技术资料

It is unknown how dendritic cells (DCs) become specialized as mucosal DCs and maintain intestinal homeostasis. We report that a subset of bone marrow cells freshly isolated from C57BL/6 mice express the retinoic acid (RA)-synthesizing enzyme aldehyde dehydrogenase family 1,subfamily A2 (ALDH1a2) and are capable of providing RA to DC precursors in the bone marrow microenvironment. RA induced bone marrow-derived DCs to express CCR9 and ALDH1a2 and conferred upon them mucosal DC functions,including induction of Foxp3(+) regulatory T cells,IgA-secreting B cells,and gut-homing molecules. This response of DCs to RA was dependent on a narrow time window and stringent dose effect. RA promoted bone marrow-derived DC production of bioactive TGF-β by inhibiting suppressor of cytokine signaling 3 expression and thereby enhancing STAT3 activation. These RA effects were evident in vivo,in that mucosal DCs from vitamin A-deficient mice had reduced mucosal DC function,namely failure to induce Foxp3(+) regulatory T cells. Furthermore,MyD88 signaling enhanced RA-educated DC ALDH1a2 expression and was required for optimal TGF-β production. These data indicate that RA plays a critical role in the generation of mucosal DCs from bone marrow and in their functional activity. View Publication

In view of recent reports documenting pervasive translation outside of canonical protein-coding sequences,we wished to determine the proportion of major histocompatibility complex (MHC) class I-associated peptides (MAPs) derived from non-canonical reading frames. Here we perform proteogenomic analyses of MAPs eluted from human B cells using high-throughput mass spectrometry to probe the six-frame translation of the B-cell transcriptome. We report that ∼ 10% of MAPs originate from allegedly noncoding genomic sequences or exonic out-of-frame translation. The biogenesis and properties of these 'cryptic MAPs' differ from those of conventional MAPs. Cryptic MAPs come from very short proteins with atypical C termini,and are coded by transcripts bearing long 3'UTRs enriched in destabilizing elements. Relative to conventional MAPs,cryptic MAPs display different MHC class I-binding preferences and harbour more genomic polymorphisms,some of which are immunogenic. Cryptic MAPs increase the complexity of the MAP repertoire and enhance the scope of CD8 T-cell immunosurveillance. View Publication

Retinoic acid (RA) produced by intestinal dendritic cells (DCs) imprints gut-homing specificity on lymphocytes and enhances Foxp3(+) regulatory T-cell differentiation. The expression of aldehyde dehydrogenase (ALDH) 1A in these DCs is essential for the RA production. However,it remains unclear how the steady-state ALDH1A expression is induced under specific pathogen-free (SPF) conditions. Here,we found that bone marrow-derived dendritic cells (BM-DCs) generated with granulocyte-macrophage colony-stimulating factor (GM-CSF) expressed Aldh1a2,an isoform of Aldh1a,but that fms-related tyrosine kinase 3 ligand-generated BM-DCs did not. DCs from mesenteric lymph nodes (MLN) and Peyer's patches (PP) of normal SPF mice expressed ALDH1A2,but not the other known RA-producing enzymes. Employing a flow cytometric method,we detected ALDH activities in 10-30% of PP-DCs and MLN-DCs. They were CD11c(high)CD4(-/low)CD8alpha(intermediate)CD11b(-/low) F4/80(low/intermediate)CD45RB(low)CD86(high)MHC class II(high)B220(-)CD103(+). Equivalent levels of aldehyde dehydrogenase activity (ALDHact) and ALDH1A2 expression were induced synergistically by GM-CSF and IL-4 in splenic DCs in vitro. In BM-DCs,however,additional signals via Toll-like receptors or RA receptors were required for inducing the equivalent levels. The generated ALDH1A2(+) DCs triggered T cells to express gut-homing receptors or Foxp3. GM-CSF receptor-deficient or vitamin A-deficient mice exhibited marked reductions in the ALDHact in intestinal DCs and the T cell number in the intestinal lamina propria,whereas IL-4 receptor-mediated signals were dispensable. GM-CSF(+)CD11c(-)F4/80(+) cells existed constitutively in the intestinal tissues. The results suggest that GM-CSF and RA itself are pivotal among multiple microenvironment factors that enable intestinal DCs to produce RA. View Publication

Histone deacetylase inhibitors (HdI) could potentially improve the differentiation of leukemic dendritic cells (DC). Therefore,bone marrow samples from 100 children with acute lymphoblastic leukemia (ALL) were cultured in the cytokines TNF-alpha,GM-CSF,c-kit ligand,and fetal liver tyrosine kinase 3 ligand,with or without IL-3 and -4 and after administration of HdI valproic acid (VAL),suberoylanilide hydroxamic acid (SAHA),isobutyramid,or trichostatin A. Among the tested samples,25 were positive for the chromosomal translocation t(12;21),encoding the fusion gene translocation ETS-like leukemia/acute myeloid leukemia 1 (TEL/AML1). SAHA increased CD83 expression of TEL/AML1-positive blasts in conditions without ILs,and SAHA and VAL increased the number of CD86(+)80(-) cells in the presence of ILs. VAL and isobutyramid supported the allostimulatory capacities of TEL/AML1-positive,leukemic DC; VAL and SAHA reduced those of TEL/AML1-negative DC. Cytotoxic T cells sensitized with leukemic DC produced more IFN-gamma and TNF-alpha upon presentation of the TEL/AML1 peptide. They also induced the cytotoxic lysis of nondifferentiated blasts,which was enhanced when TEL/AML1-positive DC had developed after addition of VAL or SAHA. Therefore,the use of HdI in the differentiation of leukemic DC from patients with TEL/AML1-positive ALL is recommended. View Publication

HIV-1 infection leads to numerous B cell abnormalities,including hypergammaglobulinemia,nonspecific B cell activation,nonspecific class switching,increased cell turnover,breakage of tolerance,increased immature/transitional B cells,B cell malignancies,as well as a loss of capacity to generate and maintain memory,all of which contribute to a global impairment of the immune humoral compartment. Several cytokines and soluble factors,which are increased in sera of HIV-1-infected individuals,have been suggested to directly or indirectly contribute to these B cell dysfunctions,and one of these is the B cell-activating factor (BAFF). We report in this study that HIV-1 (X4- and R5-tropic) upregulates BAFF expression and secretion by human monocytes. Moreover,we show that the virus-mediated production of BAFF by monocytes relies on a type I IFN response by a small percentage of plasmacytoid dendritic cells (pDCs) present in the monocyte cultures. HIV-1-induced type I IFN by pDCs triggers BAFF production in both classical and intermediate monocytes,but not in nonclassical monocytes,which nonetheless display a very strong basal BAFF production. We report also that basal BAFF secretion was higher in monocytes obtained from females compared with those from male donors. This study provides a novel mechanistic explanation for the increased BAFF levels observed during HIV-1 infection and highlights the importance of pDC/monocyte crosstalk to drive BAFF secretion. View Publication

Plasmacytoid dendritic cells (pDCs) are innate sensors of viral infections and important mediators of antiviral innate immunity through their ability to produce large amounts of IFN-α. Moreover,Toll-like receptor 7 (TLR7) and 9 (TLR9) ligands,such as HIV and CpG respectively,turn pDCs into TRAIL-expressing killer pDCs able to lyse HIV-infected CD4+ T cells. NK cells can regulate antiviral immunity by modulating pDC functions,and pDC production of IFN-α as well as cell-cell contact is required to promote NK cell functions. Impaired pDC-NK cell crosstalk was reported in the setting of HIV-1 infection,but the impact of HIV-1 on TRAIL expression and innate antiviral immunity during this crosstalk is unknown. Here,we report that low concentrations of CCR5-tropic HIV-1Ba-L promote the release of pro-inflammatory cytokines such as IFN-α,TNF-α,IFN-γ and IL-12,and CCR5-interacting chemokines (MIP-1α and MIP-1β) in NK-pDCs co-cultures. At high HIV-1BaL concentrations,the addition of NK cells did not promote the release of these mediators,suggesting that once efficiently triggered by the virus,pDCs could not integrate new activating signals delivered by NK cells. However,high HIV-1BaL concentrations were required to trigger IFN-α-mediated TRAIL expression at the surface of both pDCs and NK cells during their crosstalk. Interestingly,we identified the alarmin HMGB1,released at pDC-NK cell synapse,as an essential trigger for the secretion of IFN-α and IFN-related soluble mediators during the interplay of HIV-1 exposed pDCs with NK cells. Moreover,HMGB1 was found crucial for mTRAIL translocation to the plasma membrane of both pDCs and NK cells during their crosstalk following pDC exposure to HIV-1. Data from serum analyses of circulating HMGB1,HMGB1-specific antibodies,sTRAIL and IP-10 in a cohort of 67 HIV-1+ patients argue for the in vivo relevance of these observations. Altogether,these findings identify HMGB1 as a trigger for IFN-α-mediated TRAIL expression at the surface of pDCs and NK cells,and they suggest a novel mechanism of innate control of HIV-1 infection. View Publication