scholarly journals Interleukin-5 (IL-5) and IL-6 define two molecularly distinct pathways of B-cell differentiation.

1993 ◽  
Vol 13 (7) ◽  
pp. 3929-3936 ◽  
Author(s):  
T D Randall ◽  
F E Lund ◽  
J W Brewer ◽  
C Aldridge ◽  
R Wall ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
B Cell Lymphoma ◽  
Receptor Expression ◽  
High Rate ◽  
B Cell Differentiation ◽  
Interleukin 5 ◽  
Stage Of Development ◽  
Differentiation Factors

Interleukin-5 (IL-5) and IL-6 have both been reported to act as B-cell differentiation factors by stimulating activated B cells to secrete antibody. However, it has not been possible to directly compare the effects of these two lymphokines because of the lack of a suitable B-cell line capable of responding to both. We have identified a clonal, inducible B-cell lymphoma, CH12, that has this property. Both IL-5 and IL-6 can independently stimulate increases in steady-state levels of immunoglobulin and J-chain mRNA and proteins, and they both induce the differentiation of CH12 into high-rate antibody-secreting cells. Nevertheless, there are significant differences in the activities of these two lymphokines. First, while IL-6 acts only as a differentiation factor, IL-5 also augments the proliferation of CH12 cells. Second, the differentiation stimulated by IL-5 but not by IL-6 is partially inhibited by IL-4. Inhibition of IL-5-induced differentiation was not at the level of IL-5 receptor expression, since IL-4 did not inhibit IL-5-induced proliferation. Third, IL-5 but not IL-6 stimulated increased mouse mammary tumor proviral gene expression in CH12 cells. These results demonstrate that while both IL-5 and IL-6 may act as differentiation factors for B cells, they induce differentiation by using at least partially distinct molecular pathways. Our results also establish that B cells characteristic of a single stage of development can independently respond to IL-4, IL-5, and IL-6.

Interleukin-5 (IL-5) and IL-6 define two molecularly distinct pathways of B-cell differentiation

1993 ◽  
Vol 13 (7) ◽  
pp. 3929-3936
Author(s):  
T D Randall ◽  
F E Lund ◽  
J W Brewer ◽  
C Aldridge ◽  
R Wall ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
B Cell Lymphoma ◽  
Receptor Expression ◽  
High Rate ◽  
B Cell Differentiation ◽  
Interleukin 5 ◽  
Stage Of Development ◽  
Differentiation Factors

Interleukin-5 (IL-5) and IL-6 have both been reported to act as B-cell differentiation factors by stimulating activated B cells to secrete antibody. However, it has not been possible to directly compare the effects of these two lymphokines because of the lack of a suitable B-cell line capable of responding to both. We have identified a clonal, inducible B-cell lymphoma, CH12, that has this property. Both IL-5 and IL-6 can independently stimulate increases in steady-state levels of immunoglobulin and J-chain mRNA and proteins, and they both induce the differentiation of CH12 into high-rate antibody-secreting cells. Nevertheless, there are significant differences in the activities of these two lymphokines. First, while IL-6 acts only as a differentiation factor, IL-5 also augments the proliferation of CH12 cells. Second, the differentiation stimulated by IL-5 but not by IL-6 is partially inhibited by IL-4. Inhibition of IL-5-induced differentiation was not at the level of IL-5 receptor expression, since IL-4 did not inhibit IL-5-induced proliferation. Third, IL-5 but not IL-6 stimulated increased mouse mammary tumor proviral gene expression in CH12 cells. These results demonstrate that while both IL-5 and IL-6 may act as differentiation factors for B cells, they induce differentiation by using at least partially distinct molecular pathways. Our results also establish that B cells characteristic of a single stage of development can independently respond to IL-4, IL-5, and IL-6.

Regulation of CCR6 chemokine receptor expression and responsiveness to macrophage inflammatory protein-3α/CCL20 in human B cells

Blood ◽  
2000 ◽  
Vol 96 (7) ◽  
pp. 2338-2345 ◽  
Author(s):  
Roman Krzysiek ◽  
Eric A. Lefevre ◽  
Jérôme Bernard ◽  
Arnaud Foussat ◽  
Pierre Galanaud ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Chemokine Receptor ◽  
Memory B Cells ◽  
Receptor Expression ◽  
B Cell Differentiation ◽  
Hematopoietic Stem ◽  
Inflammatory Protein ◽  
Macrophage Inflammatory Protein

Abstract The regulation of CCR6 (chemokine receptor 6) expression during B-cell ontogeny and antigen-driven B-cell differentiation was analyzed. None of the CD34+Lin− hematopoietic stem cell progenitors or the CD34+CD19+ (pro-B) or the CD19+CD10+ (pre-B/immature B cells) B-cell progenitors expressed CCR6. CCR6 is acquired when CD10 is lost and B-cell progeny matures, entering into the surface immunoglobulin D+ (sIgD+) mature B-cell pool. CCR6 is expressed by all bone marrow–, umbilical cord blood–, and peripheral blood–derived naive and/or memory B cells but is absent from germinal center (GC) B cells of secondary lymphoid organs. CCR6 is down-regulated after B-cell antigen receptor triggering and remains absent during differentiation into immunoglobulin-secreting plasma cells, whereas it is reacquired at the stage of post-GC memory B cells. Thus, within the B-cell compartment, CCR6 expression is restricted to functionally mature cells capable of responding to antigen challenge. In transmigration chemotactic assays, macrophage inflammatory protein (MIP)-3α/CC chemokine ligand 20 (CCL20) induced vigorous migration of B cells with differential chemotactic preference toward sIgD− memory B cells. These data suggest that restricted patterns of CCR6 expression and MIP-3α/CCL20 responsiveness are integral parts of the process of B-lineage maturation and antigen-driven B-cell differentiation.

Blimp1 Is a Tumor Suppressor Gene in Diffuse Large B Cell Lymphoma.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 446-446 ◽  
Author(s):  
Jonathan Mandelbaum ◽  
Govind Bhagat ◽  
Tongwei Mo ◽  
Alexander Tarakhovsky ◽  
Laura Pasqualucci ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
Tumor Suppressor ◽  
B Cell ◽  
Tumor Suppressor Gene ◽  
B Cell Lymphoma ◽  
Suppressor Gene ◽  
Cell Phenotype ◽  
B Cell Differentiation

Abstract Abstract 446 The PRDM1/ BLIMP1 gene encodes a zinc finger transcriptional repressor that is expressed in a subset of germinal center (GC) B cells and in all plasma cells, and is required for terminal B cell differentiation. The BLIMP1 locus is biallelically inactivated by structural alterations in approximately one third of activated B cell-like diffuse large B cell lymphoma (ABC-DLBCL) (Pasqualucci et al, J Exp Med 2006). Moreover, the expression of the Blimp1 protein is absent in up to 80% of ABC-DLBCL due to alternative genetic and epigenetic mechanisms. These findings suggest that BLIMP1 may function as a tumor suppressor gene whose loss may contribute to the pathogenesis of this lymphoma type by blocking terminal B cell differentiation. To investigate the role of BLIMP1 inactivation in lymphomagenesis in vivo, we tested whether conditional deletion of the Blimp1 gene in mouse B cells can promote the growth of lymphomas recapitulating the features of ABC-DLBCL. Toward this end, a mouse model carrying a loxP-flanked exon 5 of the Blimp1 gene that can be deleted by Cre-mediated recombination (Ohinata et al, Nature 2005) was crossed with a CD19-Cre deletor strain, expressing the Cre recombinase in all B cells. The resulting mice were monitored for tumor development and survival. Consistent with previous observations in a similar model (Shapiro-Shelef et al, Immunity 2003), Blimp1 conditional knockout (Blimp1CD19KO) mice showed a severe impairment in the generation of CD138+ plasma cells and had decreased serum immunoglobulin levels of all isotypes, together with a two-fold increase in the number of PNAhiCD95+ GC B cells. Over time, significantly reduced survival was observed in the Blimp1CD19KO cohort, with only 27% of the animals being alive at 15 months of age (LogRank p value<0.0001). Macroscopic and flow cytometric analysis of the lymphoid compartments revealed the presence of splenomegaly in 32/38 (84%) Blimp1CD19KO, as compared to 1/25 (4%) age-matched wildtype (WT) littermates, and a significant increase in IgM+IgD-CD21+CD23lo splenic B cells, indicative of marginal zone B cell expansion. In addition, 79% (n=30/38) of Blimp1CD19KO mice showed markedly hyperplastic bronchus-associated lymphoid tissue (BALT). Notably, between 10 and 16 months of age 34% (13/38) of these animals developed clonal lymphoproliferative disorders with a mature B cell phenotype (B220+Pax5+) and histologic features of DLBCL (n=6) or less aggressive lymphoid proliferations (LPD: n=6; marginal zone lymphoma: n=1), in contrast with 1/27 heterozygous and 0/25 WT animals. Sequencing analysis of the rearranged immunoglobulin variable region genes in lymphoma biopsies revealed the presence of somatic mutations in 6/8 samples investigated, demonstrating their origin from a GC-experienced B cell. Moreover, immunohistochemical staining for Bcl6 and Irf4 documented a late-GC “activated” B cell phenotype (Bcl6-Irf4+) in all tumors tested (n=4), consistent with the expansion of cells that had been committed to plasma cell differentiation. These data demonstrate that Blimp1 is a bona-fide tumor suppressor gene whose B-cell specific inactivation in vivo promotes the development of lymphomas sharing features of the human ABC-DLBCL. Disclosures: No relevant conflicts of interest to declare.

Human clones with natural killer function can activate B cells and secrete B cell differentiation factors

1985 ◽  
Vol 15 (6) ◽  
pp. 606-610 ◽  
Author(s):  
Anna Vyakarnam ◽  
Malcolm K. Brenner ◽  
Joyce E. Reittie ◽  
Clare H. Houker ◽  
Peter J. Lachmann
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Natural Killer ◽  
B Cell Differentiation ◽  
Differentiation Factors

scholarly journals Patterns of microRNA expression characterize stages of human B-cell differentiation

Blood ◽  
2009 ◽  
Vol 113 (19) ◽  
pp. 4586-4594 ◽  
Author(s):  
Jenny Zhang ◽  
Dereje D. Jima ◽  
Cassandra Jacobs ◽  
Randy Fischer ◽  
Eva Gottwein ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
B Cell Lymphoma ◽  
Microrna Expression ◽  
Lymphocytic Leukemia ◽  
Cell Phenotype ◽  
Tumor Type ◽  
B Cell Differentiation ◽  
B Cell Malignancies

Abstract Mature B-cell differentiation provides an important mechanism for the acquisition of adaptive immunity. Malignancies derived from mature B cells constitute the majority of leukemias and lymphomas. These malignancies often maintain the characteristics of the normal B cells that they are derived from, a feature that is frequently used in their diagnosis. The role of microRNAs in mature B cells is largely unknown. Through concomitant microRNA and mRNA profiling, we demonstrate a potential regulatory role for microRNAs at every stage of the mature B-cell differentiation process. In addition, we have experimentally identified a direct role for the microRNA regulation of key transcription factors in B-cell differentiation: LMO2 and PRDM1 (Blimp1). We also profiled the microRNA of B-cell tumors derived from diffuse large B-cell lymphoma, Burkitt lymphoma, and chronic lymphocytic leukemia. We found that, in contrast to many other malignancies, common B-cell malignancies do not down-regulate microRNA expression. Although these tumors could be distinguished from each other with use of microRNA expression, each tumor type maintained the expression of the lineage-specific microRNAs. Expression of these lineage-specific microRNAs could correctly predict the lineage of B-cell malignancies in more than 95% of the cases. Thus, our data demonstrate that microRNAs may be important in maintaining the mature B-cell phenotype in normal and malignant B cells.

scholarly journals G protein subunit G alpha 16 expression is restricted to progenitor B cells during human B-cell differentiation

Blood ◽  
1995 ◽  
Vol 85 (7) ◽  
pp. 1836-1842 ◽  
Author(s):  
MY Mapara ◽  
K Bommert ◽  
RC Bargou ◽  
C Leng ◽  
C Beck ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Cell Line ◽  
Cell Lines ◽  
B Cell Lymphoma ◽  
Cell Phenotype ◽  
Low Grade ◽  
B Cell Differentiation ◽  
Human B Cell

Recently G alpha 16, a new guanosine triphosphate (GTP) binding protein alpha subunit has been described to be specifically expressed in human hematopoietic cells. Expression of G alpha 16 was observed in human cell lines of myelomonocytic and T-lymphocytic origin, but not in human B-cell lines Raji and IM9. We studied the expression of G alpha 16 in human B cells corresponding to different stages of B-cell differentiation by means of reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting. The human Burkitt's lymphoma cell lines Raji, Ramos, BJAB, the lymphoblastoid cell line SKW6.4, and the plasmocytoma cell line U266 were devoid of G alpha 16. In contrast, G alpha 16 was detected in the human progenitor B cell lines Reh and Nalm-6. Using the mu+, k-cell line BLIN-1 (pre-B cell phenotype) and its derived subclone 1E8 (surface mu+, k+; B-cell phenotype) G alpha 16 expression was found to disappear on transition from pre-B to B-cell differentiation stage. The analysis of a broad panel of human neoplastic B lymphocytes ranging from progenitor B-acute lymphatic leukemia (pre-pre-B-ALL), common acute leukemias (cALL), pre-B-ALL, mature B-ALL to low grade B-cell lymphoma (chronic lymphocytic leukemia of B-cell type, leukemic centrocytic non-Hodgkins lymphoma [NHL], hairy cell leukemia) showed that G alpha 16 expression is limited to progenitor and pre-B-ALL cells. Therefore, we conclude that within B-cell differentiation, G alpha 16 is expressed solely during early B cell ontogeny and downregulated during differentiation. Thus, G alpha 16 might be an important regulator involved in signaling processes in progenitor B cells.

Aberrant Co-Expression of Key Transcription Factors BCL6, IRF4 and FOXP1 Are Frequently Observed in Diffuse Large B-Cell Lymphoma

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3761-3761
Author(s):  
Maayke Boll ◽  
Sharon L Barrans ◽  
Charles S McManamy ◽  
Andrew S Jack
Keyword(s):  
Transcription Factors ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Germinal Centre ◽  
B Cell Differentiation ◽  
Large B Cell Lymphoma ◽  
Large B Cell

Abstract Diffuse Large B-cell Lymphoma (DLBCL) is classified into germinal centre (GCB) and activated B-cell (ABC) type by comparison with the phenotype of normal B-cells. Using single-color immunocytochemistry, tumors can be classified using a simple algorithm based on the expression of CD10, BCL6 and IRF4. This classification may have prognostic relevance and correlates with balanced translocations involving the immunoglobulin locus. However, the phenotypic differences between normal and neoplastic cells may be of greater relevance to understanding the pathogenesis of DLBCL and in developing effective diagnostic techniques. To investigate this we examined the co-expression of BCL6, IRF4 and FOXP1. These are key transcription factors that regulate the process of germinal centre and post germinal centre B-cell differentiation. Abnormal co-expression of these molecules would be expected to have major effects on the overall cellular phenotype. A multi-color immunofluorescence (MCIF) technique was developed that allowed the co-expression of these markers to be assessed in relation to the PAX5 positive B-cell population. The use of a multi-color technique allows the distinction between co-expression at the level of individual cells and differentiation within the tumor as a whole. We first determined the pattern of expression of these transcription factors in normal B-cells. In reactive lymph nodes the expression of BCL6, IRF4 and FOXP1 was almost mutually exclusive with only a small proportion of co-expressing cells. In a series of 61 DLBCL co-expression of both BCL6/IRF4 and IRF4/FOXP1 was found in 41/61 (67%) of the cases. In most of these cases the level of co-expression was greater than 50% of the PAX5 positive large lymphoid cells. Co-expression was not present in 11/61 (18%) of the tumors. In the remaining cases there was co-expression of either BCL6/IRF4 or IRF4/FOXP1. There was no correlation between the occurrence of co-expression of these combinations of transcription factors and the expression of CD10 or the classification into GCB and ABC phenotypes. In 16 of the cases the sample used was a small needle core biopsy in which assessment of nodal architecture was impossible. In these cases it was possible to confidently determine the presence of abnormal co-expression in 14/16 (87.5%) of the cases. One explanation for the aberrant co-expression of BCL6 and IRF4 in DLBCL would be the presence of a 3q27 rearrangement leading to dysregulation of BCL6 expression. However, in this series there was no correlation between BCL6/IRF4 co-expression and abnormalities of 3q27 detected by interphase FISH. These results show that in the majority of cases of DLBCL the key transcription factors regulating post germinal centre B-cell differentiation are expressed in combinations not seen in normal B-cells. This is likely to be a central element in the pathogenesis of these tumors. The ability to reliably identify these abnormalities by MCIF has potential value in improving the reliability of diagnosis of DLBCL when only small biopsy samples are available and it is likely that this approach can be extended to other types of lymphoma.

Regulation of CCR6 chemokine receptor expression and responsiveness to macrophage inflammatory protein-3α/CCL20 in human B cells

Blood ◽  
2000 ◽  
Vol 96 (7) ◽  
pp. 2338-2345 ◽  
Author(s):  
Roman Krzysiek ◽  
Eric A. Lefevre ◽  
Jérôme Bernard ◽  
Arnaud Foussat ◽  
Pierre Galanaud ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Chemokine Receptor ◽  
Memory B Cells ◽  
Receptor Expression ◽  
B Cell Differentiation ◽  
Hematopoietic Stem ◽  
Inflammatory Protein ◽  
Macrophage Inflammatory Protein

The regulation of CCR6 (chemokine receptor 6) expression during B-cell ontogeny and antigen-driven B-cell differentiation was analyzed. None of the CD34+Lin− hematopoietic stem cell progenitors or the CD34+CD19+ (pro-B) or the CD19+CD10+ (pre-B/immature B cells) B-cell progenitors expressed CCR6. CCR6 is acquired when CD10 is lost and B-cell progeny matures, entering into the surface immunoglobulin D+ (sIgD+) mature B-cell pool. CCR6 is expressed by all bone marrow–, umbilical cord blood–, and peripheral blood–derived naive and/or memory B cells but is absent from germinal center (GC) B cells of secondary lymphoid organs. CCR6 is down-regulated after B-cell antigen receptor triggering and remains absent during differentiation into immunoglobulin-secreting plasma cells, whereas it is reacquired at the stage of post-GC memory B cells. Thus, within the B-cell compartment, CCR6 expression is restricted to functionally mature cells capable of responding to antigen challenge. In transmigration chemotactic assays, macrophage inflammatory protein (MIP)-3α/CC chemokine ligand 20 (CCL20) induced vigorous migration of B cells with differential chemotactic preference toward sIgD− memory B cells. These data suggest that restricted patterns of CCR6 expression and MIP-3α/CCL20 responsiveness are integral parts of the process of B-lineage maturation and antigen-driven B-cell differentiation.

scholarly journals THU0043 EXPRESSION OF B CELL CHEMOKINE-CHEMOKINE RECEPTOR PATHWAYS IS ALTERED IN GIANT CELL ARTERITIS

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 234.2-234
Author(s):  
J. Graver ◽  
A. Boots ◽  
W. Abdulahad ◽  
J. Bijzet ◽  
D. Wolbers ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Chemokine Receptor ◽  
Temporal Artery ◽  
Absolute Number ◽  
Memory B Cells ◽  
Receptor Expression ◽  
Healthy Controls ◽  
B Cell Differentiation

Background:The presence of organised B cells in both cranial-giant cell arteritis (C-GCA) (temporal artery) and large vessel (LV)-GCA (aorta) has previously been documented. The number and the extent of organisation of B cells in tertiary lymphoid organs (TLO) was more prominent in the aorta than in the temporal artery, suggesting possible differences in B cell phenotype, kinetics and tropism between C-GCA and LV-GCA.Objectives:We sought to analyse B cell differentiation subsets in both C-GCA and LV-GCA and to investigate differences in the expression of chemokine pathways involved in B cell migration and TLO organisation.Methods:Blood was collected from C-GCA (n=11) and LV-GCA (n=22) patients at baseline, before start of glucocorticoid treatment, and after 3 months of treatment. The LV-GCA groups consisted of 11 patients with isolated LV-GCA and 11 patients with overlap LV/C-GCA. Also, age- and sex- matched healthy controls (HC, n=24) were included. The following chemokines were measured with Luminex in the sera of patients and HC: BAFF, CCL19, CCL21, CXCL9, CXCL10, CXCL11, CXCL12, and CXCL13. Thawed PBMC of 7 C-GCA, 10 LV-GCA and 24 HC were stained with antibodies against CD19, CD27, IgD, IgM, CD38, CXCR3, CXCR4, CXCR5, and CCR7 to allow identification of B cell differentiation subsets and their chemokine receptor expression.Results:We found a lower absolute number of CXCR3+ memory and double negative (late stage) B cells in GCA patients when compared to healthy controls. Also, the absolute number of CXCR5+ memory B cells was lower in patients than in controls. Chemokine receptor expression on circulating B cells did not significantly differ between C-GCA and LV-GCA at baseline. After 3 months of treatment, frequencies and absolute numbers of both CXCR3+ and CXCR5+ memory B cells increased. In sera of all GCA patients, CXCL9 (which is a chemokine involved in migration of B cells to sites of inflammation) and CXCL13 (which is involved in local organization of B cells) were significantly increased. BAFF and CCL21 were increased only in LV-GCA when compared to HC. Serum chemokine levels did not differ between C-GCA and LV-GCA patients. An inverse correlation was observed between B cell counts and CXCL9 as well as CXCL13 in LV-GCA, only. After 3 months of treatment, CXCL9 levels remained elevated whereas CXCL13 increased even further.Conclusion:At diagnosis, CXCL9 and CXCL13 were significantly increased in all GCA patients as compared to HC. Elevated CXCL9 levels inversely correlated with B cells numbers in LV-GCA, only, which may suggest that B cells preferentially migrate to the inflamed aorta via a mechanism involving CXCL9. In addition, CXCL13 may be linked to local TLO organization in LV-GCA. Currently, we are studying the local expression of chemokines and chemokine receptors at the site of inflammation in both C- and LV-GCA.Disclosure of Interests:Jacoba Graver: None declared, Annemieke Boots Consultant of: Grünenthal Gmbh until 2017, Wayel Abdulahad: None declared, Johan Bijzet: None declared, Daphne Wolbers: None declared, Elisabeth Brouwer Consultant of: Roche (consultancy fee 2017 and 2018 paid to the UMCG), Speakers bureau: Roche (2017 and 2018 paid to the UMCG), Maria Sandovici: None declared

AB0144 STRATIFICATION OF PATIENTS WITH PRIMARY SJÖGREN’S SYNDROME BY MEASURING B-CELL HEALTH

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 1372-1373
Author(s):  
G. M. Verstappen ◽  
J. C. Tempany ◽  
H. Cheon ◽  
A. Farchione ◽  
S. Downie-Doyle ◽  
...  
Keyword(s):  
Cell Division ◽  
Cell Differentiation ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
B Cell Differentiation ◽  
Research Support ◽  
Differentiation Capacity ◽  
Cell Responses ◽  
Healthy Donors

Background:Primary Sjögren’s syndrome (pSS) is a heterogeneous immune disorder with broad clinical phenotypes that can arise from a large number of genetic, hormonal, and environmental causes. B-cell hyperactivity is considered to be a pathogenic hallmark of pSS. However, whether B-cell hyperactivity in pSS patients is a result of polygenic, B cell-intrinsic factors, extrinsic factors, or both, is unclear. Despite controversies about the efficacy of rituximab, new B-cell targeting therapies are under investigation with promising early results. However, for such therapies to be successful, the etiology of B-cell hyperactivity in pSS needs to be clarified at the individual patient level.Objectives:To measure naïve B-cell function in pSS patients and healthy donors using quantitative immunology.Methods:We have developed standardised, quantitative functional assays of B-cell responses that measure division, death, differentiation and isotype switching, to reveal the innate programming of B cells in response to T-independent and dependent stimuli. This novel pipeline to measure B-cell health was developed to reveal the sum total of polygenic defects and underlying B-cell dysfunction at an individual level. For the current study, 25 pSS patients, fulfilling 2016 ACR-EULAR criteria, and 15 age-and gender-matched healthy donors were recruited. Standardized quantitative assays were used to directly measure B cell division, death and differentiation in response to T cell-independent (anti-Ig + CpG) and T-cell dependent (CD40L + IL-21) stimuli. Naïve B cells (IgD+CD27-) were sorted from peripheral blood mononuclear cells and were labeled with Cell Trace Violet at day 0 to track cell division until day 6. B cell differentiation was measured at day 5.Results:Application of our standardized assays, and accompanying parametric models, allowed us to study B cell-intrinsic defects in pSS patients to a range of stimuli. Strikingly, we demonstrated a hyperresponse of naïve B cells to combined B cell receptor (BCR) and Toll-like receptor (TLR)-9 stimulation in pSS patients. This hyperresponse was revealed by an increased mean division number (MDN) at day 5 in pSS patients compared with healthy donors (p=0.021). A higher MDN in pSS patients was observed at the cohort level and was likely attributed to an increased division burst (division destiny) time. The MDN upon BCR/TLR-9 stimulation correlated with serum IgG levels (rs=0.52; p=0.011). No difference in MDN of naïve B cells after T cell-dependent stimulation was observed between pSS patients and healthy donors. B cell differentiation capacity (e.g., plasmablast formation and isotype switching) after T cell-dependent stimulation was also assessed. At the cohort level, no difference in differentiation capacity between groups was observed, although some pSS patients showed higher plasmablast frequencies than healthy donors.Conclusion:Here, we demonstrate defects in B-cell responses both at the cohort level, as well as individual signatures of defective responses. Personalized profiles of B cell health in pSS patients reveal a group of hyperresponsive patients, specifically to combined BCR/TLR stimulation. These patients may benefit most from B-cell targeted therapies. Future studies will address whether profiles of B cell health might serve additional roles, such as prediction of disease trajectories, and thus accelerate early intervention and access to precision therapies.Disclosure of Interests:Gwenny M. Verstappen: None declared, Jessica Catherine Tempany: None declared, HoChan Cheon: None declared, Anthony Farchione: None declared, Sarah Downie-Doyle: None declared, Maureen Rischmueller Consultant of: Abbvie, Bristol-Meyer-Squibb, Celgene, Glaxo Smith Kline, Hospira, Janssen Cilag, MSD, Novartis, Pfizer, Roche, Sanofi, UCB, Ken R. Duffy: None declared, Frans G.M. Kroese Grant/research support from: Unrestricted grant from Bristol-Myers Squibb, Consultant of: Consultant for Bristol-Myers Squibb, Speakers bureau: Speaker for Bristol-Myers Squibb, Roche and Janssen-Cilag, Hendrika Bootsma Grant/research support from: Unrestricted grants from Bristol-Myers Squibb and Roche, Consultant of: Consultant for Bristol-Myers Squibb, Roche, Novartis, Medimmune, Union Chimique Belge, Speakers bureau: Speaker for Bristol-Myers Squibb and Novartis., Philip D. Hodgkin Grant/research support from: Medimmune, Vanessa L. Bryant Grant/research support from: CSL

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