Serum B Lymphocyte Stimulator Research Articles

Impact of heart rate variability, a marker for cardiac health, on lupus disease activity.

BackgroundDecreased heart rate variability (HRV) is associated with adverse outcomes in cardiovascular diseases and has been observed in patients with systemic lupus erythematosus (SLE). We examined the relationship of HRV with SLE disease activity and selected cytokine pathways.MethodsFifty-three patients from the Oklahoma Lupus Cohort were evaluated at two visits each. Clinical assessments included the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), British Isles Lupus Assessment Group (BILAG) index, physician global assessment (PGA), and Safety of Estrogens in Lupus Erythematosus National Assessment-SLEDAI Flare Index. HRV was assessed with a 5-minute electrocardiogram, and the following HRV parameters were calculated: square root of the mean of the squares of differences between adjacent NN intervals (RMSSD), percentage of pairs of adjacent NN intervals differing by more than 50 milliseconds (pNN50), high-frequency power (HF power), and low frequency to high frequency (LF/HF) ratio, which reflects sympathetic/vagal balance. Plasma cytokine levels were measured with a multiplex, bead-based immunoassay. Serum B lymphocyte stimulator (BLyS) and a proliferation-inducing ligand (APRIL) were measured with an enzyme-linked immunosorbent assay. Linear regression analysis was applied.ResultsBaseline HRV (pNN50, HF power, LF/HF ratio) was inversely related to disease activity (BILAG, PGA) and flare. Changes in RMSSD between visits were inversely related to changes in SLEDAI (p = 0.007). Age, caffeine, tobacco and medication use had no impact on HRV. Plasma soluble tumor necrosis factor receptor II (sTNFRII) and monokine induced by interferon gamma (MIG) were inversely related with all baseline measures of HRV (p = 0.039 to <0.001). Plasma stem cell factor (SCF), interleukin (IL)-1 receptor antagonist (IL-1RA), and IL-15 showed similar inverse relationships with baseline HRV, and weaker trends were observed for interferon (IFN)-α, interferon gamma-induced protein (IP)-10, and serum BLyS. Changes in the LF/HF ratio between visits were also associated with changes in sTNFRII (p = 0.021), MIG (p = 0.003), IFN-α (p = 0.012), SCF (p = 0.001), IL-1RA (p = 0.023), and IL-15 (p = 0.010). On the basis of multivariate linear regression, MIG was an independent predictor of baseline HRV after adjusting for plasma IL-1RA, SCF, IFN-α, IP-10, and serum BLyS. In a similar model, the sTNFRII impact remained significant after adjusting for the same variables.ConclusionsImpaired HRV, particularly the LF/HF ratio, is associated with lupus disease activity and several cytokines related to IFN type II and TNF pathways. The strongest association was with MIG and sTNFRII, expanding previous immune connections of vagal signaling.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-016-1087-x) contains supplementary material, which is available to authorized users.

Serum elevation of B lymphocyte stimulator does not increase regulatory B cells in glioblastoma patients undergoing immunotherapy.

Regulatory B cells that secrete IL-10 (IL-10(+) Bregs) represent a suppressive subset of the B cell compartment with prominent anti-inflammatory capacity, capable of suppressing cellular and humoral responses to cancer and vaccines. B lymphocyte stimulator (BLyS) is a key regulatory molecule in IL-10(+) Breg biology with tightly controlled serum levels. However, BLyS levels can be drastically altered upon chemotherapeutic intervention. We have previously shown that serum BLyS levels are elevated, and directly associated, with increased antigen-specific antibody titers in patients with glioblastoma (GBM) undergoing lymphodepletive temozolomide chemotherapy and vaccination. In this study, we examined corresponding IL-10(+) Breg responses within this patient population and demonstrate that the IL-10(+) Breg compartment remains constant before and after administration of the vaccine, despite elevated BLyS levels in circulation. IL-10(+) Breg frequencies were not associated with serum BLyS levels, and ex vivo stimulation with a physiologically relevant concentration of BLyS did not increase IL-10(+) Breg frequency. However, BLyS stimulation did increase the frequency of the overall B cell compartment and promoted B cell proliferation upon B cell receptor engagement. Therefore, using BLyS as an adjuvant with therapeutic peptide vaccination could promote humoral immunity with no increase in immunosuppressive IL-10(+) Bregs. These results have implications for modulating humoral responses in human peptide vaccine trials in patients with GBM.

Evaluation of B lymphocyte stimulator and a proliferation inducing ligand as candidate biomarkers in lupus nephritis based on clinical and histopathological outcome following induction therapy

ObjectivesLupus nephritis (LN) is a major cause of morbidity in patients with systemic lupus erythematosus (SLE). B cells have a central role in the pathogenesis of SLE. B lymphocyte stimulator...

Interferon regulatory factor-5 deficiency ameliorates disease severity in the MRL/lpr mouse model of lupus in the absence of a mutation in DOCK2.

Interferon regulatory factor 5 (IRF5) polymorphisms are strongly associated with an increased risk of developing the autoimmune disease systemic lupus erythematosus. In mouse lupus models, IRF5-deficiency was shown to reduce disease severity consistent with an important role for IRF5 in disease pathogenesis. However these mouse studies were confounded by the recent demonstration that the IRF5 knockout mouse line contained a loss-of-function mutation in the dedicator of cytokinesis 2 (DOCK2) gene. As DOCK2 regulates lymphocyte trafficking and Toll-like receptor signaling, this raised the possibility that some of the protective effects attributed to IRF5 deficiency in the mouse lupus models may instead have been due to DOCK2 deficiency. We have therefore here evaluated the effect of IRF5-deficiency in the MRL/lpr mouse lupus model in the absence of the DOCK2 mutation. We find that IRF5-deficient (IRF5−/−) MRL/lpr mice develop much less severe disease than their IRF5-sufficient (IRF5+/+) littermates. Despite markedly lower serum levels of anti-nuclear autoantibodies and reduced total splenocyte and CD4+ T cell numbers, IRF5−/− MRL/lpr mice have similar numbers of all splenic B cell subsets compared to IRF5+/+ MRL/lpr mice, suggesting that IRF5 is not involved in B cell development up to the mature B cell stage. However, IRF5−/− MRL/lpr mice have greatly reduced numbers of spleen plasmablasts and bone marrow plasma cells. Serum levels of B lymphocyte stimulator (BLyS) were markedly elevated in the MRL/lpr mice but no effect of IRF5 on serum BLyS levels was seen. Overall our data demonstrate that IRF5 contributes to disease pathogenesis in the MRL/lpr lupus model and that this is due, at least in part, to the role of IRF5 in plasma cell formation. Our data also suggest that combined therapy targeting both IRF5 and BLyS might be a particularly effective therapeutic approach in lupus.

B Lymphocyte Stimulator (BLyS) is expressed in human adipocytes in vivo and is related to obesity but not to insulin resistance.

Inflammation and metabolism have been shown to be evolutionary linked and increasing evidence exists that pro-inflammatory factors are involved in the pathogenesis of obesity and type 2 diabetes. Until now, most data suggest that within adipose tissue these factors are secreted by cells of the innate immune system, e. g. macrophages. In the present study we demonstrate that B lymphocyte stimulator (BLyS) is increased in human obesity. In contrast to several pro-inflammatory factors, we found the source of BLyS in human adipose tissue to be the adipocytes rather than immune cells. In grade 3 obese human subjects, expression of BLyS in vivo in adipose tissue is significantly increased (p<0.001). Furthermore, BLyS serum levels are elevated in grade 3 human obesity (862.5+222.0 pg/ml vs. 543.7+60.7 pg/ml in lean controls, p<0.001) and are positively correlated to the BMI (r = 0.43, p<0.0002). In the present study, bariatric surgery significantly altered serum BLyS concentrations. In contrast, weight loss due to a very-low-calorie-formula-diet (800 kcal/d) had no such effect. To examine metabolic activity of BLyS, in a translational research approach, insulin sensitivity was measured in human subjects in vivo before and after treatment with the human recombinant anti-BLyS antibody belimumab. Since BLyS is known to promote B-cell proliferation and immunoglobulin secretion, the present data suggest that adipocytes of grade 3 obese human subjects are able to activate the adaptive immune system, suggesting that in metabolic inflammation in humans both, innate and adaptive immunity, are of pathophysiological relevance.

Serum BLyS and APRIL as possible indicators of disease activity in pediatric systemic lupus erythematosus and juvenile idiopathic arthritis

Aim of the workTo assess serum levels of B lymphocyte stimulator (BLyS) and a proliferation-inducing ligand (APRIL) to determine their correlations with disease activity in pediatric systemic lupus erythematosus (pSLE) and juvenile idiopathic arthritis (JIA) patients. Patients and methodsTwenty-nine pSLE patients and 33 JIA patients were recruited. SLE disease activity was assessed using the systemic lupus erythematosus disease activity index (SLEDAI), while the juvenile arthritis 27 joint disease activity score (JADAS-27) was calculated for JIA patients. Serum samples were assayed for BLyS and APRIL by the enzyme linked immunosorbent assay (ELISA). ResultsSerum BLyS and APRIL were elevated in both pSLE and JIA patients compared to controls. Serum BLyS levels correlated with both SLE and JIA disease activity (p=0.042, p=0.019, respectively) whereas serum APRIL levels correlated positively with JADAS-27 and inversely with SLEDAI (p=0.001, p=0.02, respectively). Elevated serum BLyS and APRIL were significantly associated with a lower incidence of nephritis (p=0.043, p=0.016, respectively), while elevated serum APRIL significantly associated with negative anti-dsDNA in pSLE patients (p=0.017). In JIA patients, both serum BLyS and APRIL were significantly associated with the presence of ANA (p=0.008, p<0.001, respectively), while high serum APRIL associated with the presence of RF (p=0.035). APRIL and BLYS levels correlated with each other positively in JIA but inversely in pSLE patients. ConclusionSerum BLyS showed elevated levels that correlated significantly with pSLE and JIA disease activity, accordingly anti-BLyS therapy might be of great benefit to offset disease flare. The inverse correlations observed between APRIL with both BLyS and disease activity in pSLE patients raises the possibility of being a down regulator of the disease process.

SAT0205 Blys up-regulation and salivary clonal B-cell expansion characterize sjögren’s syndrome-related lymphoproliferative disorders and correlate with the new ESSDAI score

BackgroundPrimary Sjögren’s syndrome (SS) is characterized by an increased risk of lymphoma in patients with prelymphomatous manifestations (i.e., myoepithelial sialadenitis (MESA) or mixed cryoglobulinemia). Increased levels of B-lymphocyte stimulator (BLyS)...

BLyS levels correlate with vaccine-induced antibody titers in patients with glioblastoma lymphodepleted by therapeutic temozolomide

B lymphocyte stimulator (BLyS) is a cytokine involved in differentiation and survival of follicular B cells along with humoral response potentiation. Lymphopenia is known to precipitate dramatic elevation in serum BLyS; however, the use of this effect to enhance humoral responses following vaccination has not been evaluated. We evaluated BLyS serum levels and antigen-specific antibody titers in 8 patients undergoing therapeutic temozolomide (TMZ)-induced lymphopenia, with concomitant vaccine against a tumor-specific mutation in the epidermal growth factor receptor (EGFRvIII). Our studies demonstrate that TMZ-induced lymphopenia corresponded with spikes in serum BLyS that directly preceded the induction of anti-EGFRvIII antigen-specific antibody titers, in some cases as high as 1:2,000,000. Our data are the first clinical observation of BLyS serum elevation and greatly enhanced humoral immune responses as a consequence of chemotherapy-induced lymphopenia. These observations should be considered for the development of future vaccination strategies in the setting of malignancy.

BlyS: a potential hallmark of multiple myeloma

Multiple myeloma (MM) is a plasma cell dyscrasia characterized by bone lesions and production of a paraprotein. B-lymphocyte stimulator (BLyS) and its receptor (BAFFR) were highly expressed on peripheral blood and bone marrow B cells in MM patients as compared to those with monoclonal gammopathy of unknown significance (MGUS) and healthy donors. Serum BLyS levels in MM patients were significantly higher than those in MGUS patients and healthy controls. BLyS expression was increased in bone marrow specimens from MM patients as ascertained by immunofluorescence. Furthermore, BLyS, together with IL-2 and IL-6, significantly promoted MM cell proliferation and BLyS receptor expression compared with that in the control group. Treatment with bortezomib, a therapeutic proteasome inhibitor induced apoptosis and repressed the proliferation of RPMI8226 and U266 cells through inhibition of NF-κB p65 and IκBα. These findings suggest that BLyS is involved in the immunopathogenesis of MM and may prove to be a hallmark of MM.

BLyS upregulation in Sjogren's syndrome associated with lymphoproliferative disorders, higher ESSDAI score and B-cell clonal expansion in the salivary glands

Primary SS is characterized by an increased risk of lymphoma in patients with prelymphomatous manifestations (i.e. myoepithelial sialadenitis or mixed cryoglobulinaemia). Serum B-lymphocyte stimulator (s-BLyS) levels in SS-related B-cell lymphoproliferative disorders were studied by integrating the results with the disease activity score and with molecular analyses of B-cell expansion in the salivary glands. Seventy-six primary SS patients (with or without lymphoma or prelymphomatous manifestations), 56 HCV-related cryoglobulinaemic vasculitis patients and 55 controls were studied. s-BLyS and molecular analyses of B-cell expansion in the salivary gland tissues were performed. Patients with SS and persistent parotid swelling underwent parotid biopsy. s-BLyS differed between SS subgroups, higher levels being documented in patients with lymphoma or prelymphomatous manifestations vs SS without [1.85 (0.45-4.12) ng/ml vs 1.12 (0.56-1.98) ng/ml; P < 0.0001]. s-BLyS levels significantly correlated with the European League Against Rheumatism (EULAR) SS disease activity index (r = 0.62, P < 0.0001, Spearman's test). Clonal B-cell expansion in the salivary glands, but not polyclonal B-cell expansion, was associated with higher s-BLyS levels [1.98 (0.45-4.12) ng/ml vs 1.15 (0.56-3.25) ng/ml; P = 0.013)]. Higher s-BLyS levels and tissue clonal B-cell expansion characterize SS with B-cell lymphoproliferative disorders, even at prelymphomatous stages. This subgroup of SS patients showed the highest EULAR SS disease activity index scores. This represents a biologic rationale for targeting both clonal B-cell expansion and s-BLyS overproduction in SS.

ANCA-stimulated neutrophils release BLyS and promote B cell survival: a clinically relevant cellular process

ObjectivesTo determine a role for antineutrophil cytoplasmic antibody (ANCA)-activated neutrophils in promoting B cell survival through the release of B lymphocyte stimulator (BLyS).MethodsNeutrophil BLyS expression was measured by flow cytometry....

Changes in B‐lymphocyte stimulator protein levels during treatment with albinterferon alfa‐2b in patients with chronic hepatitis C who have failed previous interferon therapy

The pharmacodynamics of albinterferon alfa-2b (alb-IFN), a novel recombinant protein consisting of interferon-α-2b genetically fused to human albumin, was evaluated in patients with chronic hepatitis C with a previous non-response to interferon-α-based therapy. B-lymphocyte stimulator (BLyS) is an essential in vivo regulator of B-lymphocyte homeostasis. This analysis examined the relationship between serum BLyS level and virologic response across a range of alb-IFN doses. In all, 115 patients were randomized initially to three alb-IFN treatment arms (900 and 1200 µg every two weeks [q2wk], and 1200 µg every four weeks) with weight-based ribavirin, followed by sequential enrollment in two higher dose arms (1500 and 1800 µg q2wk). Serum BLyS level was assessed by enzyme-linked immunosorbent assay. Serum BLyS levels at baseline were lower in African-Americans (P < 0.001). Significant BLyS inductions were observed at weeks 12 and 24 versus pretreatment; in general, serum BLyS levels returned to pretreatment levels following treatment completion. Induction of BLyS was greater in the highest dose group; a significant dose-response trend was observed at weeks 12 (P = 0.002) and 24 (P < 0.001), as well as a significant time trend, with further BLyS induction increases at week 24 versus 12 (P < 0.001). Week 24 BLyS level change correlated with hepatitis C virus RNA reduction (r = -0.28; P = 0.006), driven primarily by patients with BLyS increases > 400%, but did not correlate with sustained virologic response. Higher alb-IFN doses demonstrated dose-related BLyS increases, although the correlation with virologic response was modest.

Serum BLyS levels increase after rituximab as initial therapy in patients with follicular grade 1 non‐Hodgkin lymphoma

Serum B-lymphocyte stimulator (BLyS) levels are elevated in a subset of non-Hodgkin lymphoma (NHL) patients, particularly those with a family history of B-cell malignancies or a polymorphism in the BLyS gene. BLyS promotes growth of malignant B-cells and increased serum BLyS levels are associated with a poor clinical outcome. In this study, BLyS levels were measured before and after 4 weekly doses of rituximab in 30 patients with previously untreated follicular Grade 1 NHL. A significant increase was seen in the serum levels of BLyS (P = 0.0001) after rituximab therapy. The increase was independent of genetic variability in the BLyS gene.

The B lymphocyte stimulator receptor–ligand system in hepatitis C virus-induced B cell clonal disorders

Objective:The study aim was to examine the B lymphocyte stimulator (BLyS) receptor–ligand system in hepatitis C virus (HCV)-induced B lymphocyte clonal disorders.Methods:94 patients with chronic HCV (including 35 with HCV+...

B cell depletion therapy in systemic lupus erythaematosus: relationships among serum B lymphocyte stimulator levels, autoantibody profile and clinical response

Objective:To assess the relationships between serum B lymphocyte stimulator (BLyS) levels, autoantibody profile and clinical response in patients with systemic lupus erythaematosus (SLE) following rituximab-based B cell depletion therapy (BCDT).Methods:A...

Primary and memory B cells occupy independent homeostatic niches (B20)

Abstract The cytokines BLyS (B lymphocyte stimulator) and APRIL (a proliferation-inducing ligand) interact with three receptors – BR3, TACI, and BCMA – to regulate peripheral B cell homeostasis. Experimental evidence indicates that the BLyS-BR3 interaction governs the size and composition of primary B cell subsets by controlling the proportion of transitional (TR) cells that complete differentiation and determining the lifespan of follicular (FO) and marginal zone (MZ) B cells. The role of the BLyS family in the regulation and maintenance of memory B cell subsets remains less understood. Accordingly, we have directly tested the role of BLyS in the maintenance of memory B cells in vivo using a neutralizing anti-BLyS antibody. Mice injected with anti-BLyS show profoundly reduced numbers of TR, FO, and MZ B cells within two weeks following treatment, as well as significantly reduced serum BLyS levels. However, for mice previously immunized with NP-CGG and injected with anti-BLyS, this treatment, while similarly reducing primary B cell pools, has no effect on NP-specific memory B cell numbers. Further, upon rechallenge, the expansion of NP specific memory B cells and serum anti-NP antibody levels are similar to controls that did not receive anti-BLyS. Together, these findings indicate that memory B cells are largely independent of BLyS availability, and therefore occupy a separate homeostatic niche from primary B cells. Supported by USPHS AI054488 to MPC and T32-AI-055428 to JEC

B-lymphocyte stimulator (BLyS) stimulates immunoglobulin production and malignant B-cell growth in Waldenström macroglobulinemia

AbstractWaldenström macroglobulinemia (WM) is a serious and frequently fatal B-cell malignancy associated with an elevated monoclonal IgM protein in the serum. Many of the mechanisms leading to this disease are not yet known. B-lymphocyte stimulator (BLyS) is a TNF family member that is critical for maintenance of normal B-cell development and homeostasis. BLyS is overexpressed in a variety of B-cell malignancies and has been shown to inhibit apoptosis in malignant B cells. It also regulates immunoglobulin secretion by normal B cells. To determine the relevance of BLyS in WM, we examined the role of BLyS in WM patient samples. Malignant B cells were found to bind soluble BLyS and variably express the receptors BAFF-R, TACI, and BCMA. We also found expression of BLyS in bone marrow specimens by immunohistochemistry and elevated serum BLyS levels in patients with WM. BLyS, alone or in combination with cytokines that induce immunoglobulin production, was found to increase IgM secretion by malignant B cells. Furthermore, BLyS was found to increase the viability and proliferation of malignant B cells from WM patients. Due to the role of BLyS in WM, strategies to inhibit BLyS may potentially have therapeutic efficacy in these patients.

Elevated Serum B-Lymphocyte Stimulator Levels in Patients With Familial Lymphoproliferative Disorders

Serum B-lymphocyte stimulator (BLyS) levels have been found to be elevated in a number of immune disease models. Therefore, we sought to establish whether BLyS levels were elevated in patients with B-cell lymphoproliferative disorders and to determine whether elevated BLyS levels correlated with clinical characteristics of the disease. Specimens were collected from the peripheral blood of individuals diagnosed with B-cell chronic lymphocytic leukemia (B-CLL; n = 70) or from age- and sex-matched patients seen at the same institution (n = 41). Serum BLyS levels were determined by enzyme-linked immunosorbent assay, and sequencing of the BLyS promoter was performed by conventional methods and confirmed by restriction fragment length polymorphism analysis. We found that elevated BLyS levels were more common in patients with familial B-CLL than individuals with sporadic B-CLL or normal controls. Because of this association, we sequenced the BLyS promoter in patients with B-CLL and normal controls and identified a polymorphic site, -871 C/T. We found that the wild-type sequence was significantly underrepresented in patients with familial B-CLL (4%) compared with patients with sporadic B-CLL (30%; P = .01) or controls (24%; P = .04). Furthermore, using a luciferase reporter under control of the BLyS promoter containing either a C or a T at position -871, we found that the reporter construct containing a T at -871 had a 2.6-fold increase in activity (P = .004). Our data suggest serum BLyS levels are elevated in patients with familial B-CLL and that elevated BLyS levels correlate with the presence of a T at -871 in the BLyS promoter.

Role of B-Lymphocyte Stimulator (BLyS) in Waldenstrom's Macroglobulinemia.

Waldenstrom's macroglobulinemia (WM) is a serious and frequently fatal disorder characterized by the production of a monoclonal IgM protein, a lymphoplasmacytic infiltrate in the bone marrow, and associated symptoms including anemia, lymphadenopathy and hyperviscosity. Many of the mechanisms leading to this disease are not yet known. It is clear, however, that there is dysregulation of the balance between cell proliferation and programmed cell death. BLyS (B-lymphocyte stimulator) is a TNF family member expressed by monocytes, neutrophils, macrophages, and dendritic cells. BLyS has been shown to be critical for maintenance of normal B cell development and homeostasis, and has been found to stimulate lymphocyte growth. BLyS is overexpressed in a variety of B-cell malignancies and has been shown to inhibit apoptosis in malignant B-cells. Studies of the effects of BLyS on B cell physiology have shown that it also regulates immunoglobulin secretion. In previous work, we have shown that malignant B cells from patients with WM are able to bind soluble BLyS and variably express the BLyS receptors, BAFF-R, TACI and BCMA. We also found expression of BLyS in bone marrow specimens by immunohistochemistry and elevated serum BLyS levels in patients with WM. The goal of this study was to determine the functional role of BLyS-receptor ligand system in Waldenstrom's macroglobulinemia and its relevance to the increased immunoglobulin production seen in this disease. Using cells from WM patients, we first examined the ability of BLyS to increase the secretion of IgM by malignant B cells. BLyS, alone or in combination with cytokines that induce plasmacytic differentiation and immunoglobulin production (IL-2, IL-6, IL-10 and IL-12), was found to increase IgM secretion by malignant B cells. Mean baseline IgM levels significantly increased in cells treated with BLyS (p=0.03), cytokines (p=0.0002) and a combination of BLyS and cytokines (p<0.0001). We then determined the effect of BLyS on the survival of malignant B cells using Annexin-V/PI staining. Compared to cells cultured in media alone, BLyS was found to increase viability of malignant B cells from WM patients. Cell viability was normalized relative to the media-alone control and the median relative viability increased significantly compared to controls (median increase 41.2%; range 8 – 46%). Next, we examined the ability of BLyS to modulate cell proliferation using thymidine incorporation. Using WM patient samples, BLyS was found to significantly enhance the proliferation of malignant B cells (p=0.0002). Furthermore, addition of anti-Ig antibody further enhanced the ability of BLyS to promote the proliferation of malignant B cells (p<0.0001). In summary, we have demonstrated that BLyS enhances IgM secretion by malignant B cells from patients with Waldenstrom's macroglobulinemia. We have also demonstrated the ability of BLyS to enhance the survival and proliferation of malignant B cells. Strategies to inhibit BLyS may potentially have therapeutic efficacy in Waldenstrom's macroglobulinemia.

B-Lymphocyte Stimulator (BLyS) Is Highly Expressed in Waldenstrom's Macroglobulinemia.

Waldenstrom's macroglobulinemia is a serious and frequently fatal illness, however many of the mechanisms leading to this disease are not yet known. It is clear, however, that there is dysregulation of the balance between cell proliferation and programmed cell death. BLyS (B-lymphocyte stimulator) is a newly identified TNF family member expressed by monocytes, macrophages, and dendritic cells. BLyS has been shown to be critical for maintenance of normal B cell development and homeostasis, and has been found to stimulate lymphocyte growth. BLyS is overexpressed in a variety of B-cell malignancies and has been shown to inhibit apoptosis in malignant B-cells. Studies of the effects of BLyS on B cell physiology have shown that it also regulates immunoglobulin secretion.To determine the relevance of the BLyS receptor-ligand system in Waldenstrom's macroglobulinemia, we examined malignant B cells from 5 patients with Waldenstrom's macroglobulinemia for their ability to bind soluble BLyS and for the expression of the known BLyS receptors, TACI, BAFF-R, or BCMA. The malignant B cells were found to bind BLyS and express BAFF-R and TACI. BCMA expression was undetectable. We then determined the expression of BLyS in bone marrow specimens from 5 patients with Waldenstrom's macroglobulinemia by immunohistochemistry and compared it to the expression in 5 normal bone marrow specimens. The lymphoplasmacytic cell infiltrate in the bone marrow of patients with Waldenstrom's macroglobulinemia showed significantly increased BLyS expression. We further determined the serum BLyS levels by ELISA in stored serum specimens from patients with Waldenstrom's macroglobulinemia (n=20), and compared them to serum BLyS levels in other patients with lymphoplasmacytic lymphoma without elevated immunoglobulin levels (n=10) and to serum levels in normal controls (n=50). Serum BLyS levels in Waldenstrom's patients (mean: 49.6ng/ml) as well as those in patients with lymphoplasmacytic lymphoma (mean; 46.7ng/ml) were significantly higher than normal controls (mean 12.6ng/ml).In conclusion, we have demonstrated that malignant B cells from patients with Waldenstrom's macroglobulinemia express the receptors for BLyS and can bind soluble BLyS. Furthermore, we have found that serum BLyS levels are significantly elevated in patients with Waldenstrom's macroglobulinemia when compared to controls. Strategies to inhibit BLyS may potentially have significant therapeutic efficacy in Waldenstrom's macroglobulinemia.