技术资料

B cells play an important role in type 1 diabetes (T1D) development. However,the role of B cell activation-induced cytidine deaminase (AID) in diabetes development is not clear. We hypothesized that AID is important in the immunopathogenesis of T1D. To test this hypothesis,we generated AID-deficient (AID-/-) NOD mice. We found that AID-/-NOD mice developed accelerated T1D,with worse insulitis and high levels of anti-insulin autoantibody in the circulation. Interestingly,neither maternal IgG transferred through placenta,nor IgA transferred through milk affected the accelerated diabetes development. AID-/-NOD mice showed increased activation and proliferation of B and T cells. We found enhanced T-B cell interactions in AID-/-NOD mice,with increased T-bet and IFN-γ expression in CD4+ T cells in the presence of AID-/- B cells. Moreover,excessive lymphoid expansion was observed in AID-/-NOD mice. Importantly,antigen-specific BDC2.5 CD4+ T cells caused more rapid onset of diabetes when cotransferred with AID-/- B cells than when cotransferred with AID+/+ B cells. Thus,our study provides insights into the role of AID in T1D. Our data also suggest that AID is a negative regulator of immune tolerance and ablation of AID can lead to exacerbated islet autoimmunity and accelerated T1D development. View Publication

B cell dysregulation in aging is thought to mostly occur in conventional B2 cells without affecting innate B1 cells. Elderly humans and mice also accumulate 4-1BBL(+)MHC class-I(Hi)CD86(Hi)B cells of unknown origin. In this article,we report that these cells,termed 4BL cells,are activated murine and possibly human B1a cells. The activation is mediated by aging human monocytes and murine peritoneal macrophages. They induce expression and activation of 4-1BBL and IFN-γR1 on B1a cells to subsequently upregulate membrane TNF-α and CD86. As a result,activated B1a/4BL cells induce expression of granzyme B in CD8(+)T cells by targeting TNFR2 via membrane TNF-α and providing costimulation with CD86. Thus,for the first time,to our knowledge,these results indicate that aging affects the function of B1a cells. Upon aging,these cells lose their tumor-supporting activity and become inducers of potentially antitumor and autoimmune CD8(+)T cells. View Publication

The B-cell receptor (BCR) transmits life and death signals throughout B-cell development,and altered BCR signaling may be required for survival of B-lymphoma cells. We used single-cell signaling profiles to compare follicular lymphoma (FL) B cells and nonmalignant host B cells within individual patient biopsies and identified BCR-mediated signaling events specific to lymphoma B cells. Expression of CD20,Bcl-2,and BCR light chain isotype (kappa or lambda) distinguished FL tumor B-cell and nontumor host B-cell subsets within FL patient biopsies. BCR-mediated signaling via phosphorylation of Btk,Syk,Erk1/2,and p38 occurred more rapidly in tumor B cells from FL samples than in infiltrating nontumor B cells,achieved greater levels of per-cell signaling,and sustained this level of signaling for hours longer than nontumor B cells. The timing and magnitude of BCR-mediated signaling in nontumor B cells within an FL sample instead resembled that observed in mature B cells from the peripheral blood of healthy subjects. BCR signaling pathways that are potentiated specifically in lymphoma cells should provide new targets for therapeutic attention. View Publication

The mutagenic enzyme activation-induced cytidine deaminase (AID) is required for immunoglobulin class switch recombination (CSR) and somatic hypermutation (SHM) in germinal center (GC) B cells. Deregulated expression of AID is associated with various B-cell malignancies and,currently,it remains unclear how AID activity is extinguished to avoid illegitimate mutations. AID has also been shown to be alternatively spliced in malignant B cells,and there is limited evidence that this also occurs in normal blood B cells. The functional significance of these splice variants remains unknown. Here we show that normal GC human B cells and blood memory B cells similarly express AID splice variants and show for the first time that AID splicing variants are singly expressed in individual normal B cells as well as malignant B cells from chronic lymphocytic leukemia patients. We further demonstrate that the alternative AID splice variants display different activities ranging from inactivation of CSR to inactivation or heightened SHM activity. Our data therefore suggest that CSR and SHM are differentially switched off by varying the expression of splicing products of AID at the individual cell level. Most importantly,our findings suggest a novel tumor suppression mechanism by which unnecessary AID mutagenic activities are promptly contained for GC B cells. View Publication

The aryl hydrocarbon receptor (AhR),a transcription factor known for mediating xenobiotic toxicity,is expressed in B cells,which are known targets for environmental pollutants. However,it is unclear what the physiological functions of AhR in B cells are. We show here that expression of Ahr in B cells is up-regulated upon B-cell receptor (BCR) engagement and IL-4 treatment. Addition of a natural ligand of AhR,FICZ,induces AhR translocation to the nucleus and transcription of the AhR target gene Cyp1a1,showing that the AhR pathway is functional in B cells. AhR-deficient (Ahr(-/-)) B cells proliferate less than AhR-sufficient (Ahr(+/+)) cells following in vitro BCR stimulation and in vivo adoptive transfer models confirmed that Ahr(-/-) B cells are outcompeted by Ahr(+/+) cells. Transcriptome comparison of AhR-deficient and AhR-sufficient B cells identified cyclin O (Ccno),a direct target of AhR,as a top candidate affected by AhR deficiency. View Publication

Multiple sclerosis (MS) is caused by T cells that are reactive for brain antigens. In experimental autoimmune encephalomyelitis,the animal model for MS,myelin-reactive T cells initiate the autoimmune process when entering the nervous tissue and become reactivated upon local encounter of their cognate CNS antigen. Thereby,the strength of the T-cellular reactivation process within the CNS tissue is crucial for the manifestation and the severity of the clinical disease. Recently,B cells were found to participate in the pathogenesis of CNS autoimmunity,with several diverse underlying mechanisms being under discussion. We here report that B cells play an important role in promoting the initiation process of CNS autoimmunity. Myelin-specific antibodies produced by autoreactive B cells after activation in the periphery diffused into the CNS together with the first invading pathogenic T cells. The antibodies accumulated in resident antigen-presenting phagocytes and significantly enhanced the activation of the incoming effector T cells. The ensuing strong blood-brain barrier disruption and immune cell recruitment resulted in rapid manifestation of clinical disease. Therefore,myelin oligodendrocyte glycoprotein (MOG)-specific autoantibodies can initiate disease bouts by cooperating with the autoreactive T cells in helping them to recognize their autoantigen and become efficiently reactivated within the immune-deprived nervous tissue. View Publication

The immunodeficiency disorder,X-linked agammaglobulinemia (XLA),results from mutations in the gene encoding Bruton tyrosine kinase (Btk). Btk is required for pre-B cell clonal expansion and B-cell antigen receptor signaling. XLA patients lack mature B cells and immunoglobulin and experience recurrent bacterial infections only partially mitigated by life-long antibody replacement therapy. In pursuit of definitive therapy for XLA,we tested ex vivo gene therapy using a lentiviral vector (LV) containing the immunoglobulin enhancer (Emu) and Igbeta (B29) minimal promoter to drive B lineage-specific human Btk expression in Btk/Tec(-/-) mice,a strain that reproduces the features of human XLA. After transplantation of EmuB29-Btk-LV-transduced stem cells,treated mice showed significant,albeit incomplete,rescue of mature B cells in the bone marrow,peripheral blood,spleen,and peritoneal cavity,and improved responses to T-independent and T-dependent antigens. LV-treated B cells exhibited enhanced B-cell antigen receptor signaling and an in vivo selective advantage in the peripheral versus central B-cell compartment. Secondary transplantation showed sustained Btk expression,viral integration,and partial functional responses,consistent with long-term stem cell marking; and serial transplantation revealed no evidence for cellular or systemic toxicity. These findings strongly support pursuit of B lineage-targeted LV gene therapy in human XLA. View Publication

The tumor necrosis factor (TNF)-like ligand BAFF/BLyS (B-cell activating factor of the TNF family/B-lymphocyte stimulator) is a potent B-cell survival factor,yet its functional relationship with other B-cell surface molecules such as CD19 and CD40 is poorly understood. We found that follicular dendritic cells (FDCs) in human lymph nodes expressed BAFF abundantly. BAFF up-regulated a B cell-specific transcription factor Pax5/BSAP (Pax5/B cell-specific activator protein) activity and its target CD19,a major component of the B-cell coreceptor complex,and synergistically enhanced CD19 phosphorylation by B-cell antigen receptor (BCR). BAFF further enhanced B-cell proliferation,immunoglobulin G (IgG) production,and reactivity to CD154 by BCR/CD19 coligation and interleukin-15 (IL-15). Our results suggest that BAFF may play an important role in FDC-B-cell interactions through the B-cell coreceptor complex and a possibly sequential link between the T cell-independent and -dependent B-cell responses in the germinal centers. View Publication

Primary systemic amyloidosis (AL) is a rare monoclonal plasma cell (PC) disorder characterized by the deposition of misfolded immunoglobulin (Ig) light chains (LC) in vital organs throughout the body. To our knowledge,no cell lines have ever been established from AL patients. Here we describe the establishment of the ALMC-1 and ALMC-2 cell lines from an AL patient. Both cell lines exhibit a PC phenotype and display cytokine-dependent growth. Using a comprehensive genetic approach,we established the genetic relationship between the cell lines and the primary patient cells,and we were also able to identify new genetic changes accompanying tumor progression that may explain the natural history of this patient's disease. Importantly,we demonstrate that free lambda LC secreted by both cell lines contained a beta structure and formed amyloid fibrils. Despite absolute Ig LC variable gene sequence identity,the proteins show differences in amyloid formation kinetics that are abolished by the presence of Na(2)SO(4). The formation of amyloid fibrils from these naturally secreting human LC cell lines is unprecedented. Moreover,these cell lines will provide an invaluable tool to better understand AL,from the combined perspectives of amyloidogenic protein structure and amyloid formation,genetics,and cell biology. View Publication

According to the current model of adult hematopoiesis,differentiation of pluripotential hematopoietic stem cells into common myeloid- and lymphoid-committed progenitors establishes an early separation between the myeloid and lymphoid lineages. This report describes a rare and previously unidentified CD45R-CD19+ B cell progenitor population in postnatal bone marrow that can also generate macrophages. In addition to the definition of this B-lineage intermediate,the data indicate that a developmental relationship between the B and macrophage lineages is retained during postnatal hematopoiesis. View Publication