Showing papers on "Cytotoxic T cell published in 1991"
TL;DR: It is indicated that IL-10 and v-IL-10 can completely prevent antigen-specific T cell proliferation by inhibition of the antigen-presenting capacity of monocytes through downregulation of class II MHC antigens on monocytes.
Abstract: Interleukin 10 (IL-10) and viral IL-10 (v-IL-10) strongly reduced antigen-specific proliferation of human T cells and CD4+ T cell clones when monocytes were used as antigen-presenting cells. In contrast, IL-10 and v-IL-10 did not affect the proliferative responses to antigens presented by autologous Epstein-Barr virus-lymphoblastoid cell line (EBV-LCL). Inhibition of antigen-specific T cell responses was associated with downregulation of constitutive, as well as interferon gamma- or IL-4-induced, class II MHC expression on monocytes by IL-10 and v-IL-10, resulting in the reduction in antigen-presenting capacity of these cells. In contrast, IL-10 and v-IL-10 had no effect on class II major histocompatibility complex (MHC) expression on EBV-LCL. The reduced antigen-presenting capacity of monocytes correlated with a decreased capacity to mobilize intracellular Ca2+ in the responder T cell clones. The diminished antigen-presenting capacities of monocytes were not due to inhibitory effects of IL-10 and v-IL-10 on antigen processing, since the proliferative T cell responses to antigenic peptides, which did not require processing, were equally well inhibited. Furthermore, the inhibitory effects of IL-10 and v-IL-10 on antigen-specific proliferative T cell responses could not be neutralized by exogenous IL-2 or IL-4. Although IL-10 and v-IL-10 suppressed IL-1 alpha, IL-1 beta, tumor necrosis factor alpha (TNF-alpha), and IL-6 production by monocytes, it was excluded that these cytokines played a role in antigen-specific T cell proliferation, since normal antigen-specific responses were observed in the presence of neutralizing anti-IL-1, -IL-6, and -TNF-alpha mAbs. Furthermore, addition of saturating concentrations of IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha to the cultures had no effect on the reduced proliferative T cell responses in the presence of IL-10, or v-IL-10. Collectively, our data indicate that IL-10 and v-IL-10 can completely prevent antigen-specific T cell proliferation by inhibition of the antigen-presenting capacity of monocytes through downregulation of class II MHC antigens on monocytes.
1,981 citations
TL;DR: These findings provide direct evidence that, like its structural homologue CD28, CTLA- 4 is able to bind the B7 counter-receptor on activated B cells.
Abstract: Functional interactions between T and B lymphocytes are necessary for optimal activation of an immune response. Recently, the T lymphocyte receptor CD28 was shown to bind the B7 counter-receptor on activated B lymphocytes, and subsequently to costimulate interleukin 2 production and T cell proliferation. CTLA-4 is a predicted membrane receptor from cytotoxic T cells that is homologous to CD28 and whose gene maps to the same chromosomal band as the gene for CD28. It is not known, however, if CD28 and CTLA-4 also share functional properties. To investigate functional properties of CTLA-4, we have produced a soluble genetic fusion between the extracellular domain of CTLA-4 and an immunoglobulin C gamma chain. Here, we show that the fusion protein encoded by this construct, CTLA4Ig, bound specifically to B7-transfected Chinese hamster ovary cells and to lymphoblastoid cells. CTLA4Ig also immunoprecipitated B7 from cell surface 125I-labeled extracts of these cells. The avidity of 125I-labeled B7Ig fusion protein for immobilized CTLA4Ig was estimated (Kd approximately 12 nM). Finally, we show that CTLA4Ig was a potent inhibitor of in vitro immune responses dependent upon cellular interactions between T and B lymphocytes. These findings provide direct evidence that, like its structural homologue CD28, CTLA-4 is able to bind the B7 counter-receptor on activated B cells. Lymphocyte interactions involving the B7 counter-receptor are functionally important for alloantigen responses in vitro.
1,756 citations
TL;DR: It is demonstrated that the CD28 signaling pathway could be activated by B7, resulting in increased T cell cytokine production and T cell proliferation, and costimulatory for T cell activation.
Abstract: A successful immune response requires intercellular contact between T and B lymphocytes. We recently showed that CD28, a T cell surface protein that regulates an activation pathway, could mediate intercellular adhesion with activated B cells by interaction with the B7 antigen. Here we show that CD28 is the primary receptor for B7 on activated peripheral blood T cells, that CD28 binds to B7 in the absence of other accessory molecules, and that interaction between CD28 and B7 is costimulatory for T cell activation. To characterize the binding of CD28 to B7, we have produced genetic fusions of the extracellular portions of B7 and CD28, and immunoglobulin (Ig) C gamma 1 chains. 125I-labeled B7 Ig bound to CD28-transfected Chinese hamster ovary (CHO) cells, and to immobilized CD28 Ig with a Kd approximately 200 nM. B7 Ig also inhibited CD28-mediated cellular adhesion. The function of CD28-B7 interactions during T cell activation was investigated with soluble fusion proteins and with B7-transfected CHO cells. Immobilized B7 Ig and B7+ CHO cells costimulated T cell proliferation. Stimulation of T cells with B7+ CHO cells also specifically increased levels of interleukin 2 transcripts. These results demonstrate that the CD28 signaling pathway could be activated by B7, resulting in increased T cell cytokine production and T cell proliferation. Cellular interactions mediated by B7 and CD28 may represent an important component of the functional interactions between T and B lymphoid cells.
1,254 citations
TL;DR: This model indicates that self-reactive cytotoxic T cells may remain functionally unresponsive, owing to a lack of appropriate T cell activation, in so-called "T cell-mediated autoimmune diseases".
1,196 citations
TL;DR: It appears that key functional events are emerging in the pathogenesis of HIV-1 infection leading to AIDS and that monitoring of these events is practical; there is a sense of urgency about these studies: they hold clues for the diagnosis, prevention and therapy of AIDS.
1,109 citations
TL;DR: It is suggested that modulated bcl-2 expression is a determinant of life and death in normal lymphocytes in mice expressing an E mu-bCl-2 transgene within the T lymphoid compartment.
1,103 citations
TL;DR: Functional subsets of human T cells were delineated by analyzing patterns of lymphokines produced by clones from individuals with leprosy and by T cell clones of known function, and interleukin-4 was found to be necessary for suppression in vitro.
Abstract: Functional subsets of human T cells were delineated by analyzing patterns of lymphokines produced by clones from individuals with leprosy and by T cell clones of known function CD4 clones from individuals with strong cell-mediated immunity produced predominantly interferon-gamma, whereas those clones that enhanced antibody formation produced interleukin-4 CD8 cytotoxic T cells secreted interferon-gamma Interleukin-4 was produced by CD8 T suppressor clones from immunologically unresponsive individuals with leprosy and was found to be necessary for suppression in vitro Both the classic reciprocal relation between antibody formation and cell-mediated immunity and resistance or susceptibility to certain infections may be explained by T cell subsets differing in patterns of lymphokine production
1,052 citations
TL;DR: In a longitudinal study of HIV seropositive patients, there were fluctuations in the specificity of cytotoxic T cells for the virus, matched by variability in proviral gag DNA epitope sequences in the lymphocytes of these patients.
Abstract: In a longitudinal study of HIV seropositive patients, there were fluctuations in the specificity of cytotoxic T cells for the virus. This was matched by variability in proviral gag DNA epitope sequences in the lymphocytes of these patients. Some of these viral variants are not recognized by autologous T cells. Accumulation of such mutations in T-cell antigenic targets would provide a mechanism for immune escape.
1,034 citations
TL;DR: Investigation of the individual roles of the murine type 1 and type 2 tumor necrosis factor (TNF) receptors suggest that TNF-R2 initiates signals for the proliferation of thymocytes and cytotoxicity and the induction of the protective activity, manganous superoxide dismutase.
Abstract: The individual roles of the murine type 1 and type 2 tumor necrosis factor (TNF) receptors (TNF-R1 and TNF-R2) were investigated utilizing (i) the strong species specificity of TNF-R2 for murine TNF compared to human TNF and (ii) agonistic rabbit polyclonal antibodies directed against the individual TNF receptors. Proliferation of mouse thymocytes and the murine cytotoxic T-cell line CT-6 is stimulated by murine TNF but not by human TNF. Consistent with this observation, polyclonal antibodies directed against TNF-R2 induced proliferation in both of these cell types, whereas polyclonal antibodies directed against TNF-R1 had no effect. In contrast, cytotoxicity in murine LM cells (which are sensitive to murine and human TNF) was induced by antibodies against TNF-R1 but not by antibodies against TNF-R2. Also, the steady-state level of manganous superoxide dismutase mRNA in the murine NIH 3T3 cell line was induced by murine TNF, human TNF, and anti-TNF-R1 but not by anti-TNF-R2. These results suggest that TNF-R2 initiates signals for the proliferation of thymocytes and cytotoxic T cells, whereas TNF-R1 initiates signals for cytotoxicity and the induction of the protective activity, manganous superoxide dismutase. The nonredundant signaling observed for the two TNF receptors cannot be explained simply by the differential expression of the two TNF receptors in the various cell types, because LM cells express on their surface higher levels of TNF-R2 than TNF-R1, and LM cells, NIH 3T3 cells, and thymus cells all express mRNA corresponding to both receptor types. It is therefore likely that the two receptors initiate distinct signaling pathways that result in the induction of different cellular responses.
877 citations
TL;DR: In these mice, the development of CD8+ T cells and myeloid components is unaltered, indicating that expression of CD4 on progenitor cells and CD4+CD8+ (double positive) thymocytes is not obligatory, which is important to the understanding of immune disorders, including AIDS.
Abstract: T CELLS express T-cell antigen receptors (TCR) for the recognition of antigen in conjunction with the products of the major histocompatibility complex1,2. They also express two key surface coreceptors, CD4 and CDS, which are involved in the interaction with their ligands3,4. As CD4 is expressed on the early haemopoietic progenitor5 as well as the early thymic precursor cells6, a role for CD4 in haemopoiesis and T-cell development is implicated. Thymocytes undergo a series of differentiation7 and selection steps8,9 to become mature CD4+8− or CD4−8+ (single positive) T cells10,11. Studies of the role of CD4+ T cells in vivo have been based on adoptive transfer of selected or depleted lymphocytes, or in vivo treatment of thymectomized mice with monoclonal antibodies causing depletion of CD4+ T cells12–14. In order to study the role of the CD4 molecule in the development and function of lymphocytes, we have disrupted the CD4 gene in embryonic stem cells15–16 by homologous recombination17–18. Germ-line transmission19–20 of the mutation produces mutant mouse strains that do not express CD4 on the cell surface. In these mice, the development of CD8+ T cells and myeloid components is unaltered, indicating that expression of CD4 on progenitor cells and CD4+ CD8+ (double positive) thymocytes is not obligatory. Here we report that these mice have markedly decreased helper cell activity for antibody responses, although cytotoxic T-cell activity against viruses is in the normal range. This differential requirement for CD4+ helper T cells is important to our understanding of immune disorders, including AIDS, in which CD4+ cells are reduced or absent.
705 citations
TL;DR: It is demonstrated that restoration of CMV-specific CTL responses may require an extended time period after BMT in some patients, and that such patients are at increased risk of developing severe CMV disease.
TL;DR: In this article, the subcellular localization of perforin, granzymes, and known endosomal and lysosomal marker proteins was determined in human and murine CTL, by immunogold labeling of ultrathin cryosections followed by electron microscopy.
Abstract: Cytotoxic T lymphocytes (CTL) contain granules that are exocytosed during specific interaction with target cells (TC). In this process, the granule contents, including the lethal protein perforin, as well as granzymes, a family of serine esterases, are delivered to the TC. Information regarding the routing of these proteins towards the granule and their exact localization within the granule is of primary importance to resolve the mechanism of granule-mediated TC killing. In this study, the subcellular localization of perforin, granzymes, and known endosomal and lysosomal marker proteins was determined in human and murine CTL, by immunogold labeling of ultrathin cryosections followed by electron microscopy. Perforin and granzymes can be detected in rough endoplasmic reticulum, Golgi complex, trans-Golgi reticulum, and in all cytotoxic granules. Within the granules, they have a similar distribution and are localized not only in the so-called dense core but also over the region containing small internal vesicles. This finding implies that perforin and granzymes can be released in membrane-enveloped and/or -associated form into the intercellular cleft formed upon CTL-TC interaction. On the basis of the present evidence, additional release of these molecules in soluble form cannot be excluded. The lysosomal membrane glycoproteins lamp-1, lamp-2, and CD63, are abundantly present on the granule-delimiting outer membrane, which becomes incorporated into the CTL plasma membrane during lethal hit delivery. In contrast, the cation-dependent mannose 6-phosphate receptor, known to be present in endosomes and absent from lysosomes, is found only in a minority of the granules. Together with our previous findings that the granules are acidic and connected to the endocytic pathway, these observations define CTL granules as secretory lysosomes.
TL;DR: In this article, the maturation of T cells in the thymus is dependent on the expression of major histocompatibility complex (MHC) molecules, and it was shown that MHC class II-deficient mice were depleted of mature CD4+ T cells and were deficient in cell mediated immune responses.
Abstract: The maturation of T cells in the thymus is dependent on the expression of major histocompatibility complex (MHC) molecules. By disruption of the MHC class II Ab beta gene in embryonic stem cells, mice were generated that lack cell surface expression of class II molecules. These MHC class II-deficient mice were depleted of mature CD4+ T cells and were deficient in cell-mediated immune responses. These results provide genetic evidence that class II molecules are required for the maturation and function of mature CD4+ T cells.
TL;DR: Peripheral selection was found to be dependent on T cell receptor (TCR)-ligand interactions but to differ from thymic selection with regard to specificity and mechanism.
Abstract: T lymphocytes undergo selection events not only in the thymus, but also after they leave the thymus and reside in the periphery Peripheral selection was found to be dependent on T cell receptor (TCR)-ligand interactions but to differ from thymic selection with regard to specificity and mechanism Unlike thymic selection, peripheral selection required binding of antigen to the TCR, and it induced expansion of T cell clones Tolerance to self antigens that are restricted to the periphery occurred through the elimination of self-reactive T cells and by the clonal anergy, which was associated with down-regulation of the alpha beta TCR and CD8
TL;DR: This chapter attempts to identify the principles and issues elucidated in animal models that may provide insights for the development of effective approaches to modulate T cell functions to promote the eradication of human tumors.
Abstract: Publisher Summary This chapter attempts to identify the principles and issues elucidated in animal models that may provide insights for the development of effective approaches to modulate T cell functions to promote the eradication of human tumors. The importance of T cells in surveillance against the outgrowth of tumor cells is probably best demonstrated with virally transformed tumors, such as EBV-induced B cell lymphomas, which occur with markedly increased frequency in transplant patients specifically depleted of T cells, and with UV-induced squamous cell cancers that occur with high frequency in renal transplant patients. Second, the reasons for the growth of presumably immunogenic tumors in immunocompetent hosts have become more apparent with an improved understanding of the function of T cell subsets and the requirements for the induction and expression of T cell responses. The earlier perceptions that cytotoxic T cells recognize foreign proteins integrally inserted in the cell membrane had focused efforts for more than a decade on the use of the powerful new monoclonal antibody technology combined with biochemical purification techniques to isolate tumor antigens expressed on the cell membrane. However, analyses of the requirements for recognition of virally infected cells by CD8 + cytotoxic T cells demonstrated that Class I-restricted T c do not recognize integral membrane proteins but rather recognize intracellular proteins that are synthesized in the cytoplasm. Tumors containing unique or mutated and potentially immunogenic cellular proteins may selectively or predominantly elicit only CD4 + or CD8 + T cell responses because the antigen is adequately presented in the context of only one MHC molecule, and in this setting only T cells from the subset restricted to that MHC molecule appear effective in tumor therapy.
TL;DR: Quiescent T lymphocytes may be a major and inducible HIV-1 reservoir in infected individuals and an increase in integrated relative to extrachromosomal DNA forms in patients with acquired immunodeficiency syndrome (AIDS) was investigated.
Abstract: To better understand the basis for human immunodeficiency virus type 1 (HIV-1) persistence and latency, the form in which viral DNA exists in the peripheral T lymphocyte reservoir of infected individuals was investigated. In asymptomatic individuals, HIV-1 was harbored predominantly as full-length, unintegrated complementary DNA. These extrachromosomal DNA forms retained the ability to integrate upon T cell activation in vitro. In patients with acquired immunodeficiency syndrome (AIDS), there was an increase in integrated relative to extrachromosomal DNA forms. By analysis of DNA from patient lymphocyte subpopulations depleted of human lymphocyte antigen-Dr receptor-positive cells, quiescent T cells were identified as the source of extrachromosomal HIV-1 DNA. Thus quiescent T lymphocytes may be a major and inducible HIV-1 reservoir in infected individuals.
Journal Article•
TL;DR: Like anti-CD28 mAb, autologous human APC appeared to stimulate a cyclosporine A-resistant pathway of T cell activation and suggest that the two signals required for IL-2 production by CD4+ T cells can be transduced by the TCR and CD28.
Abstract: CD4+ T cells require two signals to produce maximal amounts of IL-2, ie, TCR occupancy and an unidentified APC-derived costimulus Here we show that this costimulatory signal can be delivered by the T cell molecule CD28 An agonistic anti-CD28 mAb, but not IL-1 and/or IL-6, stimulated T cell proliferation by tetanus toxoid-specific T cells cultured with Ag-pulsed, costimulation-deficient APC Furthermore, the ability of B cell tumor lines to provide costimulatory signals to purified T cells correlated well with expression of the CD28 ligand B7/BB-1 Finally, like anti-CD28 mAb, autologous human APC appeared to stimulate a cyclosporine A-resistant pathway of T cell activation Together, these results suggest that the two signals required for IL-2 production by CD4+ T cells can be transduced by the TCR and CD28
TL;DR: Interestingly, despite their high cytotoxic activity against lymphoma cells, these cells had little toxicity against a subset of normal human hematopoietic precursor cells (granulocyte/macrophage colony-forming units).
Abstract: C.B-17 severe combined immune deficient (SCID) mice, which lack functional B and T lymphocytes, allow xenografts and, therefore, can be used to study the biology of human malignancies. Two different human B cell lymphoma cell lines, SU-DHL-4 and OCI-Ly8, which both harbor the t(14;18) chromosomal translocation, were injected into C.B-17 SCID mice. Mice injected intravenously or intraperitoneally developed tumors and died in a dose-dependent manner. The presence of tumor cells in various murine tissues could be demonstrated by a clonogenic tumor assay, staining of frozen sections with a monoclonal antibody (mAb) against a human B cell antigen (CD19), and with the polymerase chain reaction technique. A protocol using cytotoxic effector cells was developed and used to selectively deplete the tumor cells from bone marrow. These cells were developed by growing peripheral blood mononuclear cells in the presence of interferon gamma (IFN-gamma), anti-CD3 mAb, and interleukin 2 (IL-2). The timing of IFN-gamma treatment was critical and optimal if IFN-gamma was added before IL-2 treatment. The cells that were stimulated by IFN-gamma, followed by IL-2, could be expanded by treatment with a mAb directed against CD3. These cells could be further activated by IL-1, but not by tumor necrosis factor alpha. With this protocol, a tumor cell kill of 3 logs was obtained as measured by a clonogenic assay. Interestingly, despite their high cytotoxic activity against lymphoma cells, these cells had little toxicity against a subset of normal human hematopoietic precursor cells (granulocyte/macrophage colony-forming units). These cells were further tested by treating murine bone marrow contaminated with the human lymphoma cell line SU-DHL-4, and injecting these cells into SCID mice to assay for tumor growth in vivo. The animals injected with bone marrow contaminated with SU-DHL-4 cells had enhanced survival if the bone marrow was treated with the cytokine-induced killer cells before infusion. The SCID mouse provides a useful in vivo model for evaluation of new therapeutic approaches for lymphoma treatment. The cytokine-induced killer cells generated as described here could have an important impact on bone marrow purging for autologous bone marrow transplantation as well as for adoptive immunotherapy.
TL;DR: In the presence of antigen presenting cells, a murine T helper cell specific for murine hemoglobin responded to its immunogenic peptide by both cytokine (interleukin-4) secretion and proliferation and an altered peptide with a single amino acid substitution induced only cytokine secretion and did not induce proliferation.
Abstract: In the presence of antigen presenting cells, a murine T helper (Th) cell specific for murine hemoglobin (Hb) responded to its immunogenic peptide by both cytokine (interleukin-4) secretion and proliferation. An altered Hb peptide with a single amino acid substitution induced only cytokine secretion and did not induce proliferation. Interleukin-1 costimulated and restored the Th proliferative response to normal levels. The altered peptide also supported cognate T cell-B cell interactions indicative of T cell helper function. Thus, this result suggests that the T cell receptor has the capacity of differential signaling.
TL;DR: The results indicate that down-regulation of TCR and CD8 molecules on the antigen-specific T cells is a novel mechanism, by which peripheral tolerance to this antigen can occur.
TL;DR: It is suggested that CD8 is necessary for the maturation and positive selection of class I MHCrestricted cytotoxic T lymphocytes but is not required on any of the intermediate thymocyte populations during the development of functional class II MHC restricted helper T cells.
TL;DR: Results confirm the importance of TNF-alpha in the pathogenesis of septic shock and suggest a clinical potential for TNFR-IgG as a preventive and therapeutic treatment in sepsis.
Abstract: Tumor necrosis factors (TNF) alpha and beta are structurally related cytokines that mediate a wide range of immunological, inflammatory, and cytotoxic effects. During bacterial infection of the bloodstream (sepsis), TNF-alpha induction by bacterial endotoxin is thought to be a major factor contributing to the cardiovascular collapse and critical organ failure that can develop. Despite antibiotic therapy, these consequences of sepsis continue to have a high mortality rate in humans. Here we describe a potent TNF antagonist, a TNF receptor (TNFR) immunoadhesin, constructed by gene fusion of the extracellular portion of human type 1 TNFR with the constant domains of human IgG heavy chain (TNFR-IgG). When expressed in transfected human cells, TNFR-IgG is secreted as a disulfide-bonded homodimer. Purified TNFR-IgG binds to both TNF-alpha and TNF-beta and exhibits 6- to 8-fold higher affinity for TNF-alpha than cell surface or soluble TNF receptors. In vitro, TNFR-IgG blocks completely the cytolytic effect of TNF-alpha or TNF-beta on actinomycin D-treated cells and is markedly more efficient than soluble TNFR (24-fold) or monoclonal anti-TNF-alpha antibodies (4-fold) in inhibiting TNF-alpha. In vitro, TNFR-IgG prevents endotoxin-induced lethality in mice when given 0.5 hr prior to endotoxin and provides significant protection when given up to 1 hr after endotoxin challenge. These results confirm the importance of TNF-alpha in the pathogenesis of septic shock and suggest a clinical potential for TNFR-IgG as a preventive and therapeutic treatment in sepsis.
TL;DR: B7-transfected CHO cells can induce suboptimally activated CD28+ T cells to proliferate and secrete high levels of interleukin 2, and this response is identical whether T cells are submitogenically stimulated with either phorbol myristate acetate or anti-CD3 to activate the T cells.
Abstract: Occupancy of the T-cell receptor complex does not appear to be a sufficient stimulus to induce a T-cell-mediated immune response. Increasing evidence suggests that cognate cell-cell interaction between an activated T cell and an antigen-presenting cell may provide such a stimulus. A candidate T-cell surface molecule for this costimulatory signal is the T-cell-restricted CD28 antigen. Following crosslinking with anti-CD28 mAb, suboptimally stimulated CD28+ T cells show increased proliferation and markedly increased secretion of a subset of lymphokines. Recently, the B-cell surface activation antigen B7 was shown to be a natural ligand for the CD28 molecule, and both B7 and CD28 are members of the immunoglobulin superfamily. Here we report that B7-transfected CHO cells can induce suboptimally activated CD28+ T cells to proliferate and secrete high levels of interleukin 2. The response is identical whether T cells are submitogenically stimulated with either phorbol myristate acetate or anti-CD3 to activate the T cells. This response is specific and can be totally abrogated with anti-B7 monoclonal antibody. As has previously been observed for anti-CD28 monoclonal antibody, B7 ligation induced secretion of interleukin 2 but not interleukin 4. We have previously demonstrated that B7 expression is restricted to activated B lymphocytes and interferon gamma-activated monocytes. Since these two cellular populations are involved in antigen presentation as well as cognate interaction with T lymphocytes, B7 is likely to represent a central constimulatory signal that is capable of amplifying an immune response.
Journal Article•
TL;DR: IL-12 is a growth factor for activated human T cells and NK cells; however, its spectrum of lymphocyte growth-promoting properties is distinct from that of IL-2, IL-4, or IL-7.
Abstract: IL-12 is a heterodimeric cytokine that was identified on the basis of its ability to synergize with IL-2 in the induction of cytotoxic effector cells and was originally called cytotoxic lymphocyte maturation factor (CLMF). IL-12 was also found to stimulate the proliferation of PHA-activated lymphoblasts which were greater than 90% CD3+ T cells. In this report we further characterize the effects of IL-12 on lymphocyte proliferation. Studies with purified subpopulations of PHA-activated lymphoblasts and with cloned lines of human T cells indicated that IL-12 caused the proliferation of activated T cells of both the CD4+ and CD8+ subsets. This effect of IL-12 was independent of IL-2 because it was not blocked by antibodies to either IL-2 or IL-2R. The maximum proliferation induced by IL-12 was 31 to 72% of the maximum caused by IL-2; however, IL-12 was active at a lower effective concentration (EC50 = 8.5 +/- 1.3 pM) than IL-2 (EC50 = 52 +/- 8 pM). Combination of suboptimal amounts of IL-12 and IL-2 resulted in additive proliferation, up to the maximum induced by IL-2 alone. IL-12 also caused the proliferation of lymphocytes activated by culture with IL-2 for 6 to 12 days. CD56+ NK cells were among the IL-12-responsive cells in the IL-2-activated lymphocyte population. Unlike IL-2 or IL-7, IL-12 caused little or no proliferation of resting peripheral blood mononuclear cells (PBMC). In this regard, IL-12 was similar to IL-4. However, IL-12 could enhance the proliferation of resting PBMC caused by suboptimal amounts of IL-2, whereas IL-4 inhibited IL-2-induced PBMC proliferation. Thus, IL-12 is a growth factor for activated human T cells and NK cells; however, its spectrum of lymphocyte growth-promoting properties is distinct from that of IL-2, IL-4, or IL-7.
TL;DR: The immune system provides good models for cell death, a phenomenon now recognized to be of fundamental importance in many fields of biology and the nature of molecules causally involved in the dying cell can now be approached in some systems.
Abstract: The immune system provides good models for cell death, a phenomenon now recognized to be of fundamental importance in many fields of biology. Cell death is strikingly polymorphic: it can proceed via necrosis (as in complement-mediated cell death) or apoptosis, but the latter displays different patterns (in the receptor-mediated death of some thymocytes, in cell death mediated by TNF alpha or by cytotoxic T cells), perhaps reflecting different pathways of control of a common core mechanism. Even though there are differences in the morphological and metabolic changes associated with the different patterns of apoptosis, some recurrent sequences of events are observed in almost all dying cells. The metabolic state of a cell often seems to play a major role in determining if and how this cell will die in given external circumstances. The nature of molecules causally involved in the dying cell can now be approached in some systems.
TL;DR: The findings suggest that cell injury is an important physiologic stimulus for release of IL-1, and the nature of the injury profoundly affects the forms ofIL-1 that are released.
Abstract: Interleukin (IL-) 1 alpha and 1 beta are synthesized as 31- to 34-kDa pro molecules. They are released from monocytes and macrophages as proteolytically processed 17-kDa mature molecules that bind with high affinity to specific receptors on target cells. IL-1 is not released via the classic secretory pathway. The pro molecules are synthesized as cytosolic proteins without signal peptides. Although the proteases that convert the pro molecules to the mature forms are cytosolic enzymes, processed IL-1 is not detected associated with the cell but is found only in culture supernatants. We demonstrate here that release of IL-1 is efficiently induced by cell injury. When the injury causes cellular necrosis, IL-1 alpha is released as a mixture of unprocessed and processed molecules but IL-1 beta is released exclusively as the biologically inactive pro form. In contrast, when cells undergo apoptosis, maturation of both IL-1 alpha and IL-1 beta is efficient. When apoptosis is rapid, as in macrophages that are targets for allospecific cytotoxic T lymphocytes, processing is observed to occur intracellularly. These findings suggest that cell injury is an important physiologic stimulus for release of IL-1. The nature of the injury profoundly affects the forms of IL-1 that are released.
TL;DR: A novel design of sCD4 molecules which exploit cytotoxic T cells as their effector function are described which induce killing of HIV‐1 infected cells.
Abstract: The human immunodeficiency virus type 1 (HIV-1) uses cell surface CD4 as a receptor to infect susceptible cells Therefore, different forms of soluble CD4 (sCD4) molecules have been developed recently for potential therapeutic purposes Here we describe a novel design of sCD4 molecules which exploit cytotoxic T cells as their effector function The principle of bispecific antibodies was exploited and further developed to create new bispecific reagents which could retarget cytotoxic T cells of any specificity and thus, induce killing of HIV-1 infected cells The most advanced molecules, Janusins, contain in one polypeptide chain the first two N-terminal CD4 domains and single chain combining site against the human CD3 complex (FvCD3)
TL;DR: The present experiments show that acute HIV-1 infection of MT2 lymphoblasts and activated normal peripheral blood mononuclear cells induces apoptosis, and the addition of anti-gp120 neutralizing antibody, after HIV-2 cells, permitted sustained high levels of viral replication, but blocked apoptosis and cell death.
Abstract: The mechanisms by which HIV-1 infection kills T lymphocytes are not clearly established. Apoptosis is an internally programmed cell death pathway that may regulate both T cell development and senescence, and that is characterized by cleavage of DNA at internucleosomal regions. The present experiments show that acute HIV-1 infection of MT2 lymphoblasts and activated normal peripheral blood mononuclear cells induces apoptosis. The addition of anti-gp120 neutralizing antibody, after HIV-1 infection of MT2 cells, permitted sustained high levels of viral replication, but blocked apoptosis and cell death. Apoptosis may account for the direct cytopathologic effects of HIV-1 in T cells.
Journal Article•
TL;DR: It is demonstrated that LT possesses potent cytotoxic activity against oligodendrocytes and that the major mechanism involved in this process is DNA fragmentation.
Abstract: The cytotoxic effect of recombinant human cytokines was tested on glial cells cultured from mature bovine brain. Lymphotoxin (LT) and TNF induced injury to oligodendrocytes in a time and dose-dependent fashion. The other cytokines tested, IFN-gamma, IL-6, and IL-2, did not affect oligodendrocytes in culture over a 72-h observation period. None of the cytokines injured astrocytes cultured from the same source. LT showed a much more potent cytotoxicity than TNF toward oligodendrocytes; cytotoxic changes were noted earlier (24 h) and at lower units of activity. Morphologic studies showed that the LT-mediated effects were associated with early retraction of cell processes, depolymerization of F-actin and subsequent nuclear degeneration. Lack of early cytoplasmic membrane injury as measured by 51Cr release and electron microscope studies demonstrating nuclear disintegration suggested an apoptotic mechanism of oligodendrocyte injury evoked by LT, which was supported by DNA integrity assay. These results demonstrate that LT possesses potent cytotoxic activity against oligodendrocytes and that the major mechanism involved in this process is DNA fragmentation.
TL;DR: A CTL clone derived from a (BALB/c x C57BL/6)F1 (H–2dxb) mouse, recognizes one of the natural epitopes derived from L. monocytogenes in an H–2Kd-restricted fashion and demonstrates the utility of the allele-specific motif for predicting CTL epitopes.
Abstract: Listeria monocytogenes is a Gram-positive bacterium which grows in the cytoplasm of eukaryotic cells and can cause severe disease in immunocompromised individuals1,2. In murine systems CD8+T lymphocytes have been shown to be important effectors of acquired protective immunity against L. monocytogenes3–5. Class I MHC-restricted CD8+ cytotoxic T lymphocytes (CTL), which lyse J774 macrophage-like targets infected with L. monocytogenes, are induced following in vivo injection of live organisms. Natural peptide epitopes derived from L. monocytogenes can be acid-extracted from heavily infected BALB/c spleens and detected by CTL. A CTL clone, B9, derived from a (BALB/c x C57BL/6)F1 (H–2dxb) mouse, recognizes one of these natural epitopes in an H–2Kd-restricted fashion. B9 also recognizes P815 (H–2d) mas-tocytoma cells transfected with the listeriolysin gene. To identify the region of the listeriolysin recognized by CTL we used the H–2Kd peptide-binding motif described by Rammensee and colleagues6 to synthesize 11 nonamer peptides. One of these peptides, listeriolysin 91–99, was recognized very efficiently by B9. This represents the first identified class I MHC-restricted epitope of bacteria and demonstrates the utility of the allele-specific motif for predicting CTL epitopes.