技术资料

The AP-1 factor basic leucine zipper transcription factor,ATF-like (BATF) is important for CD4(+) Th17,Th9,and follicular Th cell development. However,its precise role in Th2 differentiation and function remains unclear,and the requirement for BATF in nonallergic settings of type-2 immunity has not been explored. In this article,we show that,in response to parasitic helminths,Batf(-/-) mice are unable to generate follicular Th and Th2 cells. As a consequence,they fail to establish productive type-2 immunity during primary and secondary infection. Batf(-/-) CD4(+) T cells do not achieve type-2 cytokine competency,which implies that BATF plays a key role in the regulation of IL-4 and IL-13. In contrast to Th17 and Th9 cell subsets in which BATF binds directly to promoter and enhancer regions to regulate cytokine expression,our results show that BATF is significantly enriched at Rad50 hypersensitivity site (RHS)6 and RHS7 of the locus control region relative to AP-1 sites surrounding type-2 cytokine loci in Th2 cells. Indeed,Batf(-/-) CD4(+) T cells do not obtain permissive epigenetic modifications within the Th2 locus,which were linked to RHS6 and RHS7 function. In sum,these findings reveal BATF as a central modulator of peripheral and humoral hallmarks of type-2 immunity and begin to elucidate a novel mechanism by which it regulates type-2 cytokine production through its modification of the Th2 locus control region. View Publication

Peripheral CD4(+)Vβ5(+) T cells are tolerized to an endogenous mouse mammary tumor virus superantigen either by deletion or TCR revision. Through TCR revision,RAG reexpression mediates extrathymic TCRβ rearrangement and results in a population of postrevision CD4(+)Vβ5(-) T cells expressing revised TCRβ chains. We have hypothesized that cell death pathways regulate the selection of cells undergoing TCR revision to ensure the safety and utility of the postrevision population. In this study,we investigate the role of Bcl-2-interacting mediator of cell death (Bim)-mediated cell death in autoantigen-driven deletion and TCR revision. Bim deficiency and Bcl-2 overexpression in Vβ5 transgenic (Tg) mice both impair peripheral deletion. Vβ5 Tg Bim-deficient and Bcl-2 Tg mice exhibit an elevated frequency of CD4(+) T cells expressing both the transgene-encoded Vβ5 chain and a revised TCRβ chain. We now show that these dual-TCR-expressing cells are TCR revision intermediates and that the population of RAG-expressing,revising CD4(+) T cells is increased in Bim-deficient Vβ5 Tg mice. These findings support a role for Bim and Bcl-2 in regulating the balance of survival versus apoptosis in peripheral T cells undergoing RAG-dependent TCR rearrangements during TCR revision,thereby ensuring the utility of the postrevision repertoire. View Publication

Among different cancer immunotherapy approaches,bispecific antibodies (BsAbs) are of great interest due to their ability to recruit immune cells to kill tumor cells directly. Various BsAbs against Her2 tumor cells have been proposed with potent cytotoxic activities. However,most of these formats require extensive processing to obtain heterodimeric bispecific antibodies. In this study,we describe a bispecific antibody,BiHC (bispecific Her2-CD3 antibody),constructed with a single-domain anti-Her2 and a single-chain Fv (variable fragment) of anti-CD3 in an IgG-like format. In contrast to most IgG-like BsAbs,the two arms in BiHC have different molecular weights,making it easier to separate hetero- or homodimers. BiHC can be expressed in Escherichia coli and purified via Protein A affinity chromatography. The purified BiHC can recruit T cells and induce specific cytotoxicity of Her2-expressing tumor cells in vitro. The BiHC can also efficiently inhibit the tumor growth in vivo. Thus,BiHC is a promising candidate for the treatment of Her2-positive cancers. View Publication

Increasing amounts of pathogen replication usually lead to a proportionate increase in size and effector differentiation of the CD8(+) T cell response,which is attributed to increased Ag and inflammation. Using a murine CMV that is highly sensitive to the antiviral drug famciclovir to modulate virus replication,we found that increased virus replication drove increased effector CD8(+) T cell differentiation,as expected. Paradoxically,however,increased virus replication dramatically decreased the size of the CD8(+) T cell response to two immunodominant epitopes. The decreased response was due to type I IFN-dependent depletion of conventional dendritic cells and could be reproduced by specific depletion of dendritic cells from day 2 postinfection or by sterile induction of type I IFN. Increased virus replication and type I IFN specifically inhibited the response to two immunodominant epitopes that are known to be dependent on Ag cross-presented by DCs,but they did not inhibit the response to inflationary" epitopes whose responses can be sustained by infected nonhematopoietic cells. Our results show that type I IFN can suppress CD8(+) T cell responses to cross-presented Ag by depleting cross-presenting conventional dendritic cells." View Publication

T lymphocytes develop in the thymus from hemopoietic precursors that commit to the T cell lineage under the influence of Notch signals. In this study,we show by single cell analyses that the most immature hemopoietic precursors in the adult mouse thymus are uncommitted and specify to the T cell lineage only after their arrival in the thymus. These precursors express high levels of surface Notch receptors and rapidly lose B cell potential upon the provision of Notch signals. Using a novel culture system with complexed,soluble Notch ligands that allows the titration of T cell lineage commitment,we find that these precursors are highly sensitive to both Delta and Jagged ligands. In contrast,their phenotypical and functional counterparts in the bone marrow are resistant to Notch signals that efficiently induce T cell lineage commitment in thymic precursors. Mechanistically,this is not due to differences in receptor expression,because early T lineage precursors,bone marrow lineage marker-negative,Sca-1-positive,c-Kit-positive and common lymphoid progenitor cells,express comparable amounts of surface Notch receptors. Our data demonstrate that the sensitivity to Notch-mediated T lineage commitment is stage-dependent and argue against the bone marrow as the site of T cell lineage commitment. View Publication

Brucella is a facultative intracellular pathogen and the etiological agent of brucellosis. In some cases,human brucellosis results in a persistent infection that may reactivate years after the initial exposure. The mechanisms by which the parasite evades clearance by the immune response to chronically infect its host are unknown. We recently demonstrated that dendritic cells (DCs),which are critical components of adaptive immunity,are highly susceptible to Brucella infection and are a preferential niche for the development of the bacteria. Here,we report that in contrast to several intracellular bacteria,Brucella prevented the infected DCs from engaging in their maturation process and impaired their capacities to present antigen to naïve T cells and to secrete interleukin-12. Moreover,Brucella-infected DCs failed to release tumor necrosis factor alpha (TNF-alpha),a defect involving the bacterial protein Omp25. Exogenous TNF-alpha addition to Brucella-infected DCs restored cell maturation and allowed them to present antigens. Two avirulent mutants of B. suis,B. suis bvrR and B. suis omp25 mutants,which do not express the Omp25 protein,triggered TNF-alpha production upon DC invasion. Cells infected with these mutants subsequently matured and acquired the ability to present antigens,two properties which were dramatically impaired by addition of anti-TNF-alpha antibodies. In light of these data,we propose a model in which virulent Brucella alters the maturation and functions of DCs through Omp25-dependent control of TNF-alpha production. This model defines a specific evasion strategy of the bacteria by which they can escape the immune response to chronically infect their host. View Publication

Regions of the normal arterial intima predisposed to atherosclerosis are sites of ongoing monocyte trafficking and also contain resident myeloid cells with features of dendritic cells. However,the pathophysiological roles of these cells are poorly understood. Here we found that intimal myeloid cells underwent reverse transendothelial migration (RTM) into the arterial circulation after systemic stimulation of pattern-recognition receptors (PRRs). This process was dependent on expression of the chemokine receptor CCR7 and its ligand CCL19 by intimal myeloid cells. In mice infected with the intracellular pathogen Chlamydia muridarum,blood monocytes disseminated infection to the intima. Subsequent CCL19-CCR7-dependent RTM was critical for the clearance of intimal C. muridarum. This process was inhibited by hypercholesterolemia. Thus,RTM protects the normal arterial intima,and compromised RTM during atherogenesis might contribute to the intracellular retention of pathogens in atherosclerotic lesions. View Publication

The T-cell surface molecule TIGIT is an immune checkpoint molecule that inhibits T-cell responses,but its roles in cancer are little understood. In this study,we evaluated the role TIGIT checkpoint plays in the development and progression of gastric cancer. We show that the percentage of CD8 T cells that are TIGIT+ was increased in gastric cancer patients compared with healthy individuals. These cells showed functional exhaustion with impaired activation,proliferation,cytokine production,and metabolism,all of which were rescued by glucose. In addition,gastric cancer tissue and cell lines expressed CD155,which bound TIGIT receptors and inactivated CD8 T cells. In a T cell-gastric cancer cell coculture system,gastric cancer cells deprived CD8 T cells of glucose and impaired CD8 T-cell effector functions; these effects were neutralized by the additional glucose or by TIGIT blockade. In gastric cancer tumor cells,CD155 silencing increased T-cell metabolism and IFNγ production,whereas CD155 overexpression inhibited T-cell metabolism and IFNγ production; this inhibition was neutralized by TIGIT blockade. Targeting CD155/TIGIT enhanced CD8 T-cell reaction and improved survival in tumor-bearing mice. Combined targeting of TIGIT and PD-1 further enhanced CD8 T-cell activation and improved survival in tumor-bearing mice. Our results suggest that gastric cancer cells inhibit CD8 T-cell metabolism through CD155/TIGIT signaling,which inhibits CD8 T-cell effector functions,resulting in hyporesponsive antitumor immunity. These findings support the candidacy of CD155/TIGIT as a potential therapeutic target in gastric cancer. Cancer Res; 77(22); 6375-88. textcopyright2017 AACR. View Publication

Although CD31 expression on human thymocytes has been reported,a detailed analysis of CD31 expression at various stages of T cell development in the human thymus is missing. In this study,we provide a global picture of the evolution of CD31 expression from the CD34(+) hematopoietic precursor to the CD45RA(+) mature CD4(+) and CD8(+) single-positive (SP) T cells. Using nine-color flow cytometry,we show that CD31 is highly expressed on CD34(+) progenitors and stays high until the early double-positive stage (CD3(-)CD4(+)CD8α(+)β(-)). After β-selection,CD31 expression levels become low to undetectable. CD31 expression then increases and peaks on CD3(high)CD4(+)CD8(+) double-positive thymocytes. However,following positive selection,CD31 expression differs dramatically between CD4(+) and CD8(+) lineages: homogeneously high on CD8 SP but lower or negative on CD4 SP cells,including a subset of CD45RA(+)CD31(-) mature CD4(+) thymocytes. CD31 expression on TCRγδ thymocytes is very similar to that of CD4 SP cells. Remarkably,there is a substantial subset of semimature (CD45RA(-)) CD4 SP thymocytes that lack CD31 expression. Moreover,FOXP3(+) and ICOS(+) cells are overrepresented in this CD31(-) subpopulation. Despite this CD31(-)CD45RA(-) subpopulation,most egress-capable mature CD45RA(+) CD4 SP thymocytes express CD31. The variations in CD31 expression appear to coincide with three major selection processes occurring during thymopoiesis: β-selection,positive selection,and negative selection. Considering the ability of CD31 to modulate the TCR's activation threshold via the recruitment of tyrosine phosphatases,our results suggest a significant role for CD31 during T cell development. View Publication

NK cells play an important role in the innate immune response. We have isolated NK cells from human lymphoid tissues and found that these cells express the CD4 molecule on their surface at levels higher than those found on peripheral blood NK cells. To study the functional role of the CD4 molecule on NK cells,we developed an in vitro system by which we are able to obtain robust CD4 expression on NK cells derived from blood. CD4+ NK cells efficiently mediate NK cell cytotoxicity,and CD4 expression does not appear to alter lytic function. CD4+ NK cells are more likely to produce the cytokines gamma-IFN and TNF-alpha than are CD4- NK cells. Ligation of CD4 further increases the number of NK cells producing these cytokines. NK cells expressing CD4 are also capable of migrating toward the CD4-specific chemotactic factor IL-16,providing another function for the CD4 molecule on NK cells. Thus,the CD4 molecule is present and functional on NK cells and plays a role in innate immune responses as a chemotactic receptor and by increasing cytokine production,in addition to its well-described function on T cells as a coreceptor for Ag responsive cell activation. View Publication

Ab-mediated lymphoablation is commonly used in solid organ and hematopoietic cell transplantation. However,these strategies fail to control pathogenic memory T cells efficiently and to improve long-term transplant outcomes significantly. Understanding the mechanisms of T cell reconstitution is critical for enhancing the efficacy of Ab-mediated depletion in sensitized recipients. Using a murine analog of anti-thymocyte globulin (mATG) in a mouse model of cardiac transplantation,we previously showed that peritransplant lymphocyte depletion induces rapid memory T cell proliferation and only modestly prolongs allograft survival. We now report that T cell repertoire following depletion is dominated by memory CD4 T cells. Additional depletion of these residual CD4 T cells severely impairs the recovery of memory CD8 T cells after mATG treatment. The CD4 T cell help during CD8 T cell recovery depends on the presence of B cells expressing CD40 and intact CD40/CD154 interactions. The requirement for CD4 T cell help is not limited to the use of mATG in heart allograft recipients,and it is observed in nontransplanted mice and after CD8 T cell depletion with mAb instead of mATG. Most importantly,limiting helper signals increases the efficacy of mATG in controlling memory T cell expansion and significantly extends heart allograft survival in sensitized recipients. Our findings uncover the novel role for helper memory CD4 T cells during homeostatic CD8 T cell proliferation and open new avenues for optimizing lymphoablative therapies in allosensitized patients. View Publication

Murine CMV (MCMV) establishes a systemic,low-level persistent infection resulting in the accumulation of CD8(+) T cells specific for a subset of viral epitopes,a process called memory inflation. Although replicating virus is rarely detected in chronically infected C57BL/6 mice,these inflationary cells display a phenotype suggestive of repeated Ag stimulation,and they remain functional. CD4(+) T cells have been implicated in maintaining the function and/or number of CD8(+) T cells in other chronic infections. Moreover,CD4(+) T cells are essential for complete control of MCMV. Thus,we wondered whether CD4(+) T cell deficiency would result in impaired MCMV-specific CD8(+) T cell responses. Here we show that CD4(+) T cell deficiency had an epitope-specific impact on CD8(+) T cell memory inflation. Of the three codominant T cell responses during chronic infection,only accumulation of the late-appearing IE3-specific CD8(+) T cells was substantially impaired in CD4(+) T cell-deficient mice. Moreover,the increased viral activity did not drive increased CD8(+) T cell division or substantial dysfunction in any MCMV-specific population that we studied. These data show that CD4(+) T cell help is needed for inflation of a response that develops only during chronic infection but is otherwise dispensable for the steady state maintenance and function of MCMV-specific CD8(+) T cells. View Publication