Contributions of each of the BAFF receptors to the lymphocyte profiles in C57BL/6 mice.

BAFF, a vital B cell survival and differentiation factor, has three receptors: B-cell maturation antigen (BCMA), transmembrane activator and CAML interactor (TACI) and BR3. Although B cells are greatly reduced in B6.Baff-/- (which harbour no BAFF) and B6.Br3-/- mice (which harbour supra-normal levels of BAFF), the distributions of B cell subsets and relationships between Foxp3+ and CD4+ cells in these mice differ. Using a large panel of B6 congenic knockout and/or transgenic mice, we demonstrate that (1) supra-normal levels of BAFF per se do not explain the phenotypic differences between B6.Baff-/- and B6.Br3-/- mice; (2) B cells are expanded in B6.Taci-/- mice, with preferential expansion of follicular (FO) B cells at the expense of CD19+CD21-/loCD23-/lo B cells but without the preferential expansion of Foxp3+ cells observed in B6 mice bearing a Baff transgene; (3) despite no expansion in total B cells, percentages of FO B cells and marginal zone B cells are higher and percentages of CD19+CD21-/loCD23-/lo B cells are lower in young B6.Bcma-/- mice, consistent with the inability of B6.Br3-/-.Taci-/- mice to recapitulate the B cell profile of B6.Baff-/- mice; and (4) percentages of Foxp3+ cells in B6.Br3-/-.Taci-/- mice are intermediate between those in B6.Br3-/- and B6.Taci-/- mice despite the B cell profile of B6.Br3-/-.Taci-/- mice strongly resembling that of B6.Br3-/- mice. Collectively, our findings point to a non-redundant role for each of the BAFF receptors in determining the ultimate lymphocyte profile of the host. This may have clinically relevant ramifications in that the degree that a candidate therapeutic agent blocks engagement of any given individual BAFF receptor may affect its clinical utility.

BAFF-R and TACI expression on CD3+ T cells: Interplay among BAFF, APRIL and T helper cytokines profile in systemic lupus erythematosus.

BACKGROUND: Systemic lupus erythematosus (SLE) is the prototype of systemic autoimmune disease, characterized by loss of immune tolerance against self-antigens where autoantibody production is the hallmark of disease. B-cell-activating factor (BAFF) and A proliferation-inducing ligand (APRIL) are cytokines that promote autoreactive cell survival, immunoglobulin-class switching and autoantibody responses in human and mouse SLE models. BAFF and APRIL exert their functions through interactions with their receptors BAFF-R and TACI that are differentially expressed in B lymphocyte subsets, monocytes, dendritic cells and T lymphocytes. BAFF stimulation favors T lymphocyte activation and cytokine production through BAFF-R, which could contribute to the Th1, Th17 and/or Th2 response dysregulation observed in SLE patients. OBJECTIVE: To evaluate the expression of the cytokines BAFF and APRIL and their association with the receptors BAFF-R and TACI on CD3+ T cells and to evaluate Th1/Th2/Th17 cytokine profile in patients with SLE. METHODS: Fifteen healthy controls (HC) and 36 SLE patients were included, and their demographic and clinical data were assessed. The disease activity index (Mex-SLEDAI) and damage index (SLICC) were applied to the SLE patients. BAFF-R and TACI expression on CD3+ T cells were evaluated by flow cytometry. Serum BAFF and APRIL concentrations were measured by enzyme-linked immunosorbent assays (ELISA). Cytokine levels of Th1 (IL-12, IL-2, IFN-γ, TNF-α), Th2 (IL-4, IL-6, IL-10, IL-13) and Th17 (IL-1ß e IL-17) were quantified with a multiplex assay (MAGPIX). Statistical analysis was performed using PASW Statistics v.20 and GraphPad Prism v.6 software. RESULTS: No differences in BAFF-R or TACI expression on the CD3+ T cells of SLE and HC were observed. BAFF-R expression correlates inversely with disease activity (r = -0.538, p < 0.01), while TACI correlates with disease activity (r = 0.530, p < 0.05). Serum BAFF and APRIL levels were high in SLE patients and correlated with the disease activity index Mex-SLEDAI (r = 0.621, p < 0.01 and r = 0.416, p < 0.05). SLE patients were found to have significantly higher levels of IL-12, IFN-γ, TNF-α, IL-6, IL-10, IL-13, IL-1ß and IL-17 compared to HC (p < 0.05). Cytokines IL-17 (r = 0.526) and TNF-α (r = 0.410) correlate with disease activity (p < 0.05), while APRIL (r = 0.477), IL-10 (r = 0.426) and IFN-γ (r = 0.440) levels were associated with organ damage (p < 0.01). Serum BAFF expression levels correlate with IL-4 (r = 0.424; p < 0.05), IL-6 (r = 0.420; p < 0.05) and IL-10 (r = 0.459; p < 0.01), whereas APRIL levels correlate with IL-2 (r = 0.666; p < 0.01), IL-12 (r = 0.611; p < 0.01) and TNF-α (r = 0.471; p < 0.05) cytokines. A subgroup of SLE patients with high serum BAFF levels (>2 ng/mL) also showed increased APRIL, IL-2, IL-6 and IL-10 levels (p < 0.05). Finally, BAFF, IL-4 and TNF-α serum levels were associated with high titers of antinuclear antibodies. CONCLUSIONS: The study demonstrates an imbalance in the Th1/Th2 cytokine profile, with increased proinflammatory cytokines, as well as BAFF and APRIL serum levels. Associations of BAFF with Th2 profile cytokines and disease activity, as well as APRIL with Th1 profile cytokines and organ damage, suggest that BAFF and APRIL generated in the autoimmunity context could through still unknown mechanisms, modulate the microenvironment, and perpetuate the inflammatory response, autoantibody production and organ damage observed in SLE patients.

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.

The BAFF / APRIL axis plays an important role in virus-induced peritoneal responses in rainbow trout.

IgM+ B cells have been recently demonstrated to be key regulators of peritoneal inflammation in teleost, as a large number of them occupy the peritoneal cavity after 48 h of antigenic stimulation. Despite this, the number of studies addressing the mechanism through which this cell population expands and differentiates in response to stimuli has been scarcely addressed. Because the BAFF/APRIL axis is known to play a major role in B cell survival and differentiation in mammals, we hypothesized that it could be affected in the peritoneal cavity in response to an inflammatory stimulus. To verify this hypothesis, we studied how BAFF, APRIL and the fish-specific related cytokine BALM as well as their putative receptors are regulated in rainbow trout after intraperitoneal (i.p.) injection of viral hemorrhagic septicemia virus (VHSV). When the transcriptional analysis was performed in total cells from the peritoneum, we observed that VHSV provoked an up-regulation of both BAFF and BAFF receptor (BAFF-R) mRNA levels. However, when we examined how isolated peritoneal IgM+ B cells were transcriptionally affected by VHSV i.p. injection, we found that APRIL, BALM and the transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) were also up-regulated in response to the virus. IgM- cells, on the other hand, only up-regulated BALM transcription in response to VHSV. Finally, to gain further insight on the role that these cytokines play in the peritoneum, we have studied their effect on the survival of peritoneal IgM+ B cells. This work demonstrates a key role for the BAFF/APRIL axis in the peritoneal inflammatory response and contributes to further understanding how IgM+ B cells are regulated at this specific peripheral site.

Association of BAFF, APRIL serum levels, BAFF-R, TACI and BCMA expression on peripheral B-cell subsets with clinical manifestations in systemic lupus erythematosus.

OBJECTIVE: B-cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL) signaling pathways regulate B-cell survival through interactions with their receptors BAFF-R, TACI and BCMA. We evaluated the association of these ligands/receptors on B-cell subsets according to clinical manifestations of systemic lupus erythematosus (SLE). METHODS: BAFF and APRIL serum concentrations were measured in 30 SLE patients by enzyme-linked immunosorbent assay. The BAFF-R, TACI and BCMA expression was analyzed on each B cell subset (CD19 + CD27-CD38-/ + naïve; CD19 + CD27 + CD38-/ + memory; CD19 + CD27-CD38 + + immature and CD19 + CD27 + CD38 + + plasma cells) by flow cytometry, and compared among patients with different clinical manifestations as well as healthy controls (HCs). RESULTS: Serum BAFF and APRIL levels were high in SLE patients and correlated with the Mex-SLEDAI disease activity index (r = 0.584; p = 0.001 and r = 0.456; p = 0.011, respectively). The SLE patients showed an increased proportion of memory and plasma B cells (p < 0.05). BAFF-R, TACI and BCMA expression in SLE patients was decreased in almost all B cell subsets compared to HCs (p < 0.05). A lower BCMA expression was associated with severe disease activity, glomerulonephritis, serositis and hemolytic anemia (p < 0.01). BCMA expression showed a negative correlation with Mex-SLEDAI score (r = -0.494, p = 0.006). CONCLUSIONS: Decreased BCMA expression on peripheral B cells according to severe disease activity suggests that BCMA plays an important regulating role in B-cell hyperactivity and immune tolerance homeostasis in SLE patients.

Significant immunomodulatory properties of curcumin in patients with osteoarthritis; a successful clinical trial in Iran.

Osteoarthritis (OA) routinely is known as a multifactorial degenerative joint disease. This trial aimed to assess the curcumin (an active element of turmeric) effects on the immune responses in OA patients. Thirty patients were selected according to the American College of Rheumatology (ACR) criteria and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and equally divided into the two groups; intervention (received Sinacurcumin® 80 mg daily) and placebo, followed for 3 months. In the intervention group, our data showed a noticeably decrease in Visual Analog Score (VAS), C-reactive protein (CRP), CD4+ and CD8+ T cells, Th17 cells and B cells frequency. Additionally, Treg cells indicated a significant increase and Treg/Th17 cells ratio showed a meaningfully shifted toward Treg lymphocytes. In conclusion, our data indicated that clinical manifestation was ameliorated considerably following the administration of curcumin. Moreover, our data demonstrated the immunomodulatory effects of curcumin in OA patients.

A significant decrease of BAFF, APRIL, and BAFF receptors following mesenchymal stem cell transplantation in patients with refractory rheumatoid arthritis.

In the present study, we aimed to evaluate effects of autologous mesenchymal stem cells (MSCs) intravenous administration on the response of B cells, BAFF, APRIL, and their receptors on the surface of B cells at 1, 6, and 12 month follow-up periods in refractory rheumatoid arthritis (RA) patients. Thirteen patients with refractory RA received autologous MSCs. Plasma levels of BAFF and APRIL were measured employing ELISA method, followed by estimating B cell population and BAFFRs evaluation by flow cytometry technique. Gene expression of BAFF, APRIL, and their receptors on B cell surface in PBMCs was evaluated by SYBR Green real-time PCR technique. Plasma concentration of BAFF significantly decreased 1 and 6 months after the MSCT (MSCs Transplantation). Plasma concentration of APRIL significantly decreased 1 month after the MSCT. Percentages of CD19 + B cells in the PBMC population significantly decreased 12 months after the MSCT. Percentages of BR3 + CD19 + B cells and BCMA + CD19 + B cells significantly decreased at the 12th month after the MSCT. The gene expression of BAFF in the PBMC population significantly decreased during 6, and 12 months after the MSCT. The gene expression of APRIL significantly decreased on month 6 after the MSCT. The gene expression of BR3 significantly decreased during 1, 6, and 12 months after the MSCT. The MSCT seems to decrease B cells response because of the reduced production of BAFF and APRIL cytokines and decrease the expression of their receptors on the surface of B cells.

Expression of BAFF and BAFF receptors in primary Sjögren's syndrome patients with ectopic germinal center-like structures.

B cell-activating factor (BAFF) is an essential cytokine in primary Sjögren's syndrome (pSS) physiopathology. It has been reported that pSS patients develop germinal center-like (GC-like) structures in their minor salivary glands (MSGs). BAFF, BAFF-R, TACI, and BCMA expression was analyzed in MSGs from 29 subjects (nonspecific chronic sialadenitis and focal lymphocytic sialadenitis with the presence [pSS-GC(+)] or absence [pSS-GC(-)] of GC-like structures). Twenty-four percent of patients showed ectopic GC-like structures and a high focus score [p < 0.001 vs pSS-GC(-)]. BAFF serum levels (sBAFF) were high in pSS patients (p = 0.025 vs healthy subjects). However, the pSS-GC(-) group showed higher sBAFF levels than pSS-GC(+) patients. BAFF and BAFF-R glandular expression levels were higher in pSS-GC(+) patients, without significant differences compared to pSS-GC(-) patients. Soluble levels of BAFF correlated with anti-La/SSB antibodies and disease duration. Our results showed that BAFF could contribute to focal lymphocytic infiltration. The role of BAFF-binding receptors in MSGs is proposed as a mechanism for the possible establishment of ectopic GC-like structures and disease progression in some patients. In conclusion, this study supports previous evidence that considers the active BAFF system role in the pathogenesis of pSS and the need for strong biomarkers in this disease.