated the phenotype of repopulating B cells and its correlation with donor-specific anti-HLA Ab development and long-term graft function in 16 renal transplant recipients and 32 age- and gender-matched controls induced with alemtuzumab or basiliximab (Bas)/low-dose rabbit anti-thymocyte globulin (rATG), respectively. Alemtuzumab, but not Bas/rATG, profoundly depleted peripheral B cells in the first 2 mo posttransplantation. Early posttransplant, naive B cells were significantly depleted, whereas Ag-experienced and memory B cells were partially spared. Transitional B cells transiently increased 2 mo posttransplant. At month 6 posttransplant, pregerminal center B cells emerged, a process promoted by increased BAFF serum levels. Thereafter, B cell counts increased progressively, mainly due to expansion of naive B cells. Conversely, Bas/rATG did not modify the B cell phenotype throughout the follow-up period. Alemtuzumab was associated with a higher incidence of de novo DSA compared with Bas/rATG. DSA development was predicted by changes in the B cell compartment and correlated with worse long-term graft function. Thus, alemtuzumab-induced B cell depletion/reconstitution may promote chronic humoral responses against the graft.

Elevated pretransplantation soluble BAFF is associated with an increased risk of acute antibody-mediated rejection.

Abstract: There is increasing interest in B cells in transplantation, with studies indicating a role in acute and chronic antibody-mediated rejection (AMR) and transplant tolerance (1–3). B-cell activating factor belonging to the tumor necrosis factor family (BAFF; also known as BLyS, TALL-1, and THANK) is a cytokine that enhances B-cell survival and proliferation (4). It exists in both a membrane-bound form and as a soluble trimer and is produced by monocytes, macrophages, dendritic cells (DCs), and, to a lesser extent, T cells (4, 5). There are three BAFF receptors: BAFF-R (also known as BR3), TACI (transmembrane activator and calcium modulator and cyclophilin ligand interactor), and BCMA (B-cell maturation antigen) (4). These are principally expressed on cells of the B-cell lineage, including plasma cells (6). In addition, BAFF-R is expressed on some activated and regulatory T cells (6, 7). The cytokine APRIL (a proliferation-inducing ligand) also uses TACI and BCMA. The importance of BAFF in B-cell biology and B-cell–mediated autoimmune diseases has been demonstrated by studies in humans and mice. Transgenic mice that overexpress BAFF have increased B-cell survival, hypergammaglobulinemia, and pathogenic autoantibodies (which arise independently of T-cell help) and spontaneously develop a lupus-like autoimmune disease (8). Furthermore, elevated serum BAFF levels have been described in patients with autoantibody-associated autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis, Sjogren’s syndrome, and idiopathic thrombocytopenic purpura (9–11). Studies of BAFF in the context of solid-organ transplantation are less frequent; in a murine cardiac allograft model, BAFF-deficient recipients had extended transplant survival, particularly if a calcineurin inhibitor was administered (7). The deleterious effect of BAFF on allograft survival in this model was dependent on BAFF-R and independent of TACI and BCMA. In a murine islet allograft model, BAFF blockade with a monoclonal antibody (in combination with rapamycin at induction) resulted in long-term survival of major histocompatibility complex–disparate islet allografts (12). In humans, BAFF has been identified by immunohistochemistry in renal transplant biopsies with acute rejection and appeared to correlate with C4d deposition (13). In a small study of long-term renal allograft recipients, the presence of BAFF-positive CD4 T cells in peripheral blood was associated with worse transplant function (14) and elevated BAFF mRNA and protein have been noted in kidneys explanted for chronic rejection, with infiltrating mononuclear cells the principle source (15). BAFF-R–positive B and T cells have also been identified in human renal allografts with chronic rejection (7). More recently, Thibault-Espitia et al. reported that patients undergoing antibody-compatible (Ac) transplantation with higher circulating soluble BAFF had a significantly greater risk of developing donor-specific antibodies (DSA) and that, in patients with stable graft function, high BAFF-R mRNA in peripheral blood mononuclear cells was associated with the development of graft dysfunction (16). Given the importance of BAFF in B-cell biology and the increasing evidence (outlined above) indicating a role in renal transplantation, we set out to assess serum BAFF levels in patients with end-stage renal failure undergoing renal transplantation and to determine if serum BAFF levels might predict risk of AMR. Here, we demonstrate that, in patients undergoing antibody-incompatible (Ai) renal transplantation, elevated serum BAFF levels at baseline (before both antibody removal/desensitization and transplantation) are associated with a heightened risk of subsequent AMR. Lower BAFF levels did not allow risk stratification. In Ac transplant recipients at lower risk of AMR, the rate of AMR in patients with the highest pretransplantation soluble BAFF was not statistically significantly different from those with lower BAFF levels. These data raise the possibility that, in patients undergoing Ai transplantation, elevated BAFF levels might allow the identification of those at greatest risk of AMR. Given the known roles of BAFF in B-cell biology and the availability of BAFF-blocking agents (17), BAFF neutralization in these individuals may be an interesting therapeutic strategy to explore and might help to determine whether BAFF plays a causative role in rejection.

Respiratory syncytial virus infection of airway epithelial cells, in vivo and in vitro, supports pulmonary antibody responses by inducing expression of the B cell differentiation factor BAFF

Abstract: Background The mechanisms regulating antibody expression within the human lung during airway infection are largely unknown. In this study, our objectives were to determine if infection with respiratory syncytial virus (RSV) upregulates expression of the B cell differentiation factors A proliferation inducing ligand (APRIL) and B cell activating factor of the TNF family (BAFF), if this is a common feature of viral airway infection, and how this is regulated in human airway epithelial cells. Methods We measured BAFF and APRIL protein expression in bronchoalveolar lavage (BAL) fluid from infants with severe RSV disease, and healthy control children, and in nasopharyngeal aspirates from preschool children with other single respiratory viral infections. We also measured mRNA expression in bronchial brushings from RSV-infected infants, and in RSV-infected paediatric primary airway epithelial cell cultures (pAEC). Beas-2B cell cultures were used to examine mechanisms regulating BAFF expression. Results BAFF protein and mRNA were elevated (in marked contrast with APRIL) in BAL and bronchial brushings, respectively, from RSV-infected infants. BAFF protein was also found in upper airway secretions from children with human metapneumovirus, H1N1, bocavirus, rhinovirus, RSV and Mycoplasma pneumoniae infection. BAFF mRNA and protein were expressed following in vitro RSV infection of both pAEC and Beas-2B cultures, with mRNA expression peaking 12-h postinfection. BAFF induction was blocked by addition of a neutralising anti-interferon-β antibody or palivizumab. Conclusions BAFF, produced through an interferon-β-dependant process, is a consistent feature of airway infection, and suggests a role for the airway epithelia in supporting protective antibody and B cell responses in the lung.

Galectin-9 ameliorates clinical severity of MRL/lpr lupus-prone mice by inducing plasma cell apoptosis independently of Tim-3.

Abstract: Galectin-9 ameliorates various murine autoimmune disease models by regulating T cells and macrophages, although it is not known what role it may have in B cells. The present experiment shows that galectin-9 ameliorates a variety of clinical symptoms, such as proteinuria, arthritis, and hematocrit in MRL/lpr lupus-prone mice. As previously reported, galectin-9 reduces the frequency of Th1, Th17, and activated CD8+ T cells. Although anti-dsDNA antibody was increased in MRL/lpr lupus-prone mice, galectin-9 suppressed anti-dsDNA antibody production, at least partly, by decreasing the number of plasma cells. Galectin-9 seemed to decrease the number of plasma cells by inducing plasma cell apoptosis, and not by suppressing BAFF production. Although about 20% of CD19−/low CD138+ plasma cells expressed Tim-3 in MRL/lpr lupus-prone mice, Tim-3 may not be directly involved in the galectin-9-induced apoptosis, because anti-Tim-3 blocking antibody did not block galectin-9-induced apoptosis. This is the first report of plasma cell apoptosis being induced by galectin-9. Collectively, it is likely that galectin-9 attenuates the clinical severity of MRL lupus-prone mice by regulating T cell function and inducing plasma cell apoptosis.

CCL19, a B cell chemokine, is related to the decrease of blood memory B cells and predicts the clinical response to rituximab in patients with rheumatoid arthritis.

Abstract: Objective Migration of B cells from peripheral blood to the synovium in patients with rheumatoid arthritis (RA) may predict clinical response to rituximab (RTX). We undertook this study to investigate whether serum levels of chemokines involved in B cell trafficking are correlated with blood levels of memory B cells or serum levels of B cell activation biomarkers before B cell depletion and whether chemokine levels predict RTX responsiveness. Methods Blood B cell subsets were analyzed by flow cytometry (CD27, IgD), and serum B cell activation biomarkers (rheumatoid factor, anti–cyclic citrullinated peptide, free light chains, IgG, IgA, IgM, and BAFF) were measured in 208 RA patients and 70 control subjects. Serum CCL19, CXCL12, and CXCL13 chemokine levels in patients and controls were determined by enzyme-linked immunosorbent assay. The first course of RTX was administered to RA patients, and the response was evaluated at week 24 according to European League Against Rheumatism (EULAR) criteria. Results were expressed as the odds ratio (OR) and 95% confidence interval (95% CI). Results Levels of all chemokines were increased in RA patients compared with controls, and levels were inversely correlated with CD27+ memory B cell frequency. CCL19 and CXCL13 levels correlated with levels of 6 serum B cell biomarkers and 4 serum B cell biomarkers, respectively. By univariate analysis, the CCL19 level was positively associated with EULAR response (OR 1.43 [95% CI 1.08–1.90], P = 0.01). By multivariate analysis, the CCL19 level was predictive of a response to RTX (OR 1.48 [95% CI 1.06–2.06], P = 0.02), but this did not persist after adjustment for autoantibody status. Conclusion CXCL13 and CCL19 reflect blood B cell disturbances and their levels correlate with those of other serum B cell biomarkers. CXCL13 and CCL19 are, therefore, surrogate measures for serum B cell biomarkers in RA. Serum CCL19 measurement is a new hallmark of the B cell–mediated RA subtype and may predict clinical response to RTX.