Showing papers on "Antigen published in 2001"
TL;DR: Regulatory CD4 T cells expressing high levels of the IL-2 receptor are present in humans, providing the opportunity to determine whether alterations of these populations of T cells are involved in the induction of human autoimmune disorders.
Abstract: Thymectomy in mice on neonatal day 3 leads to the development of multiorgan autoimmune disease due to loss of a CD(+)CD25(+) T cell regulatory population in their peripheral lymphoid tissues. Here, we report the identification of a CD4(+) population of regulatory T cells in the circulation of humans expressing high levels of CD25 that exhibit in vitro characteristics identical with those of the CD4(+)CD25(+) regulatory cells isolated in mice. With TCR cross-linking, CD4(+)CD25(high) cells did not proliferate but instead totally inhibited proliferation and cytokine secretion by activated CD4(+)CD25(-) responder T cells in a contact-dependent manner. The CD4(+)CD25(high) regulatory T cells expressed high levels of CD45RO but not CD45RA, akin to the expression of CD45RB(low) on murine CD4(+)CD25(+) regulatory cells. Increasing the strength of signal by providing either costimulation with CD28 cross-linking or the addition of IL-2 to a maximal anti-CD3 stimulus resulted in a modest induction of proliferation and the loss of observable suppression in cocultures of CD4(+)CD25(high) regulatory cells and CD4(+)CD25(-) responder cells. Whereas higher ratios of CD4(+)CD25(high) T cells are required to suppress proliferation if the PD-L1 receptor is blocked, regulatory cell function is shown to persist in the absence of the PD-1/PD-L1 or CTLA-4/B7 pathway. Thus, regulatory CD4 T cells expressing high levels of the IL-2 receptor are present in humans, providing the opportunity to determine whether alterations of these populations of T cells are involved in the induction of human autoimmune disorders.
1,849 citations
TL;DR: Almost all of the key molecules involved in the innate and adaptive immune response are glycoproteins, and specific glycoforms are involved in recognition events.
Abstract: Almost all of the key molecules involved in the innate and adaptive immune response are glycoproteins. In the cellular immune system, specific glycoforms are involved in the folding, quality control, and assembly of peptide-loaded major histocompatibility complex (MHC) antigens and the T cell receptor complex. Although some glycopeptide antigens are presented by the MHC, the generation of peptide antigens from glycoproteins may require enzymatic removal of sugars before the protein can be cleaved. Oligosaccharides attached to glycoproteins in the junction between T cells and antigen-presenting cells help to orient binding faces, provide protease protection, and restrict nonspecific lateral protein-protein interactions. In the humoral immune system, all of the immunoglobulins and most of the complement components are glycosylated. Although a major function for sugars is to contribute to the stability of the proteins to which they are attached, specific glycoforms are involved in recognition events. For example, in rheumatoid arthritis, an autoimmune disease, agalactosylated glycoforms of aggregated immunoglobulin G may induce association with the mannose-binding lectin and contribute to the pathology.
1,474 citations
TL;DR: It is shown in a human in vitro model system that exosomes, a population of small membrane vesicles secreted by living tumor cells, contain and transfer tumor antigens to dendritic cells, relevant for immunointerventions.
Abstract: The initiation of T-cell-mediated antitumor immune responses requires the uptake and processing of tumor antigens by dendritic cells and their presentation on MHC-I molecules. Here we show in a human in vitro model system that exosomes, a population of small membrane vesicles secreted by living tumor cells, contain and transfer tumor antigens to dendritic cells. After mouse tumor exosome uptake, dendritic cells induce potent CD8+ T-cell-dependent antitumor effects on syngeneic and allogeneic established mouse tumors. Therefore, exosomes represent a novel source of tumor-rejection antigens for T-cell cross priming, relevant for immunointerventions.
1,446 citations
TL;DR: Masking of NK cell recognition of ULBP or MIC antigens by UL16 provides a potential mechanism by which human cytomegalovirus-infected cells might evade attack by the immune system.
1,268 citations
TL;DR: It is shown that IL-10 production by DCs is critical for the induction of tolerance, and that phenotypically mature pulmonary DCs mediate tolerance induced by respiratory exposure to antigen.
Abstract: Respiratory exposure to allergen induces T cell tolerance and protection against the development of airway hyperreactivity and asthma. However, the specific mechanisms by which tolerance is induced by respiratory allergen are not clear. We report here that pulmonary dendritic cells (DCs) from mice exposed to respiratory antigen transiently produced interleukin 10 (IL-10). These phenotypically mature pulmonary DCs, which were B-7hi as well as producing IL-10, stimulated the development of CD4+ T regulatory 1–like cells that also produced high amounts of IL-10. In addition, adoptive transfer of pulmonary DCs from IL-10+/+, but not IL-10−/−, mice exposed to respiratory antigen induced antigen-specific unresponsiveness in recipient mice. These studies show that IL-10 production by DCs is critical for the induction of tolerance, and that phenotypically mature pulmonary DCs mediate tolerance induced by respiratory exposure to antigen.
1,241 citations
TL;DR: The capacity of SLE patients' serum to induce DC differentiation correlated with disease activity and depended on the actions of interferon-α (IFN-α), suggesting unabated induction of DCs by IFN- α may drive the autoimmune response in SLE.
Abstract: Dendritic cells (DCs) are important in regulating both immunity and tolerance. Hence, we hypothesized that systemic lupus erythematosus (SLE), an autoimmune disease characterized by autoreactive B and T cells, may be caused by alterations in the functions of DCs. Consistent with this, monocytes from SLE patients' blood were found to function as antigen-presenting cells, in vitro. Furthermore, serum from SLE patients induced normal monocytes to differentiate into DCs. These DCs could capture antigens from dying cells and present them to CD4-positive T cells. The capacity of SLE patients' serum to induce DC differentiation correlated with disease activity and depended on the actions of interferon-alpha (IFN-alpha). Thus, unabated induction of DCs by IFN-alpha may drive the autoimmune response in SLE.
1,234 citations
TL;DR: Recent findings in TR cell biology are reviewed, a model for how TR cells may inhibit the development of immune pathology is outlined and potential therapeutic benefits that may arise from the manipulation of TR cell function are discussed.
Abstract: It is now well established that regulatory T (T(R)) cells can inhibit harmful immunopathological responses directed against self or foreign antigens. However, many key aspects of T(R) cell biology remain unresolved, especially with regard to their antigen specificities and the cellular and molecular pathways involved in their development and mechanisms of action. We will review here recent findings in these areas, outline a model for how T(R) cells may inhibit the development of immune pathology and discuss potential therapeutic benefits that may arise from the manipulation of T(R) cell function.
1,231 citations
TL;DR: The functional role of astrocytes as immune effector cells and how this may influence aspects of inflammation and immune reactivity within the brain follows, emphasizing the involvement of astracytes in promoting Th2 responses.
Abstract: Astrocytes are the major glial cell within the central nervous system (CNS) and have a number of important physiological properties related to CNS homeostasis. The aspect of astrocyte biology addressed in this review article is the astrocyte as an immunocompetent cell within the brain. The capacity of astrocytes to express class II major histocompatibility complex (MHC) antigens and costimulatory molecules (B7 and CD40) that are critical for antigen presentation and T-cell activation are discussed. The functional role of astrocytes as immune effector cells and how this may influence aspects of inflammation and immune reactivity within the brain follows, emphasizing the involvement of astrocytes in promoting Th2 responses. The ability of astrocytes to produce a wide array of chemokines and cytokines is discussed, with an emphasis on the immunological properties of these mediators. The significance of astrocytic antigen presentation and chemokine/cytokine production to neurological diseases with an immunological component is described.
1,220 citations
TL;DR: The data demonstrate that the CTL response against melanoma antigens is an important component of the therapeutic antitumor response and that the reactivity of these CTLs can be augmented through interference with immunoregulatory mechanisms.
Abstract: Therapeutic efficacy of a tumor cell–based vaccine against experimental B16 melanoma requires the disruption of either of two immunoregulatory mechanisms that control autoreactive T cell responses: the cytotoxic T lymphocyte–associated antigen (CTLA)-4 pathway or the CD25+ regulatory T (Treg) cells. Combination of CTLA-4 blockade and depletion of CD25+ Treg cells results in maximal tumor rejection. Efficacy of the antitumor therapy correlates with the extent of autoimmune skin depigmentation as well as with the frequency of tyrosinase-related protein 2180–188–specific CTLs detected in the periphery. Furthermore, tumor rejection is dependent on the CD8+ T cell subset. Our data demonstrate that the CTL response against melanoma antigens is an important component of the therapeutic antitumor response and that the reactivity of these CTLs can be augmented through interference with immunoregulatory mechanisms. The synergism in the effects of CTLA-4 blockade and depletion of CD25+ Treg cells indicates that CD25+ Treg cells and CTLA-4 signaling represent two alternative pathways for suppression of autoreactive T cell immunity. Simultaneous intervention with both regulatory mechanisms is therefore a promising concept for the induction of therapeutic antitumor immunity.
1,070 citations
TL;DR: Evidence is presented that suggests that multiple mechanisms contribute to CD28/B7-mediated T cell costimulation in disease settings that include expansion of activated pathogenic T cells, differentiation of Th1/Th2 cells, and the migration of T cells into target tissues.
Abstract: Recent advances in the understanding of T cell activation have led to new therapeutic approaches in the treatment of immunological disorders. One attractive target of intervention has been the blockade of T cell costimulatory pathways, which result in more selective effects on only those T cells that have encountered specific antigen. In fact, in some instances, costimulatory pathway antagonists can induce antigen-specific tolerance that prevents the progression of autoimmune diseases and organ graft rejection. In this review, we summarize the current understanding of these complex costimulatory pathways including the individual roles of the CD28, CTLA-4, B7-1 (CD80), and B7-2 (CD86) molecules. We present evidence that suggests that multiple mechanisms contribute to CD28/B7-mediated T cell costimulation in disease settings that include expansion of activated pathogenic T cells, differentiation of Th1/Th2 cells, and the migration of T cells into target tissues. Additionally, the negative regulatory role of CTLA-4 in autoimmune diseases and graft rejection supports a dynamic but complex process of immune regulation that is prominent in the control of self-reactivity. This is most apparent in regulation of the CD4(+)CD25(+)CTLA-4(+) immunoregulatory T cells that control multiple autoimmune diseases. The implications of these complexities and the potential for use of these therapies in clinical immune intervention are discussed.
1,061 citations
TL;DR: It is found that this promiscuous gene expression was a cell-autonomous property of medullary epithelial cells and was maintained during the entire period of thymic T cell output, which may facilitate tolerance induction to self-antigens that would otherwise be temporally or spatially secluded from the immune system.
Abstract: Expression of peripheral antigens in the thymus has been implicated in T cell tolerance and autoimmunity. Here we identified medullary thymic epithelial cells as being a unique cell type that expresses a diverse range of tissue-specific antigens. We found that this promiscuous gene expression was a cell-autonomous property of medullary epithelial cells and was maintained during the entire period of thymic T cell output. It may facilitate tolerance induction to self-antigens that would otherwise be temporally or spatially secluded from the immune system. However, the array of promiscuously expressed self-antigens appeared random rather than selected and was not confined to secluded self-antigens.
TL;DR: A skewed maturation of HIV-specific memory CD8+ T cells during HIV infection is demonstrated through analysis of cell division, which demonstrates a two-step process characterized initially by a phase of proliferation largely restricted to the CCR7+CD8+ cell subsets, followed by aphase of functional maturation encompassing the C CR7-CD8- cell subset.
Abstract: Understanding the lineage differentiation of memory T cells is a central question in immunology. We investigated this issue by analysing the expression of the chemokine receptor CCR7, which defines distinct subsets of naive and memory T lymphocytes with different homing and effector capacities and antiviral immune responses to HIV and cytomegalovirus. Ex vivo analysis of the expression of CD45RA and CCR7 antigens, together with in vitro analysis of the cell-division capacity of different memory CD8+ T-cell populations, identified four subsets of HIV- and CMV-specific CD8+ T lymphocytes, and indicated the following lineage differentiation pattern: CD45RA+ CCR7+ --> CD45RA- CCR7+ --> CD45RA- CCR7- --> CD45RA+ CCR7-. Here we demonstrate through analysis of cell division (predominantly restricted to the CCR7+ CD8+ T-cell subsets) that the differentiation of antigen-specific CD8+ T cells is a two-step process characterized initially by a phase of proliferation largely restricted to the CCR7+ CD8+ cell subsets, followed by a phase of functional maturation encompassing the CCR7- CD8+ cell subsets. The distribution of these populations in HIV- and CMV-specific CD8+ T cells showed that the HIV-specific cell pool was predominantly (70%) composed of pre-terminally differentiated CD45RA- CCR7- cells, whereas the CMV-specific cell pool consisted mainly (50%) of the terminally differentiated CD45RA+ CCR7- cells. These results demonstrate a skewed maturation of HIV-specific memory CD8+ T cells during HIV infection.
TL;DR: Protection was associated with the ability of IVIG administration to induce surface expression of FcgammaRIIB on splenic macrophages, and modulation of inhibitory signaling is a potent therapeutic strategy for attenuating autoantibody-triggered inflammatory diseases.
Abstract: The molecular basis for the anti-inflammatory property of intravenous gamma globulin (IVIG) was investigated in a murine model of immune thrombocytopenia. Administration of clinically protective doses of intact antibody or monomeric Fc fragments to wild-type or Fcgamma receptor-humanized mice prevented platelet consumption triggered by a pathogenic autoantibody. The inhibitory Fc receptor, FcgammaRIIB, was required for protection, because disruption either by genetic deletion or with a blocking monoclonal antibody reversed the therapeutic effect of IVIG. Protection was associated with the ability of IVIG administration to induce surface expression of FcgammaRIIB on splenic macrophages. Modulation of inhibitory signaling is thus a potent therapeutic strategy for attenuating autoantibody-triggered inflammatory diseases.
TL;DR: Results show that antigen recognition in the context of infection generates memory cells that are specialized to proliferate in the secondary lymphoid tissues or to fight infection at the site of microbial entry.
Abstract: It is thought that immunity depends on naive CD4 T cells that proliferate in response to microbial antigens, differentiate into memory cells that produce anti-microbial lymphokines, and migrate to sites of infection. Here we use immunohistology to enumerate individual naive CD4 T cells, specific for a model antigen, in the whole bodies of adult mice. The cells resided exclusively in secondary lymphoid tissues, such as the spleen and lymph nodes, in mice that were not exposed to antigen. After injection of antigen alone into the blood, the T cells proliferated, migrated to the lungs, liver, gut and salivary glands, and then disappeared from these organs. If antigen was injected with the microbial product lipopolysaccharide, proliferation and migration were enhanced, and two populations of memory cells survived for months: one in the lymph nodes that produced the growth factor interleukin-2, and a larger one in the non-lymphoid tissues that produced the anti-microbial lymphokine interferon-gamma. These results show that antigen recognition in the context of infection generates memory cells that are specialized to proliferate in the secondary lymphoid tissues or to fight infection at the site of microbial entry.
TL;DR: The contribution of noncytolytic mechanisms to the control of viral infections with a particular emphasis on the role of cytokines is described, by modulating the induction, amplification, recruitment, and effector functions of the immune response.
Abstract: This review describes the contribution of noncytolytic mechanisms to the control of viral infections with a particular emphasis on the role of cytokines in these processes. It has long been known that most cell types in the body respond to an incoming viral infection by rapidly secreting antiviral cytokines such as interferon alpha/beta (IFN-alpha/beta). After binding to specific receptors on the surface of infected cells, IFN-alpha/beta has the potential to trigger the activation of multiple noncytolytic intracellular antiviral pathways that can target many steps in the viral life cycle, thereby limiting the amplification and spread of the virus and attenuating the infection. Clearance of established viral infections, however, requires additional functions of the immune response. The accepted dogma is that complete clearance of intracellular viruses by the immune response depends on the destruction of infected cells by the effector cells of the innate and adaptive immune system [natural killer (NK) cells and cytotoxic T cells (CTLs)]. This notion, however, has been recently challenged by experimental evidence showing that much of the antiviral potential of these cells reflects their ability to produce antiviral cytokines such as IFN-gamma and tumor necrosis factor (TNF)-alpha at the site of the infection. Indeed, these cytokines can purge viruses from infected cells noncytopathically as long as the cell is able to activate antiviral mechanisms and the virus is sensitive to them. Importantly, the same cytokines also control viral infections indirectly, by modulating the induction, amplification, recruitment, and effector functions of the immune response and by upregulating antigen processing and display of viral epitopes at the surface of infected cells. In keeping with these concepts, it is not surprising that a number of viruses encode proteins that have the potential to inhibit the antiviral activity of cytokines.
TL;DR: Splenic MZ and B1 B cells endowed with a "natural memory" provide a bridge between the very early innate and the later appearing adaptive immune response.
TL;DR: Protein microarrays can provide a practical means to characterize patterns of variation in hundreds of thousands of different proteins in clinical or research applications, and are suggested to be sufficient for measurement of many clinically important proteins in patient blood samples.
Abstract: We describe a method for printing protein microarrays, and using these microarrays in a comparative fluorescence assay to measure the abundance of many specific proteins in complex solutions. A robotic device was used to print hundreds of specific antibody or antigen solutions in an array on the surface of derivatized microscope slides. Two complex protein samples, one serving as a standard for comparative quantitation, and the other representing an experimental sample in which the concentrations of specific proteins were to be measured, were labeled by covalent attachment of spectrally-resolvable fluorescent dyes. Specific antibody-antigen interactions localized specific components of the complex mixtures to defined cognate spots in the array, where the relative intensity of the fluorescent signals representing the experimental sample and the reference standard provided a measure of each protein's abundance in the experimental sample. To characterize the specificity, sensitivity and accuracy of this assay, we analyzed the performance of 115 antibody/antigen pairs. 50% of the arrayed antigens, and 20% of the arrayed antibodies, provided specific and accurate measurements of their cognate ligands at or below concentrations of 1.6 µg/ml and 0.34 µg/ml, respectively. Some of the antibody/antigen pairs allowed detection of the cognate ligands at absolute concentrations below 1 ng/ml, and partial concentrations of less than 1 part in 106, sensitivities sufficient for measurement of many clinically important proteins in patient blood samples. Protein microarrays can provide a simple and practical means to characterize patterns of variation in hundreds or thousands of different proteins, in clinical or research applications.
TL;DR: Th3 CD4+ regulatory cells were identified during the course of investigating mechanisms associated with oral tolerance, which may be preferentially generated following oral antigen administration due to the gut immunologic milieu that is rich in TGF‐β and has a unique class of dendritic cells.
Abstract: Th3 CD4+ regulatory cells were identified during the course of investigating mechanisms associated with oral tolerance. Different mechanisms of tolerance are induced following oral antigen administration, including active suppression, clonal anergy and deletion. Low doses favor active suppression whereas high doses favor anergy/deletion. Th3 regulatory cells form a unique T-cell subset which primarily secretes transforming growth factor (TGF)-beta, provides help for IgA and has suppressive properties for both Th1 and Th2 cells. Th3 type cells are distinct from the Th2 cells, as CD4+ TGF-beta-secreting cells with suppressive properties have been generated from interleukin (IL)-4-deficient animals. In vitro differentiation of Th3 cells from Th precursors from T-cell antigen receptor (TCR) transgenic mice is enhanced by culture with TGF-beta, IL-4, IL-10, and anti-IL-12. Th3 CD4+ myelin basic protein regulatory clones are structurally identical to Th1 encephalitogenic clones in TCR usage, MHC restriction and epitope recognition, but produce TGF-beta with various amounts of IL-4 and IL-10. Because Th3 regulatory cells are triggered in an antigen-specific fashion but suppress in an antigen-non-specific fashion, they mediate "bystander suppression" when they encounter the fed autoantigen at the target organ. In vivo induction of Th3 cells and low dose oral tolerance is enhanced by oral administration of IL-4. Anti-CD86 but not anti-CD80 blocks the induction of Th3 cells associated with low dose oral tolerance. Th3 regulatory cells have been described in other systems (e.g. recovery from experimental allergic encephalomyelitis) but may be preferentially generated following oral antigen administration due to the gut immunologic milieu that is rich in TGF-beta and has a unique class of dendritic cells. CD4+CD25+ regulatory T-cell function also appears related to TGF-beta.
TL;DR: Complete list of abbreviations of tumor antigens 707-AP 707 alanine proline-AFP alpha (α)-fetoprotein-ART-4 adenocarcinoma antigen recognized by T cells 4 BAGE B antigen-β-catenin/m β-catensin/mutated-Bcr-abl breakpoint cluster region-Abelson.
Abstract: Complete list of abbreviations of tumor antigens 707-AP 707 alanine proline-AFP alpha (α)-fetoprotein-ART-4 adenocarcinoma antigen recognized by T cells 4 BAGE B antigen-β-catenin/m β-catenin/mutated-Bcr-abl breakpoint cluster region-Abelson - CAMEL CTL-recognized antigen on melanoma CAP-1 carcinoembryonic antigen peptide-1-CASP-8 caspase-8 CDC27m cell-division-cycle 27 mutated-CDK4/m cycline-dependent kinase 4 mutated-CEA carcino-embryonic antigen-CT cancer/testis (antigen)-Cyp-B cyclophilin B DAM differentiation antigen melanoma (the epitopes of DAM-6 and DAM-10 are equivalent, but the gene sequences are different; DAM-6 is also called MAGE-B2. and DAM-10 is also called MAGE-B1) ELF2M elongation factor 2 mutated ETV6-AML1 Ets variant gene 6/acute myeloid leukemia 1 gene ETS G250 glycoprotein 250 - GAGE G antigen GnT-V N-acetylglucosaminyltransferase V -Gp100 glycoprotein 100 kDa-HAGE helicose antigen-HER-2/neu human epidermal receptor-2/ neurological - HLA-A * 0201-R1701 arginine (R) to isoleucine (I) exchange at residue 170 of the α-helix of the α2-domain in the HLA-A2 gene HPV-E7 human papilloma virus E7 HSP70-2M heat shock protein 70-2 mutated HST-2 human signet ring tumor-2 hTERT or hTRT human telomerase reverse transcriptase-iCE intestinal carboxyl esterase KIAA0205 name of the gene as it appears in databases-LAGE L antigen LDLR/FUT low-density lipid receptor/GDP-L-fucose: β-D-galactosidase 2-α-L-fucosyltransferase MAGE melanoma antigen MART-1/Melan-A melanoma antigen recognized by T cells-1/melanoma antigen A MC1R melanocortin 1 receptor Myosin/m myosin mutated-MUC1 mucin 1-MUM-1, -2, -3 melanoma ubiquitous mutated 1, 2, 3 NA88-A NA cDNA clone of patient M88-NY-ESO-1 New York-esophagus 1 - P15 protein 15 p190 minor bcr-abl protein of 190 kDa ber-abl Pml/RARα promyelocytic leukaemia/retinoic acid receptor α-PRAME preferentially expressed antigen of melanoma PSA prostate-specific antigen-PSM prostate-specific membrane antigen-RAGE renal antigen RU1 or RU2 renal ubiquitous 1 or 2 SAGE sarcoma antigen SART-1 or SART-3 squamous antigen rejecting tumor 1 or 3-TEL/ AML1 translocation Ets-family leukemia/acute myeloid leukemia 1 TPI/m triosephosphate isomerase mutated TRP-1 tyrosinase related protein 1, or gp75 TRP-2 tyrosinase related protein 2 TRP-2/ INT2 TRP-2/intron 2 WT1 Wilms' tumor gene Abbreviations used ALL acute lymphoblastic leukemia AML acute myeloid leukemia-APL acute promyelocytic leukemia-CML chronic myelogenous leuke mia-CTL cytotoxic T lymphocytes-Ets E-26 transforming specific (family of transcription factors) H/N head and neck-MHC major histocompatibility complex-NSCLC non-small cell lung carcinoma-ORF open reading frame RCC renal cell carcinoma-SCC squamous cell carcinoma-TSTA tumor-specific transplantation antigens.
TL;DR: It is shown that T-cell activation and proliferation are defective in the absence of ICOS, and ICOS-/- mice showed greatly enhanced susceptibility to experimental autoimmune encephalomyelitis, indicating that ICOS has a protective role in inflammatory autoimmune diseases.
Abstract: T-lymphocyte activation and immune function are regulated by co-stimulatory molecules. CD28, a receptor for B7 gene products, has a chief role in initiating T-cell immune responses1,2. CTLA4, which binds B7 with a higher affinity, is induced after T-cell activation and is involved in downregulating T-cell responses3,4. The inducible co-stimulatory molecule (ICOS), a third member of the CD28/CTLA4 family, is expressed on activated T cells5,6. Its ligand B7H/B7RP-1 is expressed on B cells and in non-immune tissues after injection of lipopolysaccharide into animals6,7. To understand the role of ICOS in T-cell activation and function, we generated and analysed ICOS-deficient mice. Here we show that T-cell activation and proliferation are defective in the absence of ICOS. In addition, ICOS-/- T cells fail to produce interleukin-4 when differentiated in vitro or when primed in vivo. ICOS is required for humoral immune responses after immunization with several antigens. ICOS-/- mice showed greatly enhanced susceptibility to experimental autoimmune encephalomyelitis, indicating that ICOS has a protective role in inflammatory autoimmune diseases.
TL;DR: A synthetic glycolipid ligand for CD1d-restricted natural killer T (NKT) cells expressing the semi-invariant T-cell receptor (Vα14+) is preventive against EAE and targeting NKT cells with this ligand may be an attractive means for intervening in human autoimmune diseases such as multiple sclerosis.
Abstract: Experimental autoimmune encephalomyelitis (EAE) is a prototype autoimmune disease mediated by type 1 helper T (TH1) cells and under the control of regulatory cells. Here we report that a synthetic glycolipid ligand for CD1d-restricted natural killer T (NKT) cells expressing the semi-invariant T-cell receptor (Valpha14+) is preventive against EAE. The ligand is an analogue of alpha-galactosylceramide (alpha-GC), a prototype NKT cell ligand, with a truncated sphingosine chain. alpha-GC causes NKT cells to produce both interferon (IFN)-gamma and interleukin (IL)-4 (refs 4, 5). However, this new ligand can induce a predominant production of IL-4 by the NKT cells. A single injection of this glycolipid, but not of alpha-GC, consistently induced TH2 bias of autoimmune T cells by causing NKT cells to produce IL-4, leading to suppression of EAE. The lack of polymorphism of CD1d and cross-reactive response of mouse and human NKT cells to the same ligand indicates that targeting NKT cells with this ligand may be an attractive means for intervening in human autoimmune diseases such as multiple sclerosis.
TL;DR: It is shown that introduction of three genes encoding the SV40 large-T antigen, the telomerase catalytic subunit, and an H-Ras oncoprotein into primary HMECs results in cells that form tumors when transplanted subcutaneously or into the mammary glands of immunocompromised mice.
Abstract: A number of genetic mutations have been identified in human breast cancers, yet the specific combinations of mutations required in concert to form breast carcinoma cells remain unknown. One approach to identifying the genetic and biochemical alterations required for this process involves the transformation of primary human mammary epithelial cells (HMECs) to carcinoma cells through the introduction of specific genes. Here we show that introduction of three genes encoding the SV40 large-T antigen, the telomerase catalytic subunit, and an H-Ras oncoprotein into primary HMECs results in cells that form tumors when transplanted subcutaneously or into the mammary glands of immunocompromised mice. The tumorigenicity of these transformed cells was dependent on the level of ras oncogene expression. Interestingly, transformation of HMECs but not two other human cell types was associated with amplifications of the c-myc oncogene, which occurred during the in vitro growth of the cells. Tumors derived from the transformed HMECs were poorly differentiated carcinomas that infiltrated through adjacent tissue. When these cells were injected subcutaneously, tumors formed in only half of the injections and with an average latency of 7.5 weeks. Mixing the epithelial tumor cells with Matrigel or primary human mammary fibroblasts substantially increased the efficiency of tumor formation and decreased the latency of tumor formation, demonstrating a significant influence of the stromal microenvironment on tumorigenicity. Thus, these observations establish an experimental system for elucidating both the genetic and cell biological requirements for the development of breast cancer.
TL;DR: It is found that naïve CTLs become committed after as little as 2 h of exposure to APCs and that their subsequent division and differentiation can occur without the need for further antigenic stimulation of the daughter cells, whether priming is in vitro or in vivo.
Abstract: In defense of the host, the immune system must often raise an effective cytotoxic T lymphocyte (CTL) response from a small number of clonal precursors. The degree to which activation stimuli regulate the expansion and differentiation of naive CTLs, however, remains unknown. Using an engineered antigen-presenting cell (APC) system that allows control over antigenic stimulation, we studied the signaling duration requirements for priming and clonal expansion of naive CTLs. We found that naive CTLs become committed after as little as 2 h of exposure to APCs and that their subsequent division and differentiation can occur without the need for further antigenic stimulation of the daughter cells, whether priming is in vitro or in vivo. These data show that after a brief interaction with stimulatory APCs, naive CTLs initiate a program for their autonomous clonal expansion and development into functional effectors.
Journal Article•
TL;DR: The overall immunity to MelAgs after DC vaccination is associated with clinical outcome (P = 0.015), and of 17 patients with evaluable disease, 6 of 7 patients with immunity to two or less Mel Ags had progressive disease 10 weeks after study entry, in contrast to tumor progression in only 1 of 10 patients with Immunity to >2 MelAgS.
Abstract: Immunization to multiple defined tumor antigens for specific immune
therapy of human cancer has thus far proven difficult. Eighteen
HLA A*0201+
patients with metastatic melanoma received injections s.c. of
CD34+progenitor-derived autologous dendritic cells (DCs), which included
Langerhans cells. DCs were pulsed with peptides derived from four
melanoma antigens [(MelAgs) MelanA/MART-1, tyrosinase, MAGE-3, and
gp100], as well as influenza matrix peptide (Flu-MP) and keyhole
limpet hemocyanin (KLH) as control antigens. Overall immunological
effects were assessed by comparing response profiles using marginal
likelihood scores. DC injections were well tolerated except for
progressive vitiligo in two patients. DCs induced an immune response to
control antigens (KLH, Flu-MP) in 16 of 18 patients. An enhanced immune
response to one or more MelAgs was seen in these same 16 patients,
including 10 patients who responded to >2 MelAgs. The two patients
failing to respond to both control and tumor antigens experienced rapid
tumor progression. Of 17 patients with evaluable disease, 6 of 7
patients with immunity to two or less MelAgs had progressive disease 10
weeks after study entry, in contrast to tumor progression in only 1 of
10 patients with immunity to >2 MelAgs. Regression of >1 tumor
metastases were observed in seven of these patients. The overall
immunity to MelAgs after DC vaccination is associated with clinical
outcome (P = 0.015).
TL;DR: Activation of T lymphocytes is thought to require at least two signals, one delivered by the T-cell receptor complex after antigen recognition, and one provided on engagement of co-stimulatory receptors, such as CD28.
Abstract: Activation of T lymphocytes is thought to require at least two signals, one delivered by the T-cell receptor complex after antigen recognition, and one provided on engagement of co-stimulatory receptors, such as CD28. Recent studies are providing clues as to the specific signalling roles of co-stimulatory receptors. Furthermore, superimposition of inhibitory signals, such as those delivered by cytotoxic T-lymphocyte antigen 4 (CTLA-4), leads to a complex network of positive and negative co-stimulatory signals, the integration of which modulates immune responses.
TL;DR: Triggering of BDCA-2 should be evaluated as therapeutic strategy for blocking production of interferon alpha/beta in systemic lupus erythematosus patients.
Abstract: Plasmacytoid dendritic cells are present in lymphoid and nonlymphoid tissue and contribute substantially to both innate and adaptive immunity. Recently, we have described several monoclonal antibodies that recognize a plasmacytoid dendritic cell-specific antigen, which we have termed BDCA-2. Molecular cloning of BDCA-2 revealed that BDCA-2 is a novel type II C-type lectin, which shows 50.7% sequence identity at the amino acid level to its putative murine ortholog, the murine dendritic cell–associated C-type lectin 2. Anti–BDCA-2 monoclonal antibodies are rapidly internalized and efficiently presented to T cells, indicating that BDCA-2 could play a role in ligand internalization and presentation. Furthermore, ligation of BDCA-2 potently suppresses induction of interferon α/β production in plasmacytoid dendritic cells, presumably by a mechanism dependent on calcium mobilization and protein-tyrosine phosphorylation by src-family protein-tyrosine kinases. Inasmuch as production of interferon α/β by plasmacytoid dendritic cells is considered to be a major pathophysiological factor in systemic lupus erythematosus, triggering of BDCA-2 should be evaluated as therapeutic strategy for blocking production of interferon α/β in systemic lupus erythematosus patients.
TL;DR: It is demonstrated here that T-cell–specific blockade of TGF-β signaling allows the generation of an immune response capable of eradicating tumors in mice challenged with live tumor cells.
Abstract: Despite the existence of tumor-specific antigens and demonstrated presence of tumor-specific immune cells, the majority of tumors manage to avoid immune-mediated destruction. Various mechanisms have been suggested for tumor evasion from immune response. One such mechanism is thought to be mediated by transforming growth factor-beta (TGF-beta), an immunosuppressive cytokine found at the site of most tumors. We demonstrate here that T-cell-specific blockade of TGF-beta signaling allows the generation of an immune response capable of eradicating tumors in mice challenged with live tumor cells. In addition, we provide mechanisms through which abrogation of TGF-beta signaling leads to the enhancement of anti-tumor immunity. Our data indicate that T-cell-specific blockade of TGF-beta signaling has strong therapeutic potential to shift the balance of the immune response in favor of anti-tumor immunity.
TL;DR: The data argue for a model in which IFN-γ gene regulation involves an autocrine loop, whereby the cytokine regulates a transcription factor that promotes its own production, and substantially alter the current view of T-bet in IFn-γ regulation and promotion of cell-mediated immune responses.
Abstract: Differentiation of naive CD4(+) T cells into IFN-gamma-producing T helper 1 (T(H)1) cells is pivotal for protective immune responses against intracellular pathogens. T-bet, a recently discovered member of the T-box transcription factor family, has been reported to play a critical role in this process, promoting IFN-gamma production. Although terminal T(H)1 differentiation occurs over days, we now show that challenge of mice with a prototypical T(H)1-inducing stimulus, Toxoplasma gondii soluble extract, rapidly induced IFN-gamma and T-bet; T-bet induction was substantially lower in IFN-gamma-deficient mice. Naive T cells expressed little T-bet, but this transcription factor was induced markedly by the combination of IFN-gamma and cognate antigen. Human myeloid antigen-presenting cells showed T-bet induction after IFN-gamma stimulation alone, and this induction was antagonized by IL-4 and granulocyte/macrophage colony-stimulating factor. Although T-bet was induced rapidly and directly by IFN-gamma, it was not induced by IFN-alpha, lipopolysaccharide, or IL-1, indicating that this action of IFN-gamma was specific. Moreover, T-bet induction was dependent on Stat1 but not Stat4. These data argue for a model in which IFN-gamma gene regulation involves an autocrine loop, whereby the cytokine regulates a transcription factor that promotes its own production. These findings substantially alter the current view of T-bet in IFN-gamma regulation and promotion of cell-mediated immune responses.
TL;DR: In vivo genetic evidence is provided that ICOS delivers a co-stimulatory signal that is essential both for efficient interaction between T and B cells and for normal antibody responses to T-cell-dependent antigens.
Abstract: The outcome of T-cell responses after T-cell encounter with specific antigens is modulated by co-stimulatory signals, which are required for both lymphocyte activation and development of adaptive immunity1,2,3. ICOS4,5, an inducible co-stimulator with homology to CD28, is expressed on activated, but not resting T cells, and shows T-cell co-stimulatory function in vitro. ICOS binds specifically to its counter-receptor B7RP-1 (refs 5,6,7), but not to B7-1 or B7-2. Here we provide in vivo genetic evidence that ICOS delivers a co-stimulatory signal that is essential both for efficient interaction between T and B cells and for normal antibody responses to T-cell-dependent antigens. To determine the physiological function of ICOS, we generated and characterized gene-targeted ICOS-deficient mice. In vivo, a lack of ICOS results in severely deficient T-cell-dependent B-cell responses. Germinal centre formation is impaired and immunoglobulin class switching, including production of allergy-mediating IgE, is defective. ICOS-deficient T cells primed in in vivo and restimulated in vitro with specific antigen produce only low levels of interleukin-4, but remain fully competent to produce interferon-γ.
TL;DR: The cellular immune response to the human immunodeficiency virus, mediated by T lymphocytes, seems strong but fails to control the infection completely, and the failure of the latter to function efficiently facilitates the escape of virus from immune control and the collapse of the whole immune system.
Abstract: The cellular immune response to the human immunodeficiency virus, mediated by T lymphocytes, seems strong but fails to control the infection completely. In most virus infections, T cells either eliminate the virus or suppress it indefinitely as a harmless, persisting infection. But the human immunodeficiency virus undermines this control by infecting key immune cells, thereby impairing the response of both the infected CD4+ T cells and the uninfected CD8+ T cells. The failure of the latter to function efficiently facilitates the escape of virus from immune control and the collapse of the whole immune system.