Genetic Loss of NFAT2 Induces Profound Acceleration of CLL in the TCL1 Mouse Model

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 862-862
Author(s):  
Melanie Märklin ◽  
Stefanie Bugl ◽  
Jonas S. Heitmann ◽  
Alexandra Poljak ◽  
Bettina S ◽  
...  
Keyword(s):  
Bone Marrow ◽  
B Cells ◽  
Mouse Model ◽  
Transgenic Mice ◽  
B Cell ◽  
Peripheral Blood ◽  
Flow Cytometric Analysis ◽  
Knock Out ◽  
Flow Cytometric

Abstract Abstract 862 NFAT is a family of highly phosphorylated proteins residing in the cytoplasm of resting cells. Upon dephosphorylation by calcineurin, NFAT proteins translocate to the nucleus where they orchestrate developmental and activation programs in diverse cell types. NFAT is inactivated and relocated to the cytoplasm by a network of several kinases. Although identified originally as a major transcriptional regulator in T cells, it is now clear that NFAT transcription factors also possess important roles in other cells of the hematopoietic system including dendritic cells, mast cells, megakaryocytes and B cells. Several recent studies have demonstrated that Calcineurin/NFAT signaling is involved in the pathogenesis of a wide array of hematological malignancies including diffuse large B cell lymphoma, CLL as well as Burkitt and Burkitt-like lymphomas. Here, we analyzed the role of NFAT2 in the pathogenesis of B-CLL. For this purpose, we generated mice with a conditional NFAT2 knock out allele (NFAT2fl/fl). In order to achieve NFAT2 deletion limited to the B cell lineage, we bred NFAT2fl/fl mice to CD19-Cre mice, in which the Cre recombinase is expressed under the control of the B cell-specific CD19 promoter. To investigate the role of NFAT2 in the pathogenesis of CLL we made use of the Eμ-TCL1 transgenic mouse model in which the TCL1 oncogene is expressed under the control of the Eμ enhancer. TCL1 transgenic mice develop a human-like CLL at the age of approximately 14 weeks to which the animals eventually succumb at an average age of 10 months. To analyze the role of NFAT2 in CLL, we generated mice (n=10) whose B cells exhibited a specific deletion of this transcription factor in addition to their transgenic expression of the TCL1 oncogene (TCL1 CD19-Cre NFAT2fl/fl). TCL1 transgenic mice without an NFAT2 deletion served as controls (n=10). Mice with NFAT2 knock out exhibited a significantly accelerated accumulation of CD5+CD19+ CLL cells as compared to control animals. Flow cytometric analysis at distinct time points showed a tremendous infiltration by CD5+ B cells in the peritoneal cavity, spleen, lymph nodes, liver and bone marrow which was significantly stronger in the NFAT2 ko cohort. Most of the CD5+ B cells in TCL1+NFAT2 ko mice showed high expression of ZAP70 and CD38, whereas TCL1 transgenic mice only demonstrated very few CD5+ B cells with concomitant expression of ZAP70 and CD38. At approximately 26 weeks of age, NFAT2 ko mice showed an approximately 40 fold increased lymphocyte count in the peripheral blood than their litter mate controls (1500/μL vs. 60000/μL). Splenomegaly and lymphatic adenopathy was also significantly increased in the NFAT ko population. Furthermore, NFAT2 ko mice showed a dramatically reduced median survival (200 vs. 325 days) and maximum survival (265 vs. 398 days) in comparison to regular TCL1 transgenic mice. To investigate the effects of an NFAT2 ko on proliferation and apoptosis of CD5+CD19+ CLL cells, we performed in vivo BrdU incorporation assays with subsequent flow cytometric analysis. Interestingly, we could show that CLL cells isolated from spleens, bone marrow and peripheral blood from mice with an NFAT ko at an age of approximately 7 months exhibited significantly higher rates of proliferation than control animals. In summary, our data provide strong evidence that NFAT2 is a critical regulator of CD38 and ZAP70 expression and substantially controls cell cycle progression in CLL cells implicating Ca2+/NFAT signaling as a potential target for the treatment of this disease. Disclosures: No relevant conflicts of interest to declare.

NFAT2 Is a Critical Regulator Of Anergy Induction In CLL

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 869-869
Author(s):  
Melanie Märklin ◽  
Jonas S. Heitmann ◽  
B. Sc. ◽  
David Worbs ◽  
B. Sc. ◽  
...  
Keyword(s):  
Gene Expression ◽  
B Cells ◽  
Transgenic Mice ◽  
B Cell ◽  
Gene Expression Analysis ◽  
Target Genes ◽  
Flow Cytometric Analysis ◽  
Knock Out ◽  
Flow Cytometric

Abstract NFAT is a family of highly phosphorylated proteins residing in the cytoplasm of resting cells. Upon dephosphorylation by calcineurin, NFAT proteins translocate to the nucleus where they orchestrate developmental and activation programs in diverse cell types. CLL is a clonal disorder of mature B cells characterized by the expression of CD19, CD23 and CD5. With respect to prognosis, it constitutes a heterogeneous disease with some patients exhibiting an indolent course for many years and others progressing rapidly and requiring early treatment. Expression of CD38 and ZAP70 define a subgroup of patients with enhanced responsiveness to stimulation of the B cell receptor (BCR) complex and more aggessive disease. In contrast, another subset of CLL patients with more indolent course is characterized by an anergic B cell phenotype refering to B cell unresponsiveness to IgM ligation and essential lack of phosphotyrosine induction and calcium flux. Here, we analyzed the role of NFAT2 in the pathogenesis of B-CLL and in anergy induction in CLL cells. For this purpose, we generated mice with a conditional NFAT2 knock out allele (NFAT2fl/fl). In order to achieve NFAT2 deletion limited to the B cell lineage, we bred NFAT2fl/fl mice to CD19-Cre mice. To investigate the role of NFAT2 in the pathogenesis of CLL we made use of the Eµ-TCL1 transgenic mouse model in which the TCL1 oncogene is expressed under the control of the Eµ enhancer. TCL1 transgenic mice develop a human-like CLL at the age of approximately 14 wks to which the animals eventually succumb at an average age of 10 months. To analyze the role of NFAT2 in CLL, we generated mice (n=10) whose B cells exhibited a specific deletion of this transcription factor in addition to their transgenic expression of the TCL1 oncogene (TCL1 CD19-Cre NFAT2fl/fl). TCL1 transgenic mice without an NFAT2 deletion served as controls (n=10). To identify novel NFAT2 target genes in CLL cells, we performed a comparative gene expression analysis on CLL cells with intact NFAT2 expression and on CLL cells with NFAT2 deletion using affymetrix microarrays. Mice with NFAT2 knock out exhibited a significantly more aggressive disease course with accelerated accumulation of CD5+CD19+ CLL cells and a significantly reduced life expectancy (200 vs. 325 days) as compared to control animals. Flow cytometric analysis at distinct time points showed a pronounced infiltration by CD5+ B cells of the peritoneal cavity, spleen, lymph nodes, liver and bone marrow which was significantly stronger in the NFAT2 ko cohort. Most of the CD5+ B cells in TCL1+NFAT2 ko mice showed high expression of ZAP70 and CD38, whereas TCL1 transgenic mice only demonstrated very few CD5+ B cells with concomitant expression of ZAP70 and CD38. To investigate the effects of an NFAT2 ko on proliferation and apoptosis of CD5+CD19+ CLL cells, we performed in vivo BrdU incorporation assays with subsequent flow cytometric analysis. Interestingly, we could show that CLL cells isolated from spleens, bone marrow and peripheral blood from mice with an NFAT ko exhibited significantly higher rates of proliferation than control animals. To identify NFAT2 target genes resonsible for the observed alterations in the disease phenotype, we subsequently peformed a gene expression analysis with CD5+CD19+ CLL cells from TCL1+NFAT2 ko mice with CLL cells from TCL1+ mice serving as controls. Here, we detected a significantly altered expression of 22 genes associated with B cell anergy in the TCL1+NFAT2 ko cohort. The vast majority of these genes was expressed significantly less in the absence of NFAT2 with Lck, Pacsin1, Hspa14 and CD166 constituting the strongest hits with up to 10fold reduced gene expression. Downregulation of the identified target genes was subsequently confirmed using RT-PCR and Western Blotting. In summary, our data provide strong evidence that NFAT2 is a critical regulator of CD38 and ZAP70 expression and substantially controls cell cycle progression in CLL cells. In addition, we could show that NFAT2 controls the expression of several anergy-associated genes and that its absence prevents the acquisition of an anergic phenotype by the CLL cells correlating with a significantly more aggressive course of the disease. Taken together, our data demonstrate that NFAT2 plays an essential role in the pathogenesis of CLL and implicate this transcription factor as a potential target in its treatment. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Selection of antigen-specific, idiotype-positive B cells in transgenic mice expressing a rearranged M167-mu heavy chain gene.

1991 ◽  
Vol 174 (5) ◽  
pp. 1189-1201 ◽  
Author(s):  
J J Kenny ◽  
C O'Connell ◽  
D G Sieckmann ◽  
R T Fischer ◽  
D L Longo
Keyword(s):  
Bone Marrow ◽  
B Cells ◽  
Transgenic Mice ◽  
B Cell ◽  
Flow Cytometric Analysis ◽  
Low Frequency ◽  
Surface Expression ◽  
Chain Gene ◽  
Large Numbers ◽  
Selection Of

Flow cytometric analysis of antigen-specific, idiotype-positive (id+), B cell development in transgenic mice expressing a rearranged M167-mu gene shows that large numbers of phosphocholine (PC)-specific, M167-id+ B cells develop in the spleen and bone marrow of these mice. Random rearrangement of endogenous V kappa genes, in the absence of a subsequent receptor-driven selection, should give rise to equal numbers of T15- and M167-id+ B cells. The observed 100-500-fold amplification of M167-id+ B cells expressing an endogenous encoded V kappa 24]kappa 5 light chain in association with the M167 VH1-id transgene product appears to be an antigen driven, receptor-mediated process, since no amplification of non-PC-binding M167 VH1/V kappa 22, T15-id+ B cells occurs in these mu-only transgenic mice. The selection and amplification of antigen-specific, M167-id+ B cells requires surface expression of the mu transgene product; thus, no enhancement of M167-id+ B cells occurs in the M167 mu delta mem-transgenic mice, which cannot insert the mu transgene product into the B cell membrane. Surprisingly, no selection of PC-specific B cells occurs in M167-kappa-transgenic mice although large numbers of B cells expressing a crossreactive M167-id are present in the spleen and bone marrow of these mice. The failure to develop detectable numbers of M167-id+, PC-specific B cells in M167-kappa-transgenic mice may be due to a very low frequency of M167-VH-region formation during endogenous rearrangement of VH1 to D-JH segments. The somatic generation of the M167 version of a rearranged VH1 gene may occur in less than one of every 10(5) bone marrow B cells, and a 500-fold amplification of this M167-Id+ B cell would not be detectable by flow cytometry even though the anti-PC antibody produced by these B cells is detectable in the serum of M167-kappa-transgenic mice after immunization with PC.

scholarly journals SOX11 Cooperates with CCND1 in Mantle Cell Lymphoma Pathogenesis

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1253-1253 ◽  
Author(s):  
Pei-Yu Kuo ◽  
Zewei Jiang ◽  
Deepak Perumal ◽  
Violetta V Leshchenko ◽  
Alessandro Lagana' ◽  
...  
Keyword(s):  
Bone Marrow ◽  
B Cells ◽  
Mouse Model ◽  
Transgenic Mice ◽  
B Cell ◽  
Transgenic Mouse ◽  
Cell Lymphoma ◽  
Mantle Cell ◽  
Sox11 Expression

Abstract MCL (Mantle cell lymphoma) is an aggressive and incurable B cell malignancy with a median survival of 5-6 years. Cyclin D1 (CCND1) overexpression is a key diagnostic feature of this disease, observed in more than 90% of MCL tumors. However, murine models over-expressing CCND1 in B cells do not recapitulate the phenotype of MCL. The SOX11 transcription factor is aberrantly expressed in 80-90% of primary MCL. Our published data demonstrated that SOX11 binds and functionally regulates key components in multiple oncogenic pathways in MCL such as WNT and TGFβ pathways. Recent studies have also showed that SOX11 regulates PAX5 and PDGFA to block differentiation and facilitate lymphoma growth. We thus hypothesize that SOX11 expression may contribute directly and functionally cooperate with CCND1 in MCL pathogenesis. To study the role of SOX11 in MCL tumorigenesis in vivo, we have generated a novel SOX11 transgenic mouse model with B cell-specific tissue expression under the E-mu enhancer and an IRES-eGFP tag to monitor the expression of SOX11. The presence of SOX11 can be readily detected in pre-pro-B stage in the bone marrow coincided with the activation of E-mu enhancer and was persistent through all stages of B cells. SOX11 over-expression in our mouse model led to an aberrant oligo-clonal expansion of CD19+/CD5+ B cells. This phenotype was evident in all SOX11 transgenic mice studied (100% penetrance, n= 42 mice) with an average of 7-12 fold increase (p<0.03) of the CD5+ B cell populations as compared to littermate controls starting from 1.5 months. Using Mass Cytometry (CyTOF), we further characterized this B cell population to be CD23-, CD21/35 dim, CD138-, high surface IgM, and variable IgD expression, a naive B cell phenotype consistent with an early precursor stage of human MCL. This MCL phenotype is most prominent in peripheral blood and spleen and, to a much lesser extent, in peritoneal cavity and bone marrow. Transplanting bone marrow from SOX11 transgenic mouse to lethally-irradiated wild type mice successfully transferred the observed phenotypic CD19+/CD5+/CD23- B cell hyperplasia, suggesting that SOX11 overexpression in early B cells drives this MCL phenotype. We next studied the cooperation between CCND1 and SOX11 by crossing SOX11 transgenic mice with a CCND1 transgenic mouse model, which over-expresses CCND1 in a B-cell specific manner under a similar E-mu enhancer. Overexpression of both CCND1 and SOX11 in the double transgenic mice model dramatically enhanced (average 10x, range 6x-30x) the aberrant MCL phenotype (CD19+/CD5+/CD23-) in peripheral blood, spleen, bone marrow, peritoneal cavity and lymph nodes compared to age-matched SOX11 and CCND1 single-transgenic mice. We report here the first direct evidence in vivo that SOX11 expression drives an aberrant expansion of B cells consistent with early human MCL and functionally collaborates with CCND1 in "full blown" MCL pathogenesis, mimicking the commonly observed co-expression of SOX11 and CCND1 in most human MCL tumors. This model captures the underpinning molecular pathogenesis events occurred in the majority of human MCL and overcomes constraints of previous MCL models that develop a phenotype after long latency or with low penetrance, making it a valuable tool for testing anti-MCL therapeutics. We are currently developing small molecule SOX11 inhibitors using SOX11 DNA binding domain models and consensus SOX11 binding nucleotides to screen a large library of compounds to identify new therapeutics for this fatal disease and gain better understanding of the molecular mechanisms of MCL tumorigenesis. Disclosures No relevant conflicts of interest to declare.

Role of the Hypoxic Bone Marrow Microenvironment in Multiple Myeloma Tumor Progression.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2348-2348
Author(s):  
Kewal Asosingh ◽  
Hendrik De Raeve ◽  
Mark de Ridder ◽  
Guy A. Storme ◽  
Angelo Willems ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Mouse Model ◽  
Tumor Progression ◽  
Flow Cytometric Analysis ◽  
Surrogate Marker ◽  
Hypoxic Conditions ◽  
Flow Cytometric

Abstract Recently we reported that pre-clinical myeloma disease progression in the 5T2MM mouse model is characterized by predominant CD45+ MM-cells in the early, pre-angiogenic stage stage of slow tumor progression, followed by expansion of CD45− MM-cells during the subsequent angiogenic stage of progressive tumor growth. Unlike other cancer cells, multiple myeloma (MM) cells have to survive and to grow in a microenvironment which is already hypoxic by nature. This hypoxic bone marrow (BM) microenvironment is essential for normal hematopoiesis. However, the role of BM hypoxia in myeloma tumor progression is not known. Herein we addressed this topic in the 5T2MM mouse model. Flow cytometric analysis of control mice and 5T2MM diseased mice injected with pimonidazole hypoxyprobe indicated that both normal BM and myeloma infiltrated BM are hypoxic. However, in myelomatous BM the hypoxia was significantly decreased. Analysis of HIF-1a expression, a surrogate marker of hypoxia, by flow cytometry also demonstrated significantly lower levels of hypoxia in myeloma infiltrated BM. HIF-1a expression was found in 5T2MM-cells and was significantly higher compared to the non-tumor cell fraction. In vitro culturing of 5T2MM cells under hypoxic conditions, indicated increased activation of apoptosis inducing caspase-3 in the CD45− MM-fraction, but not in the CD45+ 5T2MM-cells, suggesting that native BM hypoxia selects the tumor population for tumor initiating CD45+ 5T2MM-cells. Although angiogeneic switch and angiogeneic heterogeneity has been reported in MM, the role of myeloma associated angiogensis is remains unclear. The decreased hypoxia in myeloma infiltrated BM adds strength to the hypothesis that myeloma associated neovascularization is functional by increasing BM oxygenation. The data also suggest that the angiogenesis allows expansion of CD45− 5T2MM-cells by decreasing BM hypoxia. All together, these findings suggest an important role of BM hypoxia in myeloma tumor progression.

scholarly journals Regulation of Hematopoiesis By the Coagulation Receptor Thrombomodulin

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 4750-4750 ◽  
Author(s):  
Sreemanti Basu ◽  
Irene Hernandez ◽  
Mark Zogg ◽  
Karen-Sue B. Carlson ◽  
Hartmut Weiler
Keyword(s):  
Bone Marrow ◽  
B Cells ◽  
B Cell ◽  
Peripheral Blood ◽  
Protein C ◽  
Nature Medicine ◽  
Absolute Number ◽  
Flow Cytometric ◽  
The Absolute ◽  
B Cell Precursors

Abstract BACKGROUND: Pharmacologic supplementation of protein C pathway function by infusion of recombinant Thbd or activated protein C supports recovery of hematopoietic function from lethal radiation injury in mice [Geiger et al., Nature Medicine, 2012]. Partial Thbd deficiency in hematopoietic stem and progenitor cells (HSPC) or bone marrow endothelium results in augmented sensitivity towards radiation injury [Geiger et al., Nature Medicine, 2012]. The underlying cellular and molecular mechanisms of Thbd function in hematopoiesis are not yet characterized. The objective of the current study was to determine the expression pattern and functional role of Thbd in HSPC. RESULTS: Flow cytometric analysis was employed to detect Thbd expression in defined subsets of murine HSPC. Thbd was co-expressed with the endothelial protein C receptor (Procr/EPCR) in the majority of bona fide stem cells with long-term-repopulating capacity (LT-HSC), and was also expressed on EPCR-negative stem cells with short-term repopulating capacity (ST-HSC), multipotent progenitors (MPP), common lymphoid progenitors (CLP), common myeloid progenitors (CMP), and granulocyte-monocyte progenitors (GMP). In contrast, only a subset of megakaryocyte-erythrocyte progenitors (MEP) expressed low levels of Thbd. In the bone marrow, Thbd was also expressed by B cells in early stages of maturation (from progenitor B cell stage till immature stage). In this lineage, the fraction of Thbd-positive cells was inversely correlated with the stage of B cell maturation. In addition, Thbd was detected in three distinct subsets of bone marrow-resident myeloid cells (CD11b+CD115+, CD11b+CD11c+ and CD11b-CD115+). Thbd expression outside the bone marrow was limited to a small fraction of hematopoietic cells (2-5% in the peripheral blood and spleen). These cells included myeloid cells (macrophage/monocyte and dendritic cells). Approximately 1-2% of all B cells in the peripheral blood and the spleen expressed Thbd, possibly reflecting recent bone marrow emigrants. Thbd expression was largely absent from splenic follicular and marginal zone B cells. Adult mice with complete, ubiquitous ablation of Thbd gene function (Meox2Cre-ThbdloxP -mice; "Thbd-null") were generated to analyze the functional role of Thbd in hematopoiesis. Thbd-null mice exhibited low birth weight, but only a mild prothrombotic diathesis, reflected in occasional peripheral vascular occlusion limited to the tail vein. Flow cytometric analyses revealed increased frequency of LT- and ST-HSC, a trend towards reduced CLP frequency, but normal relative abundance of MPP, CMP, GMP, and MEP. Thbd deficiency was also associated with a significant increase in the absolute number of LT-HSC and a reduction in the absolute number of CLP in the bone marrow. No such derangements were observed in mice lacking EPCR. In functional assays, bone marrow from wildtype and mutant mice yielded comparable numbers of CFU-GM. In contrast, the number of CFU-GM was increased in the spleen and peripheral blood of Thbd-null animals. The absolute number and frequency of all B cell precursors, as well as mature B cells in the bone marrow was reduced by ~50%. In the spleen, the absolute number of B cells was increased, whereas other hematopoietic populations in peripheral organs of Thbd-null mice were identical to that of wildtype controls. CONCLUSION: Thbd is expressed in the majority of hematopoietic progenitor cells in the bone marrow, including LT- and ST-HSC, and B cell precursors. Despite abundant Thbd expression in bone marrow resident cells and a modest prothrombotic phenotype, complete Thbd deficiency had only mild effects on steady-state hematopoiesis. Hematopoietic derangements were limited to the B cell compartment, and an Increased presence of CFU-GM in the spleen and peripheral blood of Thbd-null mice, possibly reflecting stimaulation of extramedullary hematopoiesis and/or altered bone marrow retention of precursors. Disclosures No relevant conflicts of interest to declare.

A NUP98-HOXD13 Fusion Gene Impairs B Lymphocyte Development and Function In a Mouse Model for Myelodysplastic Syndrome

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 279-279
Author(s):  
Abdul Gafoor A. Puthiyaveetil ◽  
Bettina Heid ◽  
David L. Caudell
Keyword(s):  
B Cells ◽  
Transgenic Mice ◽  
B Cell ◽  
B Lymphocytes ◽  
Marginal Zone ◽  
Fusion Gene ◽  
Flow Cytometric Analysis ◽  
Flow Cytometric ◽  
Cell Fractions ◽  
And Function

Abstract Abstract 279 Transgenic mice which express the fusion gene NUP98-HOXD13 (NHD13) have been shown to develop characteristic features of Myelodysplastic syndrome (MDS) including impaired hematopoietic differentiation and peripheral blood cytopenias in the presence of normocellular or hypercellular bone marrow (BM). It is evident that B-cells play a role in the progression of MDS by immune modulation or as direct targets of mutations resulting in ALL, or as cells that influence the BM microenvironment in which a neoplastic myeloid clone evolves. Choi and colleagues suggested a block in differentiation during the early development of B lymphocytes in the BM of NHD13 mice leading to lymphopenia consistent with the observation in some MDS patients. In this study, we sought to further delineate the role of NHD13 on B lymphocytes which escaped the initial differentiation block in the BM. We hypothesized that NHD13 impairs maturation and function of IgM+ B lymphocytes contributing to immunodeficiency. To study this, we performed blood smear examination, Complete Blood Counts (CBC), quantitative ELISA for antibody concentrations, and flow cytometric analysis of B cell fractions from the BM and spleen in 8–12 week-old transgenic and wild type (WT) mice. CBCs revealed significant lymphopenia and ELISA showed higher IgM concentrations (n=10, p<0.001), reduced levels of IgG1 (n=10, p<0.05) and IgE (n=10, p<0.01). The IgG2a, IgG2b, and IgG3 antibody levels were comparable to WT counterparts. Flow cytometric analysis of BM and splenic B cell fractions revealed reduced numbers of B cells in Hardy fractions D and F (n=10, p<0.01) indicative of impaired differentiation prior to these stages; splenic fractions in NHD13 mice were comparable to WT controls. Next, to assess the peripheral maturation and functional efficiency of B lymphocytes in the context of a comprehensive immune stimulation, a cohort of five WT and five preclinical transgenic mice were injected with 100 μ g dinitrophenol (DNP) followed by a booster dose on day 21. Mice were euthanized on day 28 and whole blood, spleen, lymphnodes and BM were harvested. CBC evaluation revealed significant lymphopenia in NHD13 mice (n=5, p<0.001). Quantitative ELISA for DNP specific antibodies showed comparable levels of serum IgM and significantly reduced levels of serum IgG1 (n=5, p<0.001), IgG2a (n=5, p<0.001), IgG2b (n=5, p<0.01), IgG3 (n=5, p<0.001) and IgE (n=5, p<0.01). Flow cytometric analysis of peripheral blood showed reduced numbers of B220+ IgM+ B cells (n=5, p<0.01), but comparable percentages of CD4+ and CD8+ T-cells. Detailed flow cytometric analysis of B-cell fractions in the BM and spleen of DNP-stimulated mice revealed a reduction in subpopulations of B lymphocytes. The earliest B cell lineage population, Pre-Pro B, was comparable to the WT controls. Hardy Pro B fraction B (n=5, p<0.001) and Pre B fractions E (n=5, p<0.01) and F (n=5, p<0.01) from BM of stimulated mice were significantly reduced in contrast to fractions C and C', which were higher (n=5, p<0.05 and p<0.001 respectively), indicative of cell growth arrest at these stages. Flow cytometry of splenic B-cell fractions from the DNP-stimulated mice showed significantly lower Transitional 1 (n=5, p<0.01), Follicular (n=5, p<0.05) and Marginal Zone (n=5, p<0.001) populations upon antigenic stimulation suggestive of defective clonal expansion of IgM+ cells even after escaping the block in the BM. Histopathology of the spleen revealed smaller lymphoid follicles with poorly developed mantle and marginal zone regions in the transgenic mice when compared to WT controls, consistent with the flow cytometric data. This study indicates that when NHD13 mice are immunologically challenged, B lymphocytes undergo impaired differentiation in the BM and maturation in the spleen, as well as reduced antibody class switching and subsequently lower antibody production. Analysis of B cell subsets during development and specific IgG/IgE antibody production, suggest that the NHD13 transgene might impair VDJ gene recombination and class switch recombination that are critical during these phases of B cell development. Disclosures: No relevant conflicts of interest to declare.

Ca2+/NFAT Signaling Regulates the Expression CD38 and ZAP70 in Murine B Cells and Controls B1a Cell Homeostasis

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 183-183
Author(s):  
Melanie Märklin ◽  
Stefanie Bugl ◽  
Marina Bechtel ◽  
Alexandra Poljak ◽  
Hans-Georg Kopp ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Flow Cytometry ◽  
B Cells ◽  
B Cell ◽  
Precursor Cell ◽  
Lymphocytic Leukemia ◽  
Knock Out ◽  
B1a Cells ◽  
Knock Out Mice

Abstract Abstract 183 NFAT is a family of highly phosphorylated proteins residing in the cytoplasm of resting cells. Upon dephosphorylation by calcineurin, NFAT proteins translocate to the nucleus where they orchestrate developmental and activation programs in diverse cell types. NFAT is inactivated and relocated to the cutoplasm by a network of several kinases including CK-1, GSK-3 and DYRK. Although identified originally as a major transcriptional regulator in T cells, it is now clear that NFAT transcription factors also possess important roles in other cells of the hematopoietic system including dendritic cells, mast cells, megakaryocytes and B cells. Here we have analyzed the role of NFAT2 in B cell development. Analysis of the role of this family member in hematopoiesis has been complicated by the fact that deletion of this gene is embryonic lethal around ED 13 because of defects in heart valve development. To circumvent this problem we generated mice with a conditional NFAT2 knock out allele (NFAT2fl/fl). In order to achieve NFAT2 deletion limited to the B cell lineage, we bred NFAT2fl/fl mice to CD19-Cre mice, in which the Cre recombinase is expressed under the control of the B cell-specific cd19 promoter. B cells from these mice were isolated using CD19-labeled magnetic beads and subjected to analysis by flow cytometry. While CD19+ splenocytes from conditional NFAT2 knock-out mice occurred in normal numbers, these cells showed significantly reduced expression of CD38 and ZAP70 upon stimulation with anti-IgM antibody as compared to CD19+ splenocytes from wild-type controls. The reduction of these proteins could also be detected in B cells isolated from the peripheral blood and from bone marrow and was confirmed by western blotting and quantitative RT-PCR. CD38 and ZAP70 are well characterized prognostic factors in chronic lymphocytic leukemia (CLL) and their increased expression has been shown to correlate with poor patient survival. Our data indicate that the expression of these markers is at least in part regulated by Ca2+/NFAT signaling and that deregulation of this pathway can contribute to their overexpression in disease. Next we analyzed bone marrow and peritoneal lavages from conditional NFAT knock-out mice by flow cytometry. While we found no significant differences in the abundance of B cell subpopulations in bone marrow, we detected an almost complete absence of CD5+CD43+ B1a cells in the peritoneal cavity, clearly demonstrating the requirement of NFAT2 in the development of this subclass. B1a cells are a phenotypically and functionally distinct population of B cells which are long-lived and typically express CD5, CD43 and high levels of surface IgM together with low surface IgD and CD45 (B220). A human B cell equivalent of the murine B1a cell has been suggested as the leukemic precursor cell in chronic lymphocytic leukemia (CLL). To further delineate the role of NFAT2 in the development of B1a cells we determined the abundance of B1 progenitor cells (B1P) in bone marrow and spleen by FACS analysis. In NFAT2 knock-out mice we observed a significant reduction of the frequency of B220- CD19+ CD93+ B1P cells in bone marrow (0.8% vs. 4.7%) and spleen (0.16% vs. 0.82%) demonstrating that NFAT2 is essential for normal development of this precursor cell population. In summary, our data provide strong evidence that NFAT2 is critical for the expression of CD38 and ZAP70 in B cells and substantially controls B1a cell homeostasis implicating Ca2+/NFAT signaling as a potential target for the treatment of CLL. Disclosures: No relevant conflicts of interest to declare.

scholarly journals POS0387 ACPA STATUS CORRELATES WITH DIFFERENTIAL IMMUNE PROFILE OF RHEUMATOID ARTHRITIS PATIENTS

2021 ◽  
Vol 80 (Suppl 1) ◽  
pp. 423.2-424
Author(s):  
A. Floudas ◽  
M. Canavan ◽  
T. McGarry ◽  
V. Krishna ◽  
S. Nagpal ◽  
...  
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Synovial Tissue ◽  
Peripheral Blood ◽  
Flow Cytometric Analysis ◽  
Algorithm Analysis ◽  
Treat To Target ◽  
Tnf Α ◽  
Acpa Status

Background:Rheumatoid arthritis (RA) is a progressive erosive autoimmune disease that affects 1% of the world population. Anti-citrullinated protein autoantibodies (ACPA) are routinely used for the diagnosis of RA, however 20-30% of patients are ACPA negative. ACPA status is a delineator of RA disease endotypes with similar clinical manifestation but potentially different pathophysiology. Elucidating the underlying mechanisms of disease pathogenesis could inform a treat to target approach for both ACPA-positive and ACPA-negative RA patients.Objectives:To identify peripheral blood and synovial tissue immune population differences that associate with RA disease endotype.To identify unique RA patient synovial tissue gene signatures and enriched pathways that correlate with ACPA status.Methods:Detailed high dimensionality flow cytometric analysis with supervised and unsupervised algorithm analysis of ACPApos and ACPAneg RA patient peripheral blood and synovial tissue single cell suspensions. Ex vivo peripheral blood and synovial tissue T cell stimulation and cytokine production characterisation. RNAseq analysis with specific pathway enrichment analysis of APCApos and ACPAneg RA patient synovial tissue biopsies.Results:Detailed profiling based on high dimensionality flow cytometric analysis of key peripheral blood and synovial tissue immune populations including B cells, T follicular helper (Tfh) cells, T peripheral helper cells (Tph) and CD4 T cell proinflammatory cytokine responses with supervised and unsupervised algorithm analysis revealed unique RA patient peripheral blood B cell and Tfh cell profiles. ACPApos RA patients were characterised by significantly (*P=0.03) increased frequency of Tfh (CXCR5+CD4+) cells and distinct clustering influenced by increased switched (IgD-CD27+) and DN (IgD-CD27-) memory B cells compared to APCAneg RA patients. Surprisingly synovial tissue B cell subpopulation distribution was similar between ACPAneg and ACPApos RA patients, with significant accumulation of switched and double negative memory B cells, highlighting a key role for specific B cell subsets in both disease endotypes. Interestingly, synovial tissue CD4 T cell proinflammatory cytokine (TNF-α, IFN-γ, IL-2, GM-CSF, IL-17A, IL-22, IL-4) production was markedly different between ACPAneg and APCApos RA patients with hierarchical clustering and PCA analysis revealing endotype specific cytokine profiles with ACPAneg RA patient synovial T cells showing increased TNF-α (P=0.01) expression. RNAseq analysis of RA patient synovial tissue revealed significant disease endotype specific gene signatures with specific enrichment for B cell receptor signalling and T cell specific pathways in ACPApos compared to ACPAneg RA patients. Additionally, significantly different chemokine receptor expression based on RA patient ACPA status was observed with increased CXCR3 (P<0.001), CCR7 (P=0.002), and CCR2 (P=0.004) but decreased CXCR7 (P=0.007) expression in APCApos compared to ACPAneg RA patient synovial biopsies.Conclusion:ACPA status associates with unique synovial tissue immune cell and gene profile signatures highlighting differences in the underlying immunological mechanisms involved, therefore reinforcing the need for a treat to target approach for both endotypes of RA.Figure 1.RNAseq analysis of synovial tissue biopsies revealed specific T cell related pathway enrichment in ACPA positive compared to ACPA negative RA patients (n=50, analysis performed with the DESq2 and pathfindeR pipelines in R).Disclosure of Interests:Achilleas Floudas: None declared, Mary Canavan: None declared, Trudy McGarry Employee of: Novartis, Vinod Krishna Employee of: Janssen, Sunil Nagpal Employee of: Janssen, GSK, Douglas Veale Speakers bureau: Abbvie, Janssen, Novartis, MSD, Pfizer, UCB, Consultant of: Abbvie, Janssen, Novartis, MSD, Pfizer, UCB, Grant/research support from: Janssen, Abbvie, Pfizer, UCB, Ursula Fearon Speakers bureau: Abbvie, Grant/research support from: Janssen, Abbvie, Pfizer, UCB

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