技术资料

T cell activation in response to Ag is largely regulated by protein posttranslational modifications. Although phosphorylation has been extensively characterized in T cells,much less is known about the glycosylation of serine/threonine residues by O-linked N-acetylglucosamine (O-GlcNAc). Given that O-GlcNAc appears to regulate cell signaling pathways and protein activity similarly to phosphorylation,we performed a comprehensive analysis of O-GlcNAc during T cell activation to address the functional importance of this modification and to identify the modified proteins. Activation of T cells through the TCR resulted in a global elevation of O-GlcNAc levels and in the absence of O-GlcNAc,IL-2 production and proliferation were compromised. T cell activation also led to changes in the relative expression of O-GlcNAc transferase (OGT) isoforms and accumulation of OGT at the immunological synapse of murine T cells. Using a glycoproteomics approach,we identified textgreater200 O-GlcNAc proteins in human T cells. Many of the identified proteins had a functional relationship to RNA metabolism,and consistent with a connection between O-GlcNAc and RNA,inhibition of OGT impaired nascent RNA synthesis upon T cell activation. Overall,our studies provide a global analysis of O-GlcNAc dynamics during T cell activation and the first characterization,to our knowledge,of the O-GlcNAc glycoproteome in human T cells. View Publication

Leukocyte microvilli are flexible projections enriched with adhesion molecules. The role of these cellular projections in the ability of T cells to probe antigen-presenting cells has been elusive. In this study,we probe the spatial relation of microvilli and T-cell receptors (TCRs),the major molecules responsible for antigen recognition on the T-cell membrane. To this end,an effective and robust methodology for mapping membrane protein distribution in relation to the 3D surface structure of cells is introduced,based on two complementary superresolution microscopies. Strikingly,TCRs are found to be highly localized on microvilli,in both peripheral blood human T cells and differentiated effector T cells,and are barely found on the cell body. This is a decisive demonstration that different types of T cells universally localize their TCRs to microvilli,immediately pointing to these surface projections as effective sensors for antigenic moieties. This finding also suggests how previously reported membrane clusters might form,with microvilli serving as anchors for specific T-cell surface molecules. View Publication

Binding of ICAM-1 (intercellular adhesion molecule-1) to the β2-integrin LFA-1 (leukocyte function associated antigen-1) is known to induce crosstalk to the α4β1 integrin. Using different LFA-1 monoclonal antibodies we have been able to study the requirement and mechanism of action for the crosstalk in considerable detail. LFA-1 activating antibodies and those inhibitory antibodies that signal to α4β1 induce phosphorylation of Thr-758 on the β2-chain,which is followed by binding of 14-3-3 proteins and signaling through the G protein exchange factor Tiam1. This results in dephosphorylation of Thr-788/789 on the β1-chain of α4β1 and loss of binding to its ligand VCAM-1 (vascular cell adhesion molecule-1). The results show that with LFA-1 antibodies,we can either 1) activate LFA-1 and inhibit α4β1,2) inhibit both LFA-1 and α4β1,3) inhibit LFA-1 but not α4β1 or 4) not affect LFA-1 or α4β1 These findings are important for the understanding of integrin regulation and for the interpretation of the effect of integrin antibodies and their use in clinical applications. View Publication

Group 2 innate lymphoid cells (ILC2s) in the lung are stimulated by inhaled allergens. ILC2s do not directly recognize allergens but they are stimulated by cytokines including interleukin (IL)-33 released by damaged epithelium. In response to allergens,lung ILC2s produce T helper 2 cell type cytokines inducing T cell-independent allergic lung inflammation. Here we examined the fate of lung ILC2s upon allergen challenges. ILC2s proliferated and secreted cytokines upon initial stimulation with allergen or IL-33,and this phase was followed by a contraction phase as cytokine production ceased. Some ILC2s persisted long after the resolution of the inflammation as allergen-experienced ILC2s and responded to unrelated allergens more potently than naive ILC2s,mediating severe allergic inflammation. The allergen-experienced ILC2s exhibited a gene expression profile similar to that of memory T cells. The memory-like properties of allergen-experienced ILC2s may explain why asthma patients are often sensitized to multiple allergens. View Publication

Haplo-cord stem cell transplantation combines the infusion of CD34 selected hematopoietic progenitors from a haplo-identical donor with an umbilical cord blood (UCB) graft from an unrelated donor and allows faster count recovery,with low rates of disease recurrence and chronic graft-versus-host disease (GVHD). But the contribution of the umbilical cord blood graft to long-term transplant outcome remains unclear. We analyzed 39 recipients of haplo-cord transplants with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS),engrafted and in remission at 2 months. Median age was 66 (18-72) and all had intermediate,high,or very-high risk disease. Less than 20% UCB chimerism in the CD33 lineage was associated with an increased rate of disease recurrence (54% versus 11% p textless 0.0001) and decrease in one year progression-free (20% versus 55%,p = 0.004) and overall survival (30% versus 62%,p = 0.02). Less than 100% UCB chimerism in the CD3 lineage was associated with increase rate of disease recurrence (46% versus 12%,p = 0.007). Persistent haplo-chimerism in the CD3 lineage was associated with an increased rate of disease recurrence (40% versus 15%,p = 0.009) Chimerism did not predict for treatment related mortality. The cumulative incidence of acute GVHD by day 100 was 43%. The cumulative incidence of moderate/severe chronic GVHD was only 5%. Engraftment of the umbilical cord blood grafts provides powerful graft-versus-leukemia (GVL) effects which protect against disease recurrence and is associated with low risk of chronic GVHD. Engraftment of CD34 selected haplo-identical cells can lead to rapid development of circulating T-cells,but when these cells dominate,GVL-effects are limited and rates of disease recurrence are high. View Publication

Small molecules are powerful tools for investigating protein function and can serve as leads for new therapeutics. Most human proteins,however,lack small-molecule ligands,and entire protein classes are considered 'undruggable'. Fragment-based ligand discovery can identify small-molecule probes for proteins that have proven difficult to target using high-throughput screening of complex compound libraries. Although reversibly binding ligands are commonly pursued,covalent fragments provide an alternative route to small-molecule probes,including those that can access regions of proteins that are difficult to target through binding affinity alone. Here we report a quantitative analysis of cysteine-reactive small-molecule fragments screened against thousands of proteins in human proteomes and cells. Covalent ligands were identified for textgreater700 cysteines found in both druggable proteins and proteins deficient in chemical probes,including transcription factors,adaptor/scaffolding proteins,and uncharacterized proteins. Among the atypical ligand-protein interactions discovered were compounds that react preferentially with pro- (inactive) caspases. We used these ligands to distinguish extrinsic apoptosis pathways in human cell lines versus primary human T cells,showing that the former is largely mediated by caspase-8 while the latter depends on both caspase-8 and -10. Fragment-based covalent ligand discovery provides a greatly expanded portrait of the ligandable proteome and furnishes compounds that can illuminate protein functions in native biological systems. View Publication

The persistence of latent HIV proviruses in long-lived CD4(+) T cells despite antiretroviral therapy (ART) is a major obstacle to viral eradication. Because current candidate latency-reversing agents (LRAs) induce HIV transcription,but fail to clear these cellular reservoirs,new approaches for killing these reactivated latent HIV reservoir cells are urgently needed. HIV latency depends upon the transcriptional quiescence of the integrated provirus and the circumvention of immune defense mechanisms. These defenses include cell-intrinsic innate responses that use pattern-recognition receptors (PRRs) to detect viral pathogens,and that subsequently induce apoptosis of the infected cell. Retinoic acid (RA)-inducible gene I (RIG-I,encoded by DDX58) forms one class of PRRs that mediates apoptosis and the elimination of infected cells after recognition of viral RNA. Here we show that acitretin,an RA derivative approved by the US Food and Drug Administration (FDA),enhances RIG-I signaling ex vivo,increases HIV transcription,and induces preferential apoptosis of HIV-infected cells. These effects are abrogated by DDX58 knockdown. Acitretin also decreases proviral DNA levels in CD4(+) T cells from HIV-positive subjects on suppressive ART,an effect that is amplified when combined with suberoylanilide hydroxamic acid (SAHA),a histone deacetylase inhibitor. Pharmacological enhancement of an innate cellular-defense network could provide a means by which to eliminate reactivated cells in the latent HIV reservoir. View Publication

Chronic viruses and cancers thwart immune responses in humans by inducing T cell dysfunction. Using a murine chronic virus that models human infections,we investigated the function of the adhesion molecule,P-selectin glycoprotein ligand-1 (PSGL-1),that is upregulated on responding T cells. PSGL-1-deficient mice cleared the virus due to increased intrinsic survival of multifunctional effector T cells that had downregulated PD-1 as well as other inhibitory receptors. Notably,this response resulted in CD4(+)-T-cell-dependent immunopathology. Mechanistically,PSGL-1 ligation on exhausted CD8(+) T cells inhibited T cell receptor (TCR) and interleukin-2 (IL-2) signaling and upregulated PD-1,leading to diminished survival with TCR stimulation. In models of melanoma cancer in which T cell dysfunction occurs,PSGL-1 deficiency led to PD-1 downregulation,improved T cell responses,and tumor control. Thus,PSGL-1 plays a fundamental role in balancing viral control and immunopathology and also functions to regulate T cell responses in the tumor microenvironment. View Publication

Regulatory T (Treg) cells expressing Foxp3 transcripton factor are essential for immune homeostasis. They arise in the thymus as a separate lineage from conventional CD4(+)Foxp3(-) T (Tconv) cells. Here,we show that the thymic development of Treg cells depends on the expression of their endogenous cognate self-antigen. The formation of these cells was impaired in mice lacking this self-antigen,while Tconv cell development was not negatively affected. Thymus-derived Treg cells were selected by self-antigens in a specific manner,while autoreactive Tconv cells were produced through degenerate recognition of distinct antigens. These distinct modes of development were associated with the expression of T cell receptor of higher functional avidity for self-antigen by Treg cells than Tconv cells,a difference subsequently essential for the control of autoimmunity. Our study documents how self-antigens define the repertoire of thymus-derived Treg cells to subsequently endow this cell type with the capacity to undermine autoimmune attack. View Publication

Class I HLA molecules mark infected cells for immune targeting by presenting pathogen-encoded peptides on the cell surface. Characterization of viral peptides unique to infected cells is important for understanding CD8(+) T cell responses and for the development of T cell-based immunotherapies. Having previously reported a series of West Nile virus (WNV) epitopes that are naturally presented by HLA-A*02:01,in this study we generated TCR mimic (TCRm) mAbs to three of these peptide/HLA complexes-the immunodominant SVG9 (E protein),the subdominant SLF9 (NS4B protein),and the immunorecessive YTM9 (NS3 protein)-and used these TCRm mAbs to stain WNV-infected cell lines and primary APCs. TCRm staining of WNV-infected cells demonstrated that the immunorecessive YTM9 appeared several hours earlier and at 5- to 10-fold greater density than the more immunogenic SLF9 and SVG9 ligands,respectively. Moreover,staining following inhibition of the TAP demonstrated that all three viral ligands were presented in a TAP-dependent manner despite originating from different cellular compartments. To our knowledge,this study represents the first use of TCRm mAbs to define the kinetics and magnitude of HLA presentation for a series of epitopes encoded by one virus,and the results depict a pattern whereby individual epitopes differ considerably in abundance and availability. The observations that immunodominant ligands can be found at lower levels and at later time points after infection suggest that a reevaluation of the factors that combine to shape T cell reactivity may be warranted. View Publication

Many pathogens evade cytotoxic T lymphocytes (CTLs) by downregulating HLA molecules on infected cells,but the loss of HLA can trigger NK cell-mediated lysis. HIV-1 is thought to subvert CTLs while preserving NK cell inhibition by Nef-mediated downregulation of HLA-A and -B but not HLA-C molecules. We find that HLA-C is downregulated by most primary HIV-1 clones,including transmitted founder viruses,in contrast to the laboratory-adapted NL4-3 virus. HLA-C reduction is mediated by viral Vpu and reduces the ability of HLA-C restricted CTLs to suppress viral replication in CD4+ cells in vitro. HLA-A/B are unaffected by Vpu,and primary HIV-1 clones vary in their ability to downregulate HLA-C,possibly in response to whether CTLs or NK cells dominate immune pressure through HLA-C. HIV-2 also suppresses HLA-C expression through distinct mechanisms,underscoring the immune pressure HLA-C exerts on HIV. This viral immune evasion casts new light on the roles of CTLs and NK cells in immune responses against HIV. View Publication

T cell development requires a period of postthymic maturation. Why this is the case has remained a mystery,particularly given the rigors of intrathymic developmental checkpoints,successfully traversed by only ∼5% of thymocytes. We now show that the first few weeks of T cell residence in the lymphoid periphery define a period of heightened susceptibility to tolerance induction to tissue-restricted antigens (TRAs),the outcome of which depends on the context in which recent thymic emigrants (RTEs) encounter antigen. After encounter with TRAs in the absence of inflammation,RTEs exhibited defects in proliferation,diminished cytokine production,elevated expression of anergy-associated genes,and diminished diabetogenicity. These properties were mirrored in vitro by enhanced RTE susceptibility to regulatory T cell-mediated suppression. In the presence of inflammation,RTEs and mature T cells were,in contrast,equally capable of inducing diabetes,proliferating,and producing cytokines. Thus,recirculating RTEs encounter TRAs during a transitional developmental stage that facilitates tolerance induction,but inflammation converts antigen-exposed,tolerance-prone RTEs into competent effector cells. View Publication