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  • The American Association of Immunologists  (27)
  • 1
    Online Resource
    Online Resource
    The American Association of Immunologists ; 2003
    In:  The Journal of Immunology Vol. 171, No. 12 ( 2003-12-15), p. 6381-6388
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 171, No. 12 ( 2003-12-15), p. 6381-6388
    Abstract: Positive selection is required for B cell differentiation, as indicated by the requirement for expression of the pre-B cell receptor (pre-BCR) and the BCR at the pre-B and immature B cell stages, respectively. Positive selection mediated by a tonic signal from these receptors is sufficient to drive B cell differentiation beyond the pre-B and immature B cell stages, but it is unclear whether additional positive selection signals are required for differentiation to a mature B-2 cell. We have identified a population of Ig transgenic B cells that differentiatively arrest at a transitional B cell stage in the spleen. They exhibit no evidence of Ag encounter or negative selection and can differentiate to mature B-2 cells in vivo upon weak BCR stimulation or adoptive transfer to irradiated hosts. These data are consistent with a requirement for a ligand-mediated BCR signal for differentiation to a mature B-2 cell.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
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    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2003
    detail.hit.zdb_id: 1475085-5
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  • 2
    Online Resource
    Online Resource
    The American Association of Immunologists ; 2012
    In:  The Journal of Immunology Vol. 188, No. 1_Supplement ( 2012-05-01), p. 176.9-176.9
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 188, No. 1_Supplement ( 2012-05-01), p. 176.9-176.9
    Abstract: FCMR is a Fc receptor specific for pentameric IgM expressed at high levels by B cells. Although circulating IgM has profound effects on responses to pathogens, autoimmunity and B cell homeostasis, the biologic consequences of its binding to FCMR are poorly understood. We interrogated FCMR contributions to B cell function by studying mice lacking FCMR. FCMR transcripts are expressed at highest levels by follicular (FO) B cells and at much lower levels by developing B cells and other mature B cell subsets. FCMR-deficient mice have reduced numbers of developing B cells, splenic FO and peritoneal B-2 cells, but increased levels of peritoneal B-1a cells and autoantibodies. Following immunization, germinal center B cell and plasma cell numbers are increased. FCMR-deficient B cells are resistant to apoptosis induced by BCR ligation. Our studies demonstrate that FCMR functions are critical for B cell homeostasis, the prevention of autoreactive B cells and responsiveness to antigenic challenge.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    RVK:
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    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2012
    detail.hit.zdb_id: 1475085-5
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  • 3
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 195, No. 4 ( 2015-08-15), p. 1480-1488
    Abstract: IFN regulatory factor 8 (IRF8) is constitutively expressed in monocytes and B cells and plays a critical role in the functional maturation of microglia cells. It is induced in T cells following Ag stimulation, but its functions are less well understood. However, recent studies in mice with T cell–specific Irf8 disruption under direction of the Lck promoter (LCK-IRF8KO) suggest that IRF8 directs a silencing program for Th17 differentiation, and IL-17 production is markedly increased in IRF8-deficient T cells. Paradoxically, loss of IRF8 in T cells has no effect on the development or severity of experimental autoimmune encephalomyelitis (EAE), although exacerbating colitis in a mouse colitis model. In contrast, mice with a macrophage/microglia-specific Irf8 disruption are resistant to EAE, further confounding our understanding of the roles of IRF8 in host immunity and autoimmunity. To clarify the role of IRF8 in autoimmune diseases, we have generated two mouse strains with targeted deletion of Irf8 in retinal cells, including microglial cells and a third mouse strain with targeted Irf8 deletion in T cells under direction of the nonpromiscuous, CD4 promoter (CD4-IRF8KO). In contrast to the report that IRF8 deletion in T cells has no effect on EAE, experimental autoimmune uveitis is exacerbated in CD4-IRF8KO mice and disease enhancement correlates with significant expansion of Th17 cells and a reduction in T regulatory cells. In contrast to CD4-IRF8KO mice, Irf8 deletion in retinal cells confers protection from uveitis, underscoring divergent and tissue-specific roles of IRF8 in host immunity. These results raise a cautionary note in the context of therapeutic targeting of IRF8.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
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    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2015
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  • 4
    Online Resource
    Online Resource
    The American Association of Immunologists ; 2012
    In:  The Journal of Immunology Vol. 188, No. 1_Supplement ( 2012-05-01), p. 67.2-67.2
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 188, No. 1_Supplement ( 2012-05-01), p. 67.2-67.2
    Abstract: B-1a cells are found to contribute significantly to circulating natural antibodies and mucosal immunity as well as to immunoregulation. These various functional attributes of B-1a are often presented as reflecting the repertoire of all B-1a cells, while understanding how these functions are fulfilled at the clonal level is rather limited. Here we show that B-1a cells can be subdivided into two distinct stable subsets based on differing expression of the plasma cell alloantigen 1 (PC1), also known as ectonucleotide pyrophosphatase phosphodiesterase 1 (ENPP1), an enzyme involved primarily in hydrolysis of ATP at the cell surface. One subset that we term PC1lo, expresses ENPP1 at low levels, whereas the second subset, designated PC1hi, expresses ENPP1 at high levels. These subsets are distinguishable by gene expression profiles, VH gene usage and time of development. Adoptively transferred PC1lo cells secret significantly more circulating natural IgM and intestinal IgA than PC1hi cells. In contrast, PC1hi cells produce more IL-10 than PC-1lo cells when stimulated with LPS and PMA. Furthermore, PC1lo cells generate antigen-specific IgM responses to pneumococcal polysaccharide antigens whereas PC1hi cells do not. We conclude that the classic B-1a functions segregate quite cleanly between these two subsets and the identification of PC1lo and PC1hi cells extends the concept of a layered immune system.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
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    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2012
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  • 5
    Online Resource
    Online Resource
    The American Association of Immunologists ; 2019
    In:  The Journal of Immunology Vol. 202, No. 1_Supplement ( 2019-05-01), p. 179.1-179.1
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 202, No. 1_Supplement ( 2019-05-01), p. 179.1-179.1
    Abstract: Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the presence of autoantibodies in serum and multi-organ inflammation. Immune complex deposition in kidney can lead to lupus nephritis, which is a major risk factor for morbidity and mortality in SLE. Using FcγRIIB−/− mice as a lupus animal model, we performed a detailed time course analysis of the extent of the spontaneous leukocyte activation and expansion in spleen and in renal, inguinal, mesenteric lymph nodes. We then correlated the data with the onset of pathology and leukocyte infiltration in the kidney. In the FcγRIIB−/− mouse model, effector-memory CD4 cells and germinal centers appeared first in the spleen and renal lymph nodes, but not in other immune organs such as inguinal or mesenteric lymph nodes. As the disease progresses in these mice, lymphocytes undergo an extensive expansion that involves all immune organs in a systemic manner. At the same moment we can detect the first signs of kidney pathology, measured by histopathology and by the levels of creatinine and albumin in urine. In FcγRIIB−/− mice, the onset of kidney pathology correlates with leukocyte infiltration in kidney, detected both by parenchyma-restricted flow cytometry and histopathology. Macrophages, CD4 and CD8 cells are found both in glomerular and interstitial spaces with the exclusion of B cells, most likely suggesting a role for T cells and/or macrophage specific chemokine signals in lupus nephritic kidney.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
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    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2019
    detail.hit.zdb_id: 1475085-5
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  • 6
    Online Resource
    Online Resource
    The American Association of Immunologists ; 2013
    In:  The Journal of Immunology Vol. 190, No. 3 ( 2013-02-01), p. 987-996
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 190, No. 3 ( 2013-02-01), p. 987-996
    Abstract: FcR specific for pentameric IgM (FCMR) is expressed at high levels by B cells. Although circulating IgM has profound effects on responses to pathogens, autoimmunity, and B cell homeostasis, the biologic consequences of its binding to FCMR are poorly understood. We interrogated FCMR contributions to B cell function by studying mice that lack FCMR. FCMR transcripts are expressed at different levels by various B cell subsets. FCMR-deficient mice have reduced numbers of developing B cells, splenic follicular and peritoneal B-2 cells, but increased levels of peritoneal B-1a cells and autoantibodies. After immunization, germinal center B cell and plasma cell numbers are increased. FCMR-deficient B cells are sensitive to apoptosis induced by BCR ligation. Our studies demonstrate that FCMR is required for B cell differentiation and homeostasis, the prevention of autoreactive B cells, and responsiveness to antigenic challenge.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    RVK:
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    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2013
    detail.hit.zdb_id: 1475085-5
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  • 7
    Online Resource
    Online Resource
    The American Association of Immunologists ; 2009
    In:  The Journal of Immunology Vol. 183, No. 5 ( 2009-09-01), p. 3188-3194
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 183, No. 5 ( 2009-09-01), p. 3188-3194
    Abstract: IFN regulatory factor 8 (IRF8) is a transcription factor that affects the differentiation and function of myeloid, dendritic, and B cells. Herein we report that IRF8 regulates the expression of Mdm2, a suppressor of p53-dependent and -independent apoptosis pathways, in germinal center (GC) B cells. In GC B cells of IRF8-deficient mice, Mdm2 transcripts were greatly down-regulated, and MDM2 protein was poorly expressed in GC of Irf8−/− mice. Small interfering RNA-induced repression of IRF8 in a GC-derived B cell line resulted in decreased expression of MDM2 at the protein level but increased expression of p53 and p21. We found that IRF8 binds to the Mdm2 P2 promoter, and that cotransfection of an IRF8 expression vector with an Mdm2 reporter construct stimulated significant increases in reporter activity. Additionally, transcripts of the p53 target Pmaip1 (Noxa) were significantly increased in IRF8-deficient GC B cells as well as in the IRF8 knockdown B cell line. Finally, cells deficient in IRF8 exhibited growth suppression and increased sensitivity to apoptosis induced by etoposide or IL-21. These results suggest that by regulating MDM2, IRF8 might allow GC B cells to tolerate physiological DNA breaks that otherwise would trigger apoptosis.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
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    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2009
    detail.hit.zdb_id: 1475085-5
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  • 8
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 193, No. 4 ( 2014-08-15), p. 1766-1777
    Abstract: The IFN regulatory factor family member 8 (IRF8) regulates differentiation of lymphoid and myeloid lineage cells by promoting or suppressing lineage-specific genes. How IRF8 promotes hematopoietic progenitors to commit to one lineage while preventing the development of alternative lineages is not known. In this study, we report an IRF8–EGFP fusion protein reporter mouse that revealed previously unrecognized patterns of IRF8 expression. Differentiation of hematopoietic stem cells into oligopotent progenitors is associated with progressive increases in IRF8-EGFP expression. However, significant induction of IRF8-EGFP is found in granulocyte–myeloid progenitors and the common lymphoid progenitors but not the megakaryocytic–erythroid progenitors. Surprisingly, IRF8-EGFP identifies three subsets of the seemingly homogeneous granulocyte–myeloid progenitors with an intermediate level of expression of EGFP defining bipotent progenitors that differentiation into either EGFPhi monocytic progenitors or EGFPlo granulocytic progenitors. Also surprisingly, IRF8-EGFP revealed a highly heterogeneous pre–pro-B population with a fluorescence intensity ranging from background to 4 orders above background. Interestingly, IRF8–EGFP readily distinguishes true B cell committed (EGFPint) from those that are noncommitted. Moreover, dendritic cell progenitors expressed extremely high levels of IRF8-EGFP. Taken together, the IRF8-EGFP reporter revealed previously unrecognized subsets with distinct developmental potentials in phenotypically well-defined oligopotent progenitors, providing new insights into the dynamic heterogeneity of developing hematopoietic progenitors.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
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    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2014
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  • 9
    Online Resource
    Online Resource
    The American Association of Immunologists ; 2019
    In:  The Journal of Immunology Vol. 202, No. 1_Supplement ( 2019-05-01), p. 123.1-123.1
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 202, No. 1_Supplement ( 2019-05-01), p. 123.1-123.1
    Abstract: The Ets family member PU.1 and the IRF family member IRF8 play crucial roles in regulating hematopoietic cell development including B cells. Both factors are constitutively expressed at high levels in B cells and control plasma cell differentiation. IRF8 and PU.1 function either together as a heterodimer or by pairing with other factors to bind target DNA sequences. Several consensus binding sequences for IRF8 and PU.1 have been identified, including the canonical interferon stimulated response element (ISRE) sequence motif (GAAANNGAAA), the Ets-IRF composite element (EICE) (GGAANNGAAA) and the IRF-Ets composite sequence (IECS) (GAAANN[N]GGAA). Although the target genes of IRF8 and PU.1 have been studied previously by chromatin immunoprecipitation (ChIP), the nature and the importance of the motifs engaging both PU.1 and IRF8 in B cells have not been determined. In this study, we performed ChIP-seq using sort-purified naïve follicular B cells from C57BL/6 mice that were either not stimulated or stimulated with anti-IgM plus anti-CD40, which mimic signals for germinal center B cell differentiation. We also integrated our ChIP-seq data with RNA-seq data from B cells deficient for both IRF8 and PU.1, and found that IRF8 and PU.1 regulate gene expression by preferentially binding to the EICE motifs of target genes known to maintain follicular B cell identity, localization, and survival. In contrast, in activated B cells, the binding landscape of IRF8/PU.1 in target genes shifts to IRF8-dominant ISRE motifs, possibly due to elevated expression of IRF8. These results provide new insights into our understanding of the molecular mechanisms underlying the transcriptional control of late stage B cell development.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    RVK:
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    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2019
    detail.hit.zdb_id: 1475085-5
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  • 10
    Online Resource
    Online Resource
    The American Association of Immunologists ; 2006
    In:  The Journal of Immunology Vol. 177, No. 5 ( 2006-09-01), p. 2793-2802
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 177, No. 5 ( 2006-09-01), p. 2793-2802
    Abstract: EBV is associated with systemic lupus erythematosus (SLE), but how it might contribute to the etiology is not clear. Since EBV-encoded latent membrane protein 2A (LMP2A) interferes with normal B cell differentiation and function, we sought to determine its effect on B cell tolerance. Mice transgenic for both LMP2A and the Ig transgene 2-12H specific for the ribonucleoprotein Smith (Sm), a target of the immune system in SLE, develop a spontaneous anti-Sm response. LMP2A allows anti-Sm B cells to overcome the regulatory checkpoint at the early preplasma cell stage by a self-Ag-dependent mechanism. LMP2A induces a heightened sensitivity to TLR ligand stimulation, resulting in increased proliferation or Ab-secreting cell differentiation or both. Thus, we propose a model whereby LMP2A induces hypersensitivity to TLR stimulation, leading to activation of anti-Sm B cells through the BCR/TLR pathway. These data further implicate TLRs in the etiology of SLE and suggest a mechanistic link between EBV infection and SLE.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    RVK:
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    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2006
    detail.hit.zdb_id: 1475085-5
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