Showing papers on "Cytotoxic T cell published in 1995"

Identification of RANTES, MIP-1α, and MIP-1β as the Major HIV-Suppressive Factors Produced by CD8+ T Cells

Abstract: Evidence suggests that CD8 + T lymphocytes are involved in the control of human immunodeficiency virus (HIV) infection in vivo, either by cytolytic mechanisms or by the release of HIV-suppressive factors (HIV-SF). The chemokines RANTES, MIP-1α, and MIP-1β were identified as the major HIV-SF produced by CD8 + T cells. Two active proteins purified from the culture supernatant of an immortalized CD8 + T cell clone revealed sequence identity with human RANTES and MIP-1α. RANTES, MIP-1α, and MIP-1β were released by both immortalized and primary CD8 + T cells. HIV-SF activity produced by these cells was completely blocked by a combination of neutralizing antibodies against RANTES, MIP-1α, and MIP-1β. Recombinant human RANTES, MIP-1α, and MIP-1β induced a dose-dependent inhibition of different strains of HIV-1, HIV-2, and simian immunodeficiency virus (SIV). These data may have relevance for the prevention and therapy of AIDS.

Lymphoproliferative Disorders with Early Lethality in Mice Deficient in Ctla-4

Abstract: The role of the cell-surface molecule CTLA-4 in the regulation of T cell activation has been controversial. Here, lymph nodes and spleens of CTLA-4-deficient mice accumulated T cell blasts with up-regulated activation markers. These blast cells also infiltrated liver, heart, lung, and pancreas tissue, and amounts of serum immunoglobulin were elevated. The mice invariably became moribund by 3 to 4 weeks of age. Although CTLA-4-deficient T cells proliferated spontaneously and strongly when stimulated through the T cell receptor, they were sensitive to cell death induced by cross-linking of the Fas receptor and by gamma irradiation. Thus, CTLA-4 acts as a negative regulator of T cell activation and is vital for the control of lymphocyte homeostasis.

Interleukin-12: A Proinflammatory Cytokine with Immunoregulatory Functions that Bridge Innate Resistance and Antigen-Specific Adaptive Immunity

Abstract: Interleukin-12 (IL-12) is a heterodimeric cytokine produced mostly by phagocytic cells in response to bacteria, bacterial products, and intracellular parasites, and to some degree by B lymphocytes. IL-12 induces cytokine production, primarily of IFN-gamma, from NK and T cells, acts as a growth factor for activated NK and T cells, enhances the cytotoxic activity of NK cells, and favors cytotoxic T lymphocyte generation. In vivo IL-12 acts primarily at three stages during the innate resistance/adaptive immune response to infection: 1. Early in the infection, IL-12 is produced and induces production from NK and T cells of IFN-gamma, which contributes to phagocytic cell activation and inflammation; 2. IL-12 and IL-12-induced IFN-gamma favor Th1 cell differentiation by priming CD4+ T cells for high IFN-gamma production; and 3. IL-12 contributes to optimal IFN-gamma production and to proliferation of differentiated Th1 cells in response to antigen. The early preference expressed in the immune response depends on the balance between IL-12, which favors Th1 responses, and IL-4, which favors Th2 responses. Thus, IL-12 represents a functional bridge between the early nonspecific innate resistance and the subsequent antigen-specific adaptive immunity.

CD28 and CTLA-4 have opposing effects on the response of T cells to stimulation.

Abstract: The importance of the B7/CD28/CTLA-4 molecules has been established in studies of antigen-presenting cell-derived B7 and its interaction with the T cell costimulatory molecule CD28. CTLA-4, a T cell surface glycoprotein that is related to CD28, can also interact with B7-1 and B7-2. However, less is known about the function of CTLA-4, which is expressed at highest levels after activation. We have generated an antibody to CTLA-4 to investigate the consequences of engagement of this molecule in a carefully defined system using highly purified T cells. We show here that the presence of low levels of B7-2 on freshly explanted T cells can partially inhibit T cell proliferation, and this inhibition is mediated by interactions with CTLA-4. Cross-linking of CTLA-4 together with the TCR and CD28 strongly inhibits proliferation and IL-2 secretion by T cells. Finally, results show that CD28 and CTLA-4 deliver opposing signals that appear to be integrated by the T cell in determining the response to activation. These data strongly suggest that the outcome of T cell antigen receptor stimulation is regulated by CD28 costimulatory signals, as well as inhibitory signals derived from CTLA-4.

Reconstitution of cellular immunity against cytomegalovirus in recipients of allogeneic bone marrow by transfer of T-cell clones from the donor

Abstract: Background Cytomegalovirus (CMV) disease in immunocompromised patients correlates with a deficiency of CD8+ cytotoxic T lymphocytes specific for CMV. We evaluated the safety and immunologic effects of immunotherapy with clones of these lymphocytes in recipients of allogeneic bone marrow transplants. Methods Clones of CD8+ cytotoxic T cells specific for CMV proteins were isolated from the blood of bone marrow donors. Fourteen patients each received four intravenous infusions of these clones from their donors beginning 30 to 40 days after marrow transplantation. The reconstitution of cellular immunity against CMV was monitored before and during the period of infusions and for up to 12 weeks after the final infusion. The rearranged genes encoding the T-cell receptor served as markers in evaluating the persistence of the transferred T cells. Results No toxic effects related to the infusions were observed. Cytotoxic T cells specific for CMV were reconstituted in all patients. In vitro measurements showed that ...

Dendritic cells produce IL-12 and direct the development of Th1 cells from naive CD4+ T cells.

Abstract: Dendritic cells are APCs that are unique in their potency to stimulate proliferation of primary Ag-specific responses in vitro and in vivo. In this study, we demonstrate that dendritic cells can produce IL-12, a dominant cytokine involved in the development of IFN-gamma-producing T cells. This finding resulted from our observations that dendritic cell-induced Th1 development from total CD4+ T cells upon neutralization of endogenous levels of IL-4 was IL-12-dependent. Furthermore, we demonstrate that dendritic cells can induce the development of Th1 cells from Ag-specific naive LECAM-1bright CD4+ T cells obtained from alpha beta-TCR transgenic mice, provided that CD4+ LECAM-1dull T cells, which produce significant levels of IL-4, are not present in the primary cultures. Production of IL-12 by dendritic cells was confirmed by positive immunofluoresence staining with Abs specific for the inducible IL-12 p40 subunit. This suggests that in addition to inducing proliferation and clonal expansion of naive T cells, dendritic cells, by their production of IL-12, play a direct role in the development of IFN-gamma-producing cells that are important for cell-mediated immune responses.

Cellular and humoral immune responses to viral antigens create barriers to lung-directed gene therapy with recombinant adenoviruses.

Abstract: Recombinant adenoviruses are an attractive vehicle for gene therapy to the lung in the treatment of cystic fibrosis (CF). First-generation viruses deleted of E1a and E1b transduce genes into airway epithelial cells in vivo; however, expression of the transgene is transient and associated with substantial inflammatory responses, and gene transfer is significantly reduced following a second administration of the virus. In this study, we have used mice deficient in immunological effector functions in combination with adoptive and passive transfer techniques to define antigen-specific cellular and humoral immune responses that underlie these important limitations. Our studies indicate that major histocompatibility complex class I-restricted CD8+ cytotoxic T lymphocytes are activated in response to newly synthesized antigens, leading to destruction of virus infected cells and loss of transgene expression. Major histocompatibility complex class II-associated presentation of exogenous viral antigens activates CD4+ T-helper (TH) cells of the TH1 subset and, to a lesser extent, of the TH2 subset. CD4+ cell-mediated responses are insufficient in the absence of cytotoxic T cells to completely eliminate transgene containing cells; however, they contribute to the formation of neutralizing antibodies in the airway which block subsequent adenovirus-mediated gene transfer. Definition of immunological barriers to gene therapy of cystic fibrosis should facilitate the design of rational strategies to overcome them.

Apoptosis of T cells mediated by galectin-1

Abstract: Galectin-1, a member of the family of beta-galactoside binding proteins, has growth regulatory and immunomodulatory activities. We report here that galectin-1, expressed by stromal cells in human thymus and lymph nodes, is present at sites of cell death by apoptosis during normal T-cell development and maturation. Galectin-1 induced apoptosis of activated human T cells and human T leukaemia cell lines. Resting T cells also bound galectin-1, but did not undergo apoptosis. Human endothelial cells that expressed galectin-1 induced apoptosis of bound T cells. Galectin-1-induced apoptosis required expression of CD45, and was decreased when N-glycan elongation was blocked by treatment of the cells by swainsonine, whereas inhibition of O-glycan elongation potentiated the apoptotic effect of galectin-1. Induction of apoptosis by an endogenous mammalian lectin represents a new mechanism for regulating the immune response.

Natural and synthetic non-peptide antigens recognized by human γδ T cells

Abstract: T lymphocytes express either alpha beta or gamma delta T-cell receptor heterodimers. Most alpha beta T cells recognize antigenic peptides bound to major histocompatibility complex molecules but the antigen recognition and biological function of gamma delta T cells is unknown. A major human gamma delta T-cell subset expressing V gamma 2 and V delta 2 germline genes, but having diverse junctional sequences, is found in human mycobacterial lesions and responds in vitro to antigens of bacteria and parasites. In addition, certain haematopoietic tumour cells are specifically recognized and lysed by these T cells. V gamma 2V delta 2-bearing T cells were shown to recognize mycobacterial antigens that are protease resistant and phosphatase sensitive. Because of the difficulty in isolating natural antigens from mycobacterial culture filtrates or extracts, we synthesized a series of monoalkyl phosphates, and found that some, particularly monoethyl phosphate, could mimic the activity of mycobacterial antigens in stimulating these gamma delta T cells. Here we report the identification of natural antigens produced by mycobacteria recognized by human V gamma 2V delta 2-bearing T cells as isopentenyl pyrophosphate and related prenyl pyrophosphate derivatives, compounds involved in the synthesis of complex polyisoprenoid compounds in microbial and mammalian cells. Substitution of phosphate for the pyrophosphate moiety, or elimination of the double bond, greatly reduced antigenic activity of these compounds. These results provide formal evidence that, in contrast to recognition of major histocompatibility complex-bound peptide antigens by alpha beta T cells, human gamma delta T cells can recognize naturally occurring small non-peptidic antigens.

Apoptosis occurs predominantly in bystander cells and not in productively infected cells of HIV- and SIV-infected lymph nodes.

Abstract: Although 13 years have passed since identification of human immunodeficiency virus-1 (HIV-1) as the cause of AIDS, we do not yet know how HIV kills its primary target, the T cell that carries the CD4 antigen. We and others have shown an increase in the percentage of apoptotic cells among circulating CD4+ (and CD8+) T cells of HIV-seropositive individuals and an increase in frequency of apoptosis with disease progression. However, it is not known if this apoptosis occurs in infected or uninfected T cells. We show here, using in situ labelling of lymph nodes from HIV-infected children and SIV-infected macaques, that apoptosis occurs predominantly in bystander cells and not in the productively infected cells themselves. These data have implications for pathogenesis and therapy, namely, arguing that rational drug therapy may involve combination agents targeting viral replication in infected cells and apoptosis of uninfected cells.

Fas ligand mediates activation-induced cell death in human T lymphocytes.

Abstract: A significant proportion of previously activated human T cells undergo apoptosis when triggered through the CD3/T cell receptor complex, a process termed activation-induced cell death (AICD). Ligation of Fas on activated T cells by either Fas antibodies or recombinant human Fas-ligand (Fas-L) also results in cytolysis. We demonstrate that these two pathways of apoptosis are causally related. Stimulation of previously activated T cells resulted in the expression of Fas-L mRNA and lysis of Fas-positive target cells. Fas-L antagonists inhibited AICD of T cell clones and staphylococcus enterotoxin B (SEB)-specific T cell lines. The data indicate AICD in previously stimulated T cells is mediated by Fas/Fas-L interactions.

CD1 recognition by mouse NK1+ T lymphocytes

Abstract: Rare major histocompatibility complex (MHC) class I-like CD1-specific T cells have been isolated from human blood, but it has not been determined whether these clones are part of a defined subset of CD1-specific T cells selected during T cell development, or whether their recognition of CD1 is a fortuitous cross-reaction. In mice, an entire subset of alpha beta thymocytes with a unique phenotype was found to be CD1-specific. This particular subset, and its human counterpart, provide evidence that CD1 has a general role in selecting and interacting with specialized alpha beta T cells.

Deregulated T cell activation and autoimmunity in mice lacking interleukin-2 receptor beta

Abstract: In mice lacking the interleukin-2 receptor beta chain (IL-2R beta), T cells were shown to be spontaneously activated, resulting in exhaustive differentiation of B cells into plasma cells and the appearance of high serum concentrations of immunoglobulins G1 and E as well as autoantibodies that cause hemolytic anemia. Marked infiltrative granulocytopoiesis was also apparent, and the animals died after about 12 weeks. Depletion of CD4+ T cells in mutant mice rescued B cells without reversion of granulocyte abnormalities. T cells did not proliferate in response to polyclonal activators, nor could antigen-specific immune responses be elicited. Thus, IL-2R beta is required to keep the activation programs of T cells under control, to maintain homeostasis, and to prevent autoimmunity.

The effect of antigen dose on CD4+ T helper cell phenotype development in a T cell receptor-alpha beta-transgenic model.

Abstract: The dose of foreign antigen can influence whether a cell-mediated or humoral class of immune response is elicited, and this may be largely accounted for by the development of CD4+ T helper cells (Th) producing distinct sets of cytokines. The ability of antigen dose to direct the development of a Th1 or Th2 phenotype from naive CD4+ T cells, however, has not been demonstrated. In this report, we show that the antigen dose used in primary cultures could directly affect Th phenotype development from naive DO11.10 TCR-alpha beta-transgenic CD4+ T cells when dendritic cells or activated B cells were used as the antigen-presenting cells. Consistent with our previous findings, midrange peptide doses (0.3-0.6 microM) directed the development of Th0/Th1-like cells, which produced moderate amounts of interferon gamma (IFN-gamma). As the peptide dose was increased, development of Th1-like cells producing increased amounts of IFN-gamma was initially observed. At very high (> 10 microM) and very low (< 0.05 microM) doses of antigenic peptide, however, a dramatic switch to development of Th2-like cells that produced increasing amounts of interleukin 4 (IL-4) and diminishing levels of IFN-gamma was observed. This was true even when highly purified naive, high buoyant density CD4+ LECAM-1hi T cells were used, ruling out a possible contribution from contaminating "memory" phenotype CD4+ T cells. Neutralizing anti-IL-4 antibodies completely inhibited the development of this Th2-like phenotype at both high and low antigen doses, demonstrating a requirement for endogenous IL-4. Our findings suggest that the antigen dose may affect the levels of endogenous cytokines such as IL-4 in primary cultures, resulting in the development of distinct Th cell phenotypes.

CD1-restricted T cell recognition of microbial lipoglycan antigens.

Abstract: It has long been the paradigm that T cells recognize peptide antigens presented by major histocompatibility complex (MHC) molecules. However, nonpeptide antigens can be presented to T cells by human CD1b molecules, which are not encoded by the MHC. A major class of microbial antigens associated with pathogenicity are lipoglycans. It is shown here that human CD1b presents the defined mycobacterial lipoglycan lipoarabinomannan (LAM) to alpha beta T cell receptor-bearing lymphocytes. Presentation of these lipoglycan antigens required internalization and endosomal acidification. The T cell recognition required mannosides with alpha(1-->2) linkages and a phosphotidylinositol unit. T cells activated by LAM produced interferon gamma and were cytolytic. Thus, an important class of microbial molecules, the lipoglycans, is a part of the universe of foreign antigens recognized by human T cells.

Progesterone favors the development of human T helper cells producing Th2-type cytokines and promotes both IL-4 production and membrane CD30 expression in established Th1 cell clones.

Abstract: The effect of progesterone (P) on the cytokine production profile of Ag-specific human CD4+ T cell lines and clones was investigated. T cell lines specific for purified protein derivative or streptokinase (SK) derived in the presence of P exhibited significant increased ability to produce IL-5 in comparison with T cell lines derived in the absence of P. Moreover, IL-4 was significantly increased in SK-specific T cell lines derived in the presence of P in comparison with SK-specific T cell lines derived in the absence of this hormone. In addition, SK-specific T cell lines generated in the presence of P developed into T cell clones showing a Th0-, instead of Th1-like, cytokine profile. Furthermore, SK-specific T cell clones with an established Th1 profile of cytokine secretion did express mRNA for, and produced detectable amounts of, IL-4 when stimulated with P in combination with insoluble anti-CD3 mAb. Combined stimulation with P and insoluble anti-CD3 mAb also enabled Th1 clones to express CD30 on their surface membrane. These results indicate that P can favor the development of Th cells producing Th2-type cytokines and is an inducer of both transient IL-4 production and CD30 expression in established Th1 cells. Thus, P production at the placental level may be responsible, at least in part, for increased production of Th2-type cytokines which have been implied in fetal allograft survival and maintenance of successful pregnancy.

Mechanisms of phosphatidylserine exposure, a phagocyte recognition signal, on apoptotic T lymphocytes.

Abstract: The appearance of phosphatidylserine (PS) on the cell surface during apoptosis in thymocytes and cytotoxic T lymphocyte cell lines provokes PS-dependent recognition by activated macrophages. Flow cytometric analysis of transbilayer lipid movements in T lymphocytes undergoing apoptosis reveals that downregulation of the adenosine triphosphate-dependent amino-phospholipid translocase and activation of a nonspecific lipid scramblase are responsible for PS reaching the surface from its intracellular location. Both mechanisms are expressed at the same time, and precede DNA degradation, zeiosis, and cell lysis in the apoptotic pathway.

Activation of the apoptotic protease CPP32 by cytotoxic T-cell-derived granzyme B

Abstract: CYTOTOXIC T lymphocyte (CTL)-mediated cytotoxicity represents the body's major defence against virus-infected and tumorigenic cells, and contributes to transplant rejection and autoimmune disease. During killing, CTL granules are exocytosed, releasing their contents into the intercellular space between the target cell and the effector. Perform facilitates the entry of cytotoxic cell serine proteases, the granzymes, into the target cell, where they induce apoptotic death by an unknown pathway1. Granzyme B is essential for the induction of DNA fragmentation and apoptosis in target cells2-5, yet its substrate is unknown. Identification of the intracellular substrate for granzyme B is therefore the key to understanding the mechanism of CTL-mediated killing. Here we show that granzyme B cleaves and activates CPP32, the precursor of the protease responsible for cleavage of poly(ADP-ribose) polymerase.

Extent of T cell receptor ligation can determine the functional differentiation of naive CD4+ T cells.

Abstract: Naive CD4+ T cells can differentiate into cells predominantly involved in humoral immunity, known as T helper type 2 cells (Th2), or cells involved in cell-mediated immunity, known as Th1 cells. In this report, we show that priming of CD4+ T cells bearing a transgene-encoded T cell receptor can lead to differentiation into Th1-like cells producing abundant interferon gamma when the cells are exposed to high antigen doses, while low doses of the same peptide induce cells with the same T cell receptor to differentiate into Th2-like cells producing abundant interleukin 4. Thus antigen dose is one factor that can control the differentiation fate of a naive CD4+ T cell.

Kinetics of Gag-specific cytotoxic T lymphocyte responses during the clinical course of HIV-1 infection: a longitudinal analysis of rapid progressors and long-term asymptomatics.

Abstract: To gain more insight into the role of HIV-1-specific cytotoxic T lymphocytes (CTL) in the pathogenesis of AIDS, we investigated temporal relations between HIV-1 Gag-specific precursor CTL (CTLp), HIV-1 viral load, CD4+ T cell counts, and T cell function. Six HIV-1-infected subjects, who were asymptomatic for more than 8 yr with CD4+ counts > 500 cells/mm3, were compared with six subjects who progressed to AIDS within 5 yr after HIV-1 seroconversion. In the long-term asymptomatics, persistent HIV-1 Gag-specific CTL responses and very low numbers of HIV-1-infected CD4+ T cells coincided with normal and stable CD4+ counts and preserved CD3 mAb-induced T cell reactivity for more than 8 yr. In five out of six rapid progressors Gag-specific CTLp were also detected. However, early in infection the number of circulating HIV-1-infected CD4+ T cells increased despite strong and mounting Gag-specific CTL responses. During subsequent clinical progression to AIDS, loss of Gag-specific CTLp coincided with precipitating CD4+ counts and severe deterioration of T cell function. The possible relationships of HIV-1 Gag-specific CTLp to disease progression are discussed.

Monoclonal antibodies directed to the HER2 receptor

Abstract: A method of inhibiting growth of tumor cells which overexpress a growth factor receptor or growth factor by treatment of the cells with antibodies which inhibit the growth factor receptor function, is disclosed. A method of treating tumor cells with antibodies which inhibit growth factor receptor function, and with cytotoxic factor(s) such as tumor necrosis factor, is also disclosed. By inhibiting growth factor receptor functions tumor cells are rendered more susceptible to cytotoxic factors.

Interleukin 12 signaling in T helper type 1 (Th1) cells involves tyrosine phosphorylation of signal transducer and activator of transcription (Stat)3 and Stat4.

Abstract: Interleukin 12 (IL-12) initiates the differentiation of naive CD4+ T cells to T helper type 1 (Th1) cells critical for resistance to intracellular pathogens such as Leishmania major. To explore the basis of IL-12 action, we analyzed induction of nuclear factors in Th1 cells. IL-12 selectively induced nuclear DNA-binding complexes that contained Stat3 and Stat4, recently cloned members of the family of signal transducers and activators of transcription (STATs). While Stat3 participates in signaling for several other cytokines, Stat4 was not previously known to participate in the signaling pathway for any natural ligand. The selective activation of Stat4 provides a basis for unique actions of IL-12 on Th1 development. Thus, this study presents the first identification of the early events in IL-12 signaling in T cells and of ligand activation of Stat4.

Expression of the functional soluble form of human fas ligand in activated lymphocytes.

Abstract: Fas is a type I membrane protein which mediates apoptosis. Fas ligand (FasL) is a 40 kDa type II membrane protein expressed in cytotoxic T cells upon activation that belongs to the tumor necrosis factor (TNF) family. Here, we found abundant cytotoxic activity against Fas-expressing cells in the supernatant of COS cells transfected with human FasL cDNA but not with murine FasL cDNA. Using a specific polyclonal antibody against a peptide in the extracellular region of human FasL, a protein of 26 kDa was detected in the supernatant of the COS cells. The signal sequence of granulocyte colony-stimulating factor was attached to the extracellular region of human FasL. COS cells transfected with the cDNA coding for the chimeric protein efficiently secreted the active soluble form of human FasL (sFasL). Chemical crosslinking and gel filtration analysis suggested that human sFasL exists as a trimer. Human peripheral T cells activated with phorbol myristic acetate and ionomycin also produced functional sFasL, suggesting that human sFasL works as a pathological agent in systemic tissue injury.

Differential production of interferon-gamma and interleukin-4 in response to Th1- and Th2-stimulating pathogens by gamma delta T cells in vivo

Abstract: Exposure to various pathogens can stimulate at least two patterns of cytokine production by CD4-positive T cells. Responses that result in secretion of interferon-gamma (IFN-gamma), lymphotoxin and interleukin-2 (IL-2) are classified as T-helper-1 (Th1); CD4+ T-cell production of IL-4, IL-5, IL-9, IL-10 and IL-13 is called a T-helper-2 response (Th2). Differentiation of CD4+ T cells into either Th1 or Th2 cells is influenced by the cytokine milieu in which the initial antigen priming occurs. Here we use flow cytometry to identify the presence of intracellular cytokines (cytoflow) and analyse T-cell production of IFN-gamma and IL-4 from mice infected with Listeria monocytogenes or Nippostrongylus brasiliensis. We show that T cells bearing gamma delta receptors discriminate early in infection between these two pathogens by producing cytokines associated with the appropriate T-helper response. Our results demonstrate that gamma delta T cells are involved in establishing primary immune responses.