技术资料

HIV elite controllers (EC) are a rare group of HIV-infected patients who are able to maintain undetectable viral loads during a long period of time in the absence of antiretroviral treatment. Adaptive immunity and host genetic factors,although implicated,do not entirely explain this phenomenon. On the other hand,plasmacytoid dendritic cells (pDCs) are the principal type I interferon (IFN) producers in response to viral infection,and it is unknown whether pDCs are involved in the control of HIV infection in EC. In our study,we analyzed peripheral pDC levels and IFN-α production by peripheral blood mononuclear cells (PBMCs) in EC compared to other groups of HIV-infected patients,the ability of pDCs to reduce HIV production in vitro,and the mechanisms potentially involved. We showed preserved pDC counts and IFN-α production in EC. We also observed a higher capacity of pDCs from EC to reduce HIV production and to induce T cell apoptosis,whereas pDCs from viremic patients barely responded without previous Toll-like receptor 9 (TLR-9) stimulus. The preserved functionality of pDCs from EC to reduce viral production may be one of the mechanisms involved in the control of HIV viremia in these subjects. These results demonstrate the importance of innate immunity in HIV pathogenesis,and an understanding of pDC mechanisms would be helpful for the design of new therapies. View Publication

New vaccines against pertussis are needed to evoke full protection and long-lasting immunological memory starting from the first administration in neonates--the major target of the life-threatening pertussis infection. A novel live attenuated Bordetella pertussis vaccine strain,BPZE1,has been developed by eliminating or detoxifying three important B. pertussis virulence factors: pertussis toxin,dermonecrotic toxin,and tracheal cytotoxin. We used a human preclinical ex vivo model based on monocyte-derived dendritic cells (MDDCs) to evaluate BPZE1 immunogenicity. We studied the effects of BPZE1 on MDDC functions,focusing on the impact of Bordetella-primed dendritic cells in the regulation of Th and suppressor T cells (Ts). BPZE1 is able to activate human MDDCs and to promote the production of a broad spectrum of proinflammatory and regulatory cytokines. Moreover,conversely to its parental wild-type counterpart BPSM,BPZE1-primed MDDCs very efficiently migrate in vitro in response to the lymphatic chemokine CCL21,due to the inactivation of pertussis toxin enzymatic activity. BPZE1-primed MDDCs drove a mixed Th1/Th17 polarization and also induced functional Ts. Experiments performed in a Transwell system showed that cell contact rather than the production of soluble factors was required for suppression activity. Overall,our findings support the potential of BPZE1 as a novel live attenuated pertussis vaccine,as BPZE1-challenged dendritic cells might migrate from the site of infection to the lymph nodes,prime Th cells,mount an adaptive immune response,and orchestrate Th1/Th17 and Ts responses. View Publication

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 mouse,a subset of dendritic cells (DCs) known as CD8alpha+ DCs has emerged as an important player in the regulation of T cell responses and a promising target in vaccination strategies. However,translation into clinical protocols has been hampered by the failure to identify CD8alpha+ DCs in humans. Here,we characterize a population of human DCs that expresses DNGR-1 (CLEC9A) and high levels of BDCA3 and resembles mouse CD8alpha+ DCs in phenotype and function. We describe the presence of such cells in the spleens of humans and humanized mice and report on a protocol to generate them in vitro. Like mouse CD8alpha+ DCs,human DNGR-1+ BDCA3hi DCs express Necl2,CD207,BATF3,IRF8,and TLR3,but not CD11b,IRF4,TLR7,or (unlike CD8alpha+ DCs) TLR9. DNGR-1+ BDCA3hi DCs respond to poly I:C and agonists of TLR8,but not of TLR7,and produce interleukin (IL)-12 when given innate and T cell-derived signals. Notably,DNGR-1+ BDCA3+ DCs from in vitro cultures efficiently internalize material from dead cells and can cross-present exogenous antigens to CD8+ T cells upon treatment with poly I:C. The characterization of human DNGR-1+ BDCA3hi DCs and the ability to grow them in vitro opens the door for exploiting this subset in immunotherapy. View Publication

Recently,it has been shown that certain combinations of TLR ligands act in synergy to induce the release of IL-12 by DCs. In this study,we sought to define the critical parameters underlying TLR synergy. Our data show that TLR ligands act synergistically if MyD88- and TRIF-dependent ligands are combined. TLR4 uses both of these adaptor molecules,thus activation via TLR4 proved to be a synergistic event on its own. TLR synergy did not affect all aspects of DC activation but enhanced primarily the release of certain cytokines,particularly IL-12,whereas the expression of costimulatory molecules remained unchanged. Consequently,synergistic activation of DC did not affect their ability to induce T cell proliferation but resulted in T(H)1-biased responses in vitro and in vivo. Furthermore,we examined the impact of TLR ligand combinations on primary DC in vitro but observed only modest effects with a combination of CpG + Poly (I:C). However,noticeable synergy in terms of IL-12 production by DCs was detectable in vivo after systemic administration of CpG + Poly (I:C). Finally,we show that synergy is partially dependent on IFNAR signaling but does not require the release of IFNs to the enviroment,suggesting an autocrine action of type I IFNs. View Publication

The type-III interferon (IFN) family is composed of 3 molecules in humans: IFN-lambda1 (interleukin-29 [IL-29]),IFN-lambda2 (IL-28A),and IFN-lambda3 (IL-28B),each of which signals through the same receptor complex. Plasmacytoid dendritic cells (pDCs) are major IFN-lambda producers among peripheral lymphocytes. Recently,it has been shown that IFN-lambda1 exerts a powerful inhibitory effect over the T-helper 2 (Th2) response by antagonizing the effect of IL-4 on CD4(+) T cells and inhibiting the production of Th2-associated cytokines. Here,we asked whether Th2 cytokines exert reciprocal control over IFN-lambda production. IL-4 treatment during stimulation of human peripheral lymphocytes significantly elevated IFN-lambda1 transcription and secretion. However,pDCs were not directly responsive to IL-4. Using depletion and reconstitution experiments,we showed that IL-4-responsive monocytes are an intermediary cell,responding to IL-4 by elevating their secretion of IL-1 receptor antagonist (IL-Ra); this IL-1Ra acts on pDCs to elevate their IFN-lambda1 output. Thus,our experiments revealed a novel mechanism for regulation of both IFN-lambda1 production and pDC function,and suggests an expanded immunomodulatory role for Th2-associated cytokines. 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

Chemokine receptor CX3CR1(+) dendritic cells (DCs) have been suggested to sample intestinal antigens by extending transepithelial dendrites into the gut lumen. Other studies identified CD103(+) DCs in the mucosa,which,through their ability to synthesize retinoic acid (RA),appear to be capable of generating typical signatures of intestinal adaptive immune responses. We report that CD103 and CX3CR1 phenotypically and functionally characterize distinct subsets of lamina propria cells. In contrast to CD103(+) DC,CX3CR1(+) cells represent a nonmigratory gut-resident population with slow turnover rates and poor responses to FLT-3L and granulocyte/macrophage colony-stimulating factor. Direct visualization of cells in lymph vessels and flow cytometry of mouse intestinal lymph revealed that CD103(+) DCs,but not CX3CR1-expressing cells,migrate into the gut draining mesenteric lymph nodes (LNs) under steady-state and inflammatory conditions. Moreover,CX3CR1(+) cells displayed poor T cell stimulatory capacity in vitro and in vivo after direct injection of cells into intestinal lymphatics and appeared to be less efficient at generating RA compared with CD103(+) DC. These findings indicate that selectively CD103(+) DCs serve classical DC functions and initiate adaptive immune responses in local LNs,whereas CX3CR1(+) populations might modulate immune responses directly in the mucosa and serve as first line barrier against invading enteropathogens. View Publication

The ability of NK cells to directly recognize pathogens and be activated via Toll-like receptors (TLR) is increasingly recognized. Nevertheless,controversial results on the NK cell ability to be directly activated by lipopolysaccharide (LPS),the ligand of TLR4,have been recently reported. To start elucidating the reasons explaining the contrasting observations of the literature,we focused on the potential role of currently used NK cell purification procedures to condition putative NK cell responsiveness to LPS. To do so,human NK cells were isolated by negative selection,using three different commercial kits,to be comparatively evaluated for the production of IFNgamma in response to ultra-pure LPS and/or IL-2. Despite the lack of surface TLR4,we found that two out of the three NK cell-enriched populations released IFNgamma (and one of the two,IL-12p70 as well) in response to the LPS plus IL-2 combination,whereas the last one did not. However,the two LPS plus IL-2-responsive NK cell populations were found variably contaminated with 6-sulfo LacNAc(+) dendritic cells (slanDC),demonstrated responsible for triggering,via the production of IL-12p70 in response to LPS,the release of IFNgamma by IL-2-stimulated NK cells. Accordingly,slanDC depletion completely abrogated the capacity to produce both IL-12p70 and IFNgamma in response to LPS plus IL-2 by slanDC-containing NK cells. Taken together,our data uncover that two commercially available kits,specifically designed to isolate NK cells by negative selection,also co-purify variable amounts of slanDC. The latter cells may dramatically affect the outcome of experiments carried on to evaluate NK cell responsiveness to TLR agonists such as LPS. View Publication

Although natural Abs (NAbs) are present from birth,little is known about what drives their selection and whether they have housekeeping functions. The prototypic T15-NAb,first identified because of its protective role in infection,is representative of a special type of NAb response that specifically recognizes and forms complexes with apoptotic cells and which promotes cell-corpse engulfment by phagocytes. We now show that this T15-NAb IgM-mediated clearance process is dependent on the recruitment of C1q and mannose-binding lectin,which have known immune modulatory activities that also provide eat me" signals for enhancing phagocytosis. Further investigation revealed that the addition of T15-NAb significantly suppressed in vitro LPS-induced TNF-alpha and IL-6 secretion by the macrophage-like cell line� View Publication

Natural Abs,which arise without known immune exposure,have been described that specifically recognize cells dying from apoptosis,but their role in innate immunity remains poorly understood. Herein,we show that the immune response to neoantigenic determinants on apoptotic thymocytes is dominated by Abs to oxidation-associated Ags,phosphorylcholine (PC),a head group that becomes exposed during programmed cell death,and malondialdehyde (MDA),a reactive aldehyde degradation product of polyunsaturated lipids produced following exposure to reactive oxidation species. While natural Abs to apoptotic cells in naive adult mice were dominated by PC and MDA specificities,the amounts of these Abs were substantially boosted by treatment of mice with apoptotic cells. Moreover,the relative amounts of PC and MDA Abs was affected by V(H) gene inheritance. Ab interactions with apoptotic cells also mediated the recruitment of C1q,which enhanced apoptotic cell phagocytosis by immature dendritic cells. Significantly,IgM Abs to both PC and MDA were primary factors in determining the efficiency of serum-dependent apoptotic cell phagocytosis. Hence,we demonstrate a mechanism by which certain natural Abs that recognize neoantigens on apoptotic cells,in naive mice and those induced by immune exposure to apoptotic cells,can enhance the functional capabilities of immature dendritic cells for phagocytic engulfment of apoptotic cells. 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