技术资料

B lymphocyte stimulator (BLyS) is a well-known direct costimulator of adaptive immune cells,particularly B lineage cells. However,we have reported recently that BLyS is also able to activate monocytes. Other innate immune cells,such as dendritic cells (DCs),play a key role in the initiation of adaptive immune responses and the purpose of the current study was to assess whether there is a direct role for BLyS in modulating human DC functions. In this study,we show that BLyS induces DC activation and maturation. Thus,BLyS strongly induced up-regulation of surface costimulatory molecule expression and secretion of specific cytokines and chemokines in DCs. BLyS-stimulated DCs (BLyS-DCs) were also able to augment allogeneic CD4 T cell proliferation to a greater extent than control DCs. BLyS-DCs secreted elevated levels of the major Th1-polarizing cytokine,IL-12p70,and they promoted naive CD4 T cell differentiation into Th1 T cells. Regarding BLyS receptor expression,DCs primarily express cytoplasmic transmembrane activator and CAML interactor; however,low levels of cell surface transmembrane activator and CAML interactor are expressed as well. Collectively,our data suggest that BLyS may modulate adaptive immune cells indirectly by inducing DC maturation. View Publication

The dynamic interplay between dendritic cells (DCs) and human immunodeficiency virus type-1 (HIV-1) is thought to result in viral dissemination and evasion of antiviral immunity. Although initial observations suggested that the C-type lectin receptor (CLR) DC-SIGN was responsible for the trans-infection function of the virus,subsequent studies demonstrated that trans-infection of CD4(+) T cells with HIV-1 can also occur through DC-SIGN-independent mechanisms. We demonstrate that a cell surface molecule designated DCIR (for DC immunoreceptor),a member of a recently described family of DC-expressing CLRs,can participate in the capture of HIV-1 and promote infection in trans and in cis of autologous CD4(+) T cells from human immature monocyte-derived DCs. The contribution of DCIR to these processes was revealed using DCIR-specific siRNAs and a polyclonal antibody specific for the carbohydrate recognition domain of DCIR. Data from transfection experiments indicated that DCIR acts as a ligand for HIV-1 and is involved in events leading to productive virus infection. Finally,we show that the neck domain of DCIR is important for the DCIR-mediated effect on virus binding and infection. These results point to a possible role for DCIR in HIV-1 pathogenesis by supporting the productive infection of DCs and promoting virus propagation. View Publication

Umbilical cord blood (UCB) is increasingly being used for human hematopoietic stem cell (HSC) transplantation in children but often requires pooling multiple cords to obtain sufficient numbers for transplantation in adults. To overcome this limitation,we have used an ex vivo two-week culture system to expand the number of hematopoietic CD34(+) cells in cord blood. To assess the in vivo function of these expanded CD34(+) cells,cultured human UCB containing 1 x 10(6) CD34(+) cells were transplanted into conditioned NOD-scid IL2rgamma(null) mice. The expanded CD34(+) cells displayed short- and long-term repopulating cell activity. The cultured human cells differentiated into myeloid,B-lymphoid,and erythroid lineages,but not T lymphocytes. Administration of human recombinant TNFalpha to recipient mice immediately prior to transplantation promoted human thymocyte and T-cell development. These T cells proliferated vigorously in response to TCR cross-linking by anti-CD3 antibody. Engrafted TNFalpha-treated mice generated antibodies in response to T-dependent and T-independent immunization,which was enhanced when mice were co-treated with the B cell cytokine BLyS. Ex vivo expanded CD34(+) human UCB cells have the capacity to generate multiple hematopoietic lineages and a functional human immune system upon transplantation into TNFalpha-treated NOD-scid IL2rgamma(null) mice. View Publication

The presence of interleukin-2 (IL-2)-producing human immunodeficiency virus type 1 (HIV-1)-specific CD4(+) T-cell responses has been associated with the immunological control of HIV-1 replication; however,the causal relationship between these factors remains unclear. Here we show that IL-2-producing HIV-1-specific CD4(+) T cells can be cloned from acutely HIV-1-infected individuals. Despite the early presence of these cells,each of the individuals in the present study exhibited progressive disease,with one individual showing rapid progression. In this rapid progressor,three IL-2-producing HIV-1 Gag-specific CD4(+) T-cell responses were identified and mapped to the following optimal epitopes: HIVWASRELER,REPRGSDIAGT,and FRDYVDRFYKT. Responses to these epitopes in peripheral blood mononuclear cells were monitored longitudinally to textgreater1 year postinfection,and contemporaneous circulating plasma viruses were sequenced. A variant of the FRDYVDRFYKT epitope sequence,FRDYVDQFYKT,was observed in 1/21 plasma viruses sequenced at 5 months postinfection and 1/10 viruses at 7 months postinfection. This variant failed to stimulate the corresponding CD4(+) T-cell clone and thus constitutes an escape mutant. Responses to each of the three Gag epitopes were rapidly lost,and this loss was accompanied by a loss of antigen-specific cells in the periphery as measured by using an FRDYVDRFYKT-presenting major histocompatibility complex class II tetramer. Highly active antiretroviral therapy was associated with the reemergence of FRDYVDRFYKT-specific cells by tetramer. Thus,our data support that IL-2-producing HIV-1-specific CD4(+) T-cell responses can exert immune pressure during early HIV-1 infection but that the inability of these responses to enforce enduring control of viral replication is related to the deletion and/or dysfunction of HIV-1-specific CD4(+) T cells rather than to the fixation of escape mutations at high frequencies. View Publication

Small intestinal CD103(+) dendritic cells (DCs) have the selective ability to promote de novo generation of regulatory T cells via the production of retinoic acid (RA). Considering that aldehyde dehydrogenase (ALDH) activity controls the production of RA,we used a flow cytometry-based assay to measure ALDH activity at the single-cell level and to perform a comprehensive analysis of the RA-producing DC populations present in lymphoid and nonlymphoid mouse tissues. RA-producing DCs were primarily of the tissue-derived,migratory DC subtype and can be readily found in the skin and in the lungs as well as in their corresponding draining lymph nodes. The RA-producing skin-derived DCs were capable of triggering the generation of regulatory T cells,a finding demonstrating that the presence of RA-producing,tolerogenic DCs is not restricted to the intestinal tract as previously thought. Unexpectedly,the production of RA by skin DCs was restricted to CD103(-) DCs,indicating that CD103 expression does not constitute a universal" marker for RA-producing mouse DCs. Finally� View Publication

The development of mature blood cells from hematopoietic stem cells requires coordinated activities of transcriptional networks. Transcriptional repressor growth factor independence 1 (Gfi-1) is required for the development of B cells,T cells,neutrophils,and for the maintenance of hematopoietic stem cell function. However,the mechanisms by which Gfi-1 regulates hematopoiesis and how Gfi-1 integrates into transcriptional networks remain unclear. Here,we provide evidence that Id2 is a transcriptional target of Gfi-1,and repression of Id2 by Gfi-1 is required for B-cell and myeloid development. Gfi-1 binds to 3 conserved regions in the Id2 promoter and represses Id2 promoter activity in transient reporter assays. Increased Id2 expression was observed in multipotent progenitors,myeloid progenitors,T-cell progenitors,and B-cell progenitors in Gfi-1(-/-) mice. Knockdown of Id2 expression or heterozygosity at the Id2 locus partially rescues the B-cell and myeloid development but not the T-cell development in Gfi-1(-/-) mice. These studies demonstrate a role of Id2 in mediating Gfi-1 functions in B-cell and myeloid development and provide a direct link between Gfi-1 and the B-cell transcriptional network by its ability to repress Id2 expression. View Publication