RESUMO
Thymic regulatory T cells (tTregs) and induced regulatory T cells (iTregs) suppress murine acute graft-versus-host disease (GVHD). Previously, we demonstrated that the plasmacytoid dendritic cell indoleamine 2,3-dioxygenase (IDO) fosters the in vitro development of human iTregs via tryptophan depletion and kynurenine (Kyn) metabolites. We now show that stimulation of naïve CD4+ T cells in low tryptophan (low Trp) plus Kyn supports human iTreg generation. In vitro, low Trp + Kyn iTregs and tTregs potently suppress T effector cell proliferation equivalently but are phenotypically distinct. Compared with tTregs or T effector cells, bioenergetics profiling reveals that low Trp + Kyn iTregs have increased basal glycolysis and oxidative phosphorylation and use glutaminolysis as an energy source. Low Trp + Kyn iTreg viability was reliant on interleukin (IL)-2 in vitro. Although in vivo IL-2 administration increased low Trp + Kyn iTreg persistence on adoptive transfer into immunodeficient mice given peripheral blood mononuclear cells to induce GVHD, IL-2-supported iTregs did not improve recipient survival. We conclude that low Trp + Kyn create suppressive iTregs that have high metabolic needs that will need to be addressed before clinical translation.
Assuntos
Transplante de Medula Óssea , Doença Enxerto-Hospedeiro/imunologia , Tolerância Imunológica/imunologia , Cinurenina/metabolismo , Linfócitos T Reguladores/imunologia , Triptofano/metabolismo , Animais , Células Cultivadas , Doença Enxerto-Hospedeiro/metabolismo , Doença Enxerto-Hospedeiro/prevenção & controle , Humanos , Técnicas In Vitro , Camundongos , Taxa de SobrevidaRESUMO
Macrophage colony-stimulating factor (M-CSF) is known to stimulate proliferation of monocyte/macrophage progenitors and enhance in vitro antitumor cytotoxicity by murine macrophages. In this paper we have shown that recombinant human M-CSF causes human peripheral blood monocytes to differentiate in culture into metabolically active macrophage-like cells. These cells mediate very efficient antibody-dependent cellular cytotoxicity (ADCC) against human melanoma and neuroblastoma cell lines in the presence of two murine IgG3 mAbs (3F8 and R24). They also mediate antibody-independent cytotoxicity (or cytostasis) to a lesser extent. Human serum had an inconsistent effect on ADCC, but often induced similar high levels of ADCC. Cytotoxicity was measured using a novel ELISA to detect surviving tumor cells after ADCC. Two conventional isotope-release assays (51Cr and [3H]TdR) underestimated or entirely failed to detect ADCC by M-CSF-activated monocytes. Optimal activation occurred with 100-300 U/ml of M-CSF, and required 9-11 d for completion. Most of the M-CSF cultured monocytes expressed the low-affinity Fc receptor (CD16). ADCC by cells of the monocyte/macrophage lineage using murine IgG3 mAbs may have significance for the immunotherapy of human malignancies.
Assuntos
Citotoxicidade Celular Dependente de Anticorpos , Fatores Estimuladores de Colônias/fisiologia , Monócitos/imunologia , Antígenos de Diferenciação/análise , Antígenos de Diferenciação Mielomonocítica/análise , Diferenciação Celular , Sobrevivência Celular , Radioisótopos de Cromo/metabolismo , Relação Dose-Resposta a Droga , Citometria de Fluxo , Gangliosídeos/imunologia , Humanos , Fragmentos Fc das Imunoglobulinas/imunologia , Fator Estimulador de Colônias de Macrófagos , Monócitos/classificação , Monócitos/citologia , Receptores Fc/análise , Receptores de IgG , Proteínas Recombinantes , Timidina/metabolismo , Células Tumorais CultivadasRESUMO
Macrophages and cultured human monocytes can mediate efficient antibody-dependent cytotoxicity (ADCC) against human tumor cells using monoclonal antibodies (mAbs). The mechanism of this killing is usually assumed to involve secreted factors (reactive oxygen intermediates, tumor necrosis factor, or other cytotoxic factors) leading to target cell lysis. In this study, we present evidence that phagocytosis of intact target cells is the principal mechanism of antitumor cytotoxicity in our in vitro model of ADCC by cultured monocytes. Human monocytes cultured in recombinant human macrophage colony-stimulating factor ingested up to 100% of fluorochrome-labeled melanoma and neuroblastoma target cells, in the presence of an appropriate antitumor mAb. Electron microscopy demonstrated phagocytosis of intact tumor cells by cultured monocytes during ADCC. All of the radionuclide in radiolabeled target cells was taken up by monocytes during phagocytosis. By preventing the release of radioisotope tracers, phagocytosis thus prevents the detection of this very efficient form of cytotoxicity by most conventional assays.
Assuntos
Citotoxicidade Celular Dependente de Anticorpos/imunologia , Fatores Estimuladores de Colônias , Monócitos/imunologia , Neoplasias/imunologia , Fagocitose/imunologia , Anticorpos Monoclonais/imunologia , Células Cultivadas , Corantes Fluorescentes , Humanos , Fator Estimulador de Colônias de Macrófagos , Monócitos/ultraestrutura , Proteínas Opsonizantes , Proteínas Recombinantes , Células Tumorais CultivadasRESUMO
Activated macrophages (M phi s) are important participants in host defense, but their uncontrolled activation leads rapidly to septic shock and death. One mechanism for regulating other dangerous cells in the immune system is programmed cell death, or apoptosis. Monocytes are known to undergo spontaneous apoptosis upon leaving the circulation unless provided with specific survival signals, but mature tissue M phi s are more robust cells, and it was not clear that they could be similarly regulated by apoptosis. We now show that during differentiation monocytes rapidly lose their sensitivity to apoptosis triggered by passive cytokine withdrawal, but they may retain a novel pathway which initiates apoptosis after activation with specific stimuli (zymosan and phorbol esters). Sensitivity to activation-induced apoptosis was developmentally determined, being downregulated by the maturation-promoting cytokine macrophage colony-stimulating factor but stably upregulated by even transient exposure to the proinflammatory cytokine interferon gamma (IFN-gamma). Apoptosis began within 2-4 h of activation, occurred in > 95% of susceptible cells, and in mixed cocultures selectively affected only those M phi s with a history of IFN-gamma priming. Consistent with a possible role for protein kinase C in the signaling pathway leading to cell death, the kinase inhibitor staurosporine was protective against both phorbol ester- and zymosan-induced apoptosis. Our studies describe a novel form of activation-induced M phi apoptosis which is developmentally regulated by two physiologically relevant cytokines. We speculate that apoptosis may serve to restrict the destructive potential of inflammatory M phi s.
Assuntos
Apoptose , Interferon gama/farmacologia , Ativação de Macrófagos , Fator Estimulador de Colônias de Macrófagos/farmacologia , Macrófagos/citologia , Dano ao DNA , Ativação Enzimática , Humanos , Técnicas In Vitro , Ativação de Macrófagos/efeitos dos fármacos , Microscopia Eletrônica , Proteína Quinase C/fisiologia , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2 , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
We have recently shown that expression of the enzyme indoleamine 2, 3-dioxygenase (IDO) during murine pregnancy is required to prevent rejection of the allogeneic fetus by maternal T cells. In addition to their role in pregnancy, IDO-expressing cells are widely distributed in primary and secondary lymphoid organs. Here we show that monocytes that have differentiated under the influence of macrophage colony-stimulating factor acquire the ability to suppress T cell proliferation in vitro via rapid and selective degradation of tryptophan by IDO. IDO was induced in macrophages by a synergistic combination of the T cell-derived signals IFN-gamma and CD40-ligand. Inhibition of IDO with the 1-methyl analogue of tryptophan prevented macrophage-mediated suppression. Purified T cells activated under tryptophan-deficient conditions were able to synthesize protein, enter the cell cycle, and progress normally through the initial stages of G1, including upregulation of IL-2 receptor and synthesis of IL-2. However, in the absence of tryptophan, cell cycle progression halted at a mid-G1 arrest point. Restoration of tryptophan to arrested cells was not sufficient to allow further cell cycle progression nor was costimulation via CD28. T cells could exit the arrested state only if a second round of T cell receptor signaling was provided in the presence of tryptophan. These data reveal a novel mechanism by which antigen-presenting cells can regulate T cell activation via tryptophan catabolism. We speculate that expression of IDO by certain antigen presenting cells in vivo allows them to suppress unwanted T cell responses.
Assuntos
Macrófagos/metabolismo , Linfócitos T/citologia , Triptofano Oxigenase/metabolismo , Triptofano/análogos & derivados , Ciclo Celular , Divisão Celular , Células Cultivadas , Técnicas de Cocultura , Meios de Cultura , DNA/biossíntese , Fase G1 , Expressão Gênica , Humanos , Indolamina-Pirrol 2,3,-Dioxigenase , Ativação Linfocitária , Fator Estimulador de Colônias de Macrófagos/farmacologia , Macrófagos/efeitos dos fármacos , Linfócitos T/metabolismo , Triptofano/metabolismo , Triptofano/farmacologia , Triptofano Oxigenase/genéticaRESUMO
In 1953 Medawar pointed out that survival of the genetically disparate (allogeneic) mammalian conceptus contradicts the laws of tissue transplantation. Rapid T cell-induced rejection of all allogeneic concepti occurred when pregnant mice were treated with a pharmacologic inhibitor of indoleamine 2,3-dioxygenase (IDO), a tryptophan-catabolizing enzyme expressed by trophoblasts and macrophages. Thus, by catabolizing tryptophan, the mammalian conceptus suppresses T cell activity and defends itself against rejection.
Assuntos
Feto/imunologia , Tolerância Imunológica , Linfócitos T/imunologia , Trofoblastos/enzimologia , Triptofano Oxigenase/metabolismo , Triptofano/metabolismo , Animais , Inibidores Enzimáticos/farmacologia , Feminino , Genes MHC Classe I , Genes RAG-1 , Antígenos H-2/genética , Humanos , Indolamina-Pirrol 2,3,-Dioxigenase , Fator Estimulador de Colônias de Macrófagos/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Placenta/enzimologia , Gravidez , Linfócitos T/metabolismo , Transgenes , Triptofano/análogos & derivados , Triptofano/farmacologia , Triptofano Oxigenase/antagonistas & inibidoresRESUMO
Monocyte-derived macrophages (Mphis) are pivotal participants in the pathogenesis of atherosclerosis. Evidence from both animal and human plaques indicates that local proliferation may contribute to accumulation of lesion Mphis, and the major Mphi growth factor, macrophage colony stimulating factor (MCSF), is present in atherosclerotic plaques. However, most in vitro studies have failed to demonstrate that human monocytes/Mphis possess significant proliferative capacity. We now report that, although human monocytes cultured in isolation showed only limited MCSF-induced proliferation, monocytes cocultured with aortic endothelial cells at identical MCSF concentrations underwent enhanced (up to 40-fold) and prolonged (21 d) proliferation. In contrast with monocytes in isolation, this was optimal at low seeding densities, required endothelial cell contact, and could not be reproduced by coculture with smooth muscle cells. Intimal Mphi isolated from human aortas likewise showed endothelial cell contact-dependent, MCSF-induced proliferation. Consistent with a two-signal mechanism governing Mphi proliferation, the cell cycle regulatory protein, cyclin E, was rapidly upregulated by endothelial cell contact in an MCSFindependent fashion, but MCSF was required for successful downregulation of the cell cycle inhibitory protein p27(Kip1) before cell cycling. Thus endothelial cells and MCSF differentially and synergistically regulate two Mphi genes critical for progression through the cell cycle.
Assuntos
Divisão Celular , Endotélio Vascular/fisiologia , Fator Estimulador de Colônias de Macrófagos/fisiologia , Macrófagos/citologia , Monócitos/citologia , Adolescente , Adulto , Aorta , Agregação Celular , Células Cultivadas , Técnicas de Cocultura , DNA/biossíntese , Endotélio Vascular/metabolismo , Feminino , Humanos , Fator Estimulador de Colônias de Macrófagos/biossíntese , Fator Estimulador de Colônias de Macrófagos/genética , Masculino , Microscopia Eletrônica , Pessoa de Meia-Idade , RNA Mensageiro/análiseRESUMO
In this study we continue our examination of the unique form of antibody-dependent antitumor cytotoxicity (ADCC) which develops when human monocytes are exposed to macrophage colony-stimulating factor (MCSF) in vitro. This form of ADCC is not present in fresh monocytes and emerges only as monocytes differentiate into monocyte-derived macrophages (MDM). We now report that the presence of gamma-interferon (IFN-gamma) during this period of differentiation markedly affects the development of MCSF-induced cytotoxicity. The addition of IFN-gamma on day 0 resulted in a pronounced dose-dependent inhibition of ADCC measured on day 7 (mean inhibition, 76 +/- 12%; range, 66-94%). MDM exposed to MCSF plus IFN-gamma required 3-10-fold higher effector to target cell ratios to achieve a level of cytotoxicity comparable to that of MDM cultured with MCSF alone. This inhibitory effect was attributable to an IFN-gamma-induced shift in the basic mechanism of target cell killing, away from the phagocytic form normally seen with MCSF and toward a significantly less effective extracellular form. In order to influence ADCC, IFN-gamma had to be present prior to the onset of differentiation; if it was added later it had progressively less effect, and if it was added after differentiation was complete it was inactive. The modulatory effects of IFN-gamma also extended to a number of other developmentally regulated attributes. MDM cultured with MCSF normally acquired a characteristic morphology and immunophenotype, re-entered the cell cycle, and changed functionally from accessory cells for mitogen-induced lymphocyte activation to suppressor cells. The presence of IFN-gamma prevented the emergence of each of these attributes. Despite these negative effects, MDM exposed to IFN-gamma remained viable, continued to bind and internalize MCSF, and displayed superior accessory cell function and oxidative burst activity. Taken together, our findings suggest that human monocytes are capable of following at least two distinct differentiation pathways in response to the local cytokine environment, with significant impact on the resultant macrophage phenotype in general and antitumor cytotoxicity in particular.
Assuntos
Citotoxicidade Celular Dependente de Anticorpos/efeitos dos fármacos , Interferon gama/farmacologia , Fator Estimulador de Colônias de Macrófagos/farmacologia , Monócitos/efeitos dos fármacos , Citotoxicidade Celular Dependente de Anticorpos/imunologia , Diferenciação Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Humanos , Imunofenotipagem , Ativação Linfocitária/efeitos dos fármacos , Ativação de Macrófagos/efeitos dos fármacos , Macrófagos/efeitos dos fármacos , Macrófagos/imunologia , Macrófagos/metabolismo , Monócitos/citologia , Monócitos/imunologia , Nitroazul de Tetrazólio/metabolismo , Oxirredução , Fenótipo , Espécies Reativas de Oxigênio/metabolismo , Receptor de Fator Estimulador de Colônias de Macrófagos/metabolismoRESUMO
Disialoganglioside GD2 is present on human neuroblastoma and melanoma cells. 3F8 is a murine IgG3 monoclonal antibody specific for GD2, which has shown antitumor effects in patients in preliminary clinical studies. Since antibody mediated cellular cytotoxicity (ADCC) was one of the likely mechanisms producing these observed tumor regressions, the current study was carried out to investigate the activation of ADCC by interleukin-2 (IL-2). ADCC (against human neuroblastoma and melanoma cell lines in vitro) mediated by normal human peripheral blood lymphocytes was increased 100 to 330% after preincubation with IL-2. At limiting concentrations of 3F8 antibody (10 to 100 times less than the amount required by unactivated peripheral blood lymphocytes), activated peripheral blood lymphocytes still mediated efficient ADCC. Activation of ADCC was detected earlier than lymphokine activated killer cell (LAK) activity, required less IL-2 for optimum induction (50 versus 1000 units/ml), and was of equal or greater absolute magnitude (+10 to +200%) against the cell lines tested. ADCC and LAK were independent and additive when measured against the same cell line. The precursor cells for both LAK and activated ADCC bore IgG Fc receptors, but by day 4 of culture with IL-2 much of the LAK activity resided in the Fc negative, Leu11 negative population, and did not mediate ADCC. IL-2 activated ADCC may be of value alone or in conjunction with LAK cells in the therapy of tumors which bind the antibody 3F8.
Assuntos
Citotoxicidade Celular Dependente de Anticorpos/efeitos dos fármacos , Interleucina-2/farmacologia , Melanoma/imunologia , Células Tumorais Cultivadas/efeitos dos fármacos , Anticorpos Monoclonais , Complexo Antígeno-Anticorpo/metabolismo , Proteínas do Sistema Complemento/imunologia , Humanos , Células Matadoras Naturais/efeitos dos fármacos , Células Matadoras Naturais/imunologia , Leucemia Eritroblástica Aguda/imunologia , Leucemia Eritroblástica Aguda/patologia , Melanoma/patologia , Neuroblastoma/imunologia , Neuroblastoma/patologia , Células Tumorais Cultivadas/imunologiaRESUMO
Human monocyte-derived macrophages (MDM) mediate efficient antibody-dependent cellular cytotoxicity (ADCC) against a variety of human tumor cell types in the presence of an anti-tumor monoclonal antibody. We have recently shown that the mechanism of this ADCC in our in vitro system involves phagocytosis of intact tumor cells. Some forms of macrophage ADCC have been reported to be inhibited by serum immunoglobulin, which competes with monoclonal antibodies for binding to the high-affinity Fc receptor (FcRI). In this study we investigated the role of the three macrophage FcR-gamma in antibody-dependent tumor cell phagocytosis. Hybridoma cells bearing surface antibody directed against either of the two low-affinity Fc receptors (FcRII or FcRIII) were efficiently phagocytosed by MDM, compared to hybridomas bearing irrelevant antibody. Soluble anti-receptor antibodies against FcRII and FcRIII were able to inhibit ADCC but only when both antibodies were simultaneously present. These data suggest that either low-affinity Fc receptor is capable of functioning independently to mediate phagocytosis of tumor cells. Consistent with a mechanism involving the low-affinity receptors rather than FcRI, antibody-dependent phagocytosis occurred in the presence of human serum, purified human IgG, and irrelevant murine antibody. Greater than 75% of the MDM in our culture system were able to ingest tumor cells when a suitable target was available. Optimal phagocytosis occurred at monoclonal antibody concentrations of 10-100 ng/ml. Like other forms of macrophage phagocytosis, ingestion of tumor cells required the presence of divalent cations (either Ca2+ or Mg2+) and an intact actin cytoskeleton (as indicated by sensitivity to cytochalasin D). Because FcRI is normally occupied in vivo by serum immunoglobulin, the participation of low-affinity FcR in tumor cell phagocytosis is potentially important in establishing the in vivo applicability of this efficient form of cytotoxicity.
Assuntos
Citotoxicidade Celular Dependente de Anticorpos/fisiologia , Macrófagos/fisiologia , Neoplasias/fisiopatologia , Fagocitose/imunologia , Receptores Fc/fisiologia , Animais , Citotoxicidade Celular Dependente de Anticorpos/efeitos dos fármacos , Antígenos de Diferenciação/biossíntese , Antígenos de Diferenciação/fisiologia , Cálcio/farmacologia , Linhagem Celular , Citocalasinas/farmacologia , Ácido Edético/farmacologia , Citometria de Fluxo , Imunofluorescência , Humanos , Hibridomas , Camundongos , Receptores Fc/biossíntese , Receptores de IgGRESUMO
In a Phase II study, 14 patients with metastatic gastrointestinal cancer received the mAb D612 (40 mg/m2, days 4, 7, and 11) in combination with recombinant human monocyte colony-stimulating factor [(rhM-CSF) 80 micrograms/kg/days 1-14]. The combined treatment was well tolerated and resulted in characteristic biological activity associated with each of the agents. Thus, 10 of 14 patients experienced D612-associated secretory diarrhea, which responded to the prostaglandin inhibitor Indomethacin in 5 of 7 patients. rhM-CSF therapy was associated with peripheral monocytosis (peak absolute monocyte count, 1444 +/- 394/mm3) and thrombocytopenia (nadir count, 78 +/- 10/mm3). Monocyte surface marker analysis revealed a high baseline expression of CD16+ cells in our patient population with an additional increase with rhM-CSF therapy. We observed a correlation between the degree of thrombocytopenia and the pretreatment CD16+ monocyte count. Of the plasma cytokines assayed, serum Neopterin demonstrated the most consistent increase during rhM-CSF therapy. There was a significant difference in the half-life of the first and last dose of D612 (35.8 +/- 2 versus 27 +/- 2.9 h; P < 0.05). Eleven of fourteen patients developed low-moderate levels of anti-D612 antibody. Despite the observed biological activity of both rhM-CSF and D612 and the previously described in vitro synergy, no clinical antitumor responses were observed in this Phase II study.
Assuntos
Anticorpos Monoclonais/administração & dosagem , Neoplasias Gastrointestinais/terapia , Fator Estimulador de Colônias de Macrófagos/administração & dosagem , Adulto , Idoso , Animais , Anticorpos Anti-Idiotípicos/sangue , Anticorpos Monoclonais/efeitos adversos , Anticorpos Monoclonais/farmacocinética , Contagem de Células Sanguíneas , Citocinas/sangue , Feminino , Humanos , Fator Estimulador de Colônias de Macrófagos/efeitos adversos , Masculino , Camundongos , Pessoa de Meia-Idade , Metástase Neoplásica , Receptores de IgG/análise , Proteínas Recombinantes/administração & dosagemRESUMO
Composition of the gut microbiota has profound effects on intestinal carcinogenesis. Diet and host genetics play critical roles in shaping the composition of gut microbiota. Whether diet and host genes interact with each other to bring specific changes in gut microbiota that affect intestinal carcinogenesis is unknown. Ability of dietary fibre to specifically increase beneficial gut microbiota at the expense of pathogenic bacteria in vivo via unknown mechanism is an important process that suppresses intestinal inflammation and carcinogenesis. Free fatty acid receptor 2 (FFAR2 or GPR43) is a receptor for short-chain fatty acids (acetate, propionate and butyrate), metabolites of dietary fibre fermentation by gut microbiota. Here, we show FFAR2 is down modulated in human colon cancers than matched adjacent healthy tissue. Consistent with this, Ffar2(-/-) mice are hypersusceptible to development of intestinal carcinogenesis. Dietary fibre suppressed colon carcinogenesis in an Ffar2-dependent manner. Ffar2 played an essential role in dietary fibre-mediated promotion of beneficial gut microbiota, Bifidobacterium species (spp) and suppression of Helicobacter hepaticus and Prevotellaceae. Moreover, numbers of Bifidobacterium is reduced, whereas those of Prevotellaceae are increased in human colon cancers than matched adjacent normal tissue. Administration of Bifidobacterium mitigated intestinal inflammation and carcinogenesis in Ffar2(-/-) mice. Taken together, these findings suggest that interplay between dietary fibre and Ffar2 play a key role in promoting healthy composition of gut microbiota that stimulates intestinal health.
RESUMO
The mechanisms of induction and maintenance of tolerance in self-reactive T cells in the periphery are poorly understood. Current models assume that successful T cell activation only occurs if ligation of the T cell receptor (signal 1) by antigen presenting cells (APCs) is accompanied by a costimulatory signal (signal 2), and that signal 1 in the absence of signal 2 is either ignored or is tolerizing. However, there is also evidence for the existence of macrophages (M phi) capable of suppressing T cell activation both in vitro and in vivo. The possibility of a more actively induced tolerance exists, in which the M phi itself responds to T cell-mediated signals in a tolerogenic fashion. This would help to resolve the paradox that tissue M phi, which act as scavengers of self-antigen, can also act as professional APCs. The ability of tissue macrophages to actively suppress T cells would further underscore the importance of the innate immune system in regulating adaptive immune responses.
Assuntos
Comunicação Celular/imunologia , Tolerância Imunológica , Macrófagos/imunologia , Linfócitos T/imunologia , Animais , Humanos , Ativação LinfocitáriaRESUMO
The murine conceptus is protected from maternal immunity by cells expressing indoleamine dioxygenase (IDO), which catabolizes tryptophan. Induction of lethal maternal anti-fetal immunity requires effective pharmacologic inhibition of IDO enzyme activity and the presence of maternal T cells, but not B cells and also depends on the degree of maternal-fetal tissue incompatibility. Based on these findings, we propose a model to explain the role of IDO in suppressing maternal immunity and the mechanism of fetal allograft rejection, when IDO activity is inhibited during gestation. This model incorporates observations that fetal allograft rejection is T cell dependent, antibody-independent and is accompanied by a novel type of inflammation involving extensive complement deposition at the maternal-fetal interface, when IDO activity is blocked during murine pregnancy.
Assuntos
Complicações na Gravidez/imunologia , Linfócitos T/imunologia , Triptofano/metabolismo , Animais , Proteínas do Sistema Complemento/imunologia , Modelos Animais de Doenças , Feminino , Humanos , Indolamina-Pirrol 2,3,-Dioxigenase , Troca Materno-Fetal/imunologia , Gravidez , Resultado da Gravidez , Triptofano Oxigenase/antagonistas & inibidores , Triptofano Oxigenase/fisiologiaRESUMO
The IDO pathway is implicated in a number of settings which lead to acquired peripheral tolerance. One such setting may be the functional tolerance displayed by tumor-bearing hosts toward tumor-associated antigens. Foxp3(+) Tregs are now recognized as a major contributor to tumor-induced immune suppression and functional tolerance. Emerging evidence links the IDO pathway with Treg biology at several points. The first is the ability of IDO-expressing DCs to drive the differentiation of naive CD4(+) T cells toward a Foxp3+ (inducible Treg) phenotype. The second link is the ability of IDO-expressing DCs to directly activate mature, pre-existing Tregs for markedly enhanced suppression of target cells. And the third link is the ability of IDO to prevent the inflammation-induced conversion ("reprogramming") of Tregs into pro-inflammatory T-helper-like cells in vivo. Taken together, these findings suggest that IDO may represent an important regulatory checkpoint influencing Treg activity: both by stabilizing and augmenting the suppressive phenotype, and by preventing Treg reprogramming into non-suppressive helper-like cells.
Assuntos
Indolamina-Pirrol 2,3,-Dioxigenase/imunologia , Neoplasias/enzimologia , Neoplasias/imunologia , Linfócitos T Reguladores/imunologia , Animais , Inibidores Enzimáticos/farmacologia , Fatores de Transcrição Forkhead/imunologia , Humanos , Tolerância Imunológica , Indolamina-Pirrol 2,3,-Dioxigenase/antagonistas & inibidores , Interleucina-6/imunologia , Cinurenina/imunologia , Proteínas Serina-Treonina Quinases/imunologia , Linfócitos T Reguladores/enzimologiaAssuntos
Fator Estimulador de Colônias de Macrófagos/uso terapêutico , Animais , Hematopoese/efeitos dos fármacos , Humanos , Fator Estimulador de Colônias de Macrófagos/metabolismo , Fator Estimulador de Colônias de Macrófagos/farmacologia , Neoplasias/terapia , Neutropenia/terapia , Receptor de Fator Estimulador de Colônias de Macrófagos/análiseRESUMO
Agents that interfere with tumoral immune tolerance may be useful to prevent or treat cancer. Brassinin is a phytoalexin, a class of natural products derived from plants that includes the widely known compound resveratrol. Brassinin has been demonstrated to have chemopreventive activity in preclinical models but the mechanisms underlying its anticancer properties are unknown. Here, we show that brassinin and a synthetic derivative 5-bromo-brassinin (5-Br-brassinin) are bioavailable inhibitors of indoleamine 2,3-dioxygenase (IDO), a pro-toleragenic enzyme that drives immune escape in cancer. Like other known IDO inhibitors, both of these compounds combined with chemotherapy to elicit regression of autochthonous mammary gland tumors in MMTV-Neu mice. Furthermore, growth of highly aggressive melanoma isograft tumors was suppressed by single agent treatment with 5-Br-brassinin. This response to treatment was lost in athymic mice, indicating a requirement for active host T-cell immunity, and in IDO-null knockout mice, providing direct genetic evidence that IDO inhibition is essential to the antitumor mechanism of action of 5-Br-brassinin. The natural product brassinin thus provides the structural basis for a new class of compounds with in vivo anticancer activity that is mediated through the inhibition of IDO.
Assuntos
Antineoplásicos/farmacologia , Indolamina-Pirrol 2,3,-Dioxigenase/antagonistas & inibidores , Indóis/farmacologia , Neoplasias Mamárias Experimentais/tratamento farmacológico , Melanoma Experimental/tratamento farmacológico , Tiocarbamatos/farmacologia , Animais , Células COS , Chlorocebus aethiops , Indolamina-Pirrol 2,3,-Dioxigenase/química , Neoplasias Mamárias Experimentais/enzimologia , Melanoma Experimental/enzimologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Nus , Camundongos Transgênicos , Relação Estrutura-AtividadeRESUMO
Human monocytes exposed in vitro to recombinant macrophage-colony-stimulating factor (rhMCSF) differentiate into monocyte-derived macrophages (MDM), which mediate efficient antibody-dependent cytotoxicity (ADCC) against tumor cells. We and others have shown that this form of ADCC is unusual in that phagocytosis, rather than extracellular lysis, appears to play the major role in target cell killing. In this study, we asked whether the phagocytic form of cytotoxicity seen with ADCC could occur in the absence of an opsonizing antibody. We now report that, whereas cell lines derived from solid tumors are often resistant to antibody-independent cytotoxicity, malignant cells of lymphoid origin appear particularly susceptible to such antibody-independent killing. We found that all of nine lymphocytic leukemia and lymphoma cell lines tested in a total of 35 experiments, plus all four samples of fresh leukemic blasts, were consistently susceptible to antibody-independent MDM cytotoxicity. Antibody-independent cytotoxicity against these cells was efficient (40%-63% killing) at effector: target (E:T) ratios as low as 2:1. Like ADCC, antibody-independent cytotoxicity involved phagocytosis of target cells, as demonstrated by ingestion of fluorescently labeled targets and analysis by flow cytometry. At the time of phagocytosis, the majority of target cells retained membrane integrity, as indicated by the direct transfer of intracellular [51Cr]chromate from radiolabeled targets to phagocytosing MDM, without release of the label into the medium. However, in contrast to ADCC, we found that the degree of antibody-independent cytotoxicity was not a function of the E:T ratio. Instead, a constant proportion of the available target cells were killed regardless of the E:T ratio, suggesting that target cell recognition, rather than effector cell potency, might be the limiting factor in determining cytotoxicity. In additional experiments, we have also identified a second tumor cell type, nueroblastoma, as being susceptible to antibody-independent phagocytosis (all of five cell lines tested, cytotoxicity 40%-93%, E:T = 3:1). Our data thus indicate that the cytotoxicity induced by rhMCSF is not confined to antibody-mediated killing, and that phagocytosis can play a significant role in target cell destruction even in the absence of opsonizing antibody.
Assuntos
Fator Estimulador de Colônias de Macrófagos/farmacologia , Macrófagos/citologia , Fagocitose/efeitos dos fármacos , Leucemia-Linfoma Linfoblástico de Células Precursoras/imunologia , Humanos , Imunidade Celular , Técnicas In Vitro , Monócitos/citologia , Leucemia-Linfoma Linfoblástico de Células Precursoras/patologia , Proteínas Recombinantes , Células Tumorais CultivadasRESUMO
Mammals owe their existence to immunosuppressive processes that prevent fetal rejection in utero. Blocking tryptophan catabolism during murine pregnancy allows maternal T cells to provoke fetal allograft rejection. Cells expressing indoleamine 2,3-dioxygenase (IDO), which catabolizes tryptophan, prevent T cell cycle progression and enhance activation induced T cell death. Here, we discuss the role of cells expressing IDO in regulating maternal T cell immunity during pregnancy and consider whether this mechanism might contribute to immunological discrimination by promoting T cell tolerance in other circumstances.
Assuntos
Tolerância Imunológica , Gravidez/imunologia , Animais , Células Apresentadoras de Antígenos/imunologia , Morte Celular , Feminino , Humanos , Indolamina-Pirrol 2,3,-Dioxigenase , Ativação Linfocitária , Troca Materno-Fetal/imunologia , Camundongos , Gravidez/metabolismo , Linfócitos T/imunologia , Linfócitos T/metabolismo , Triptofano/imunologia , Triptofano/metabolismo , Triptofano Oxigenase/metabolismoRESUMO
Some macrophages inhibit microbial infections by producing indoleamine 2,3 dioxygenase (IDO), which catabolizes tryptophan. Here, Andrew Mellor and David Munn discuss evidence that cells that synthesize IDO protect the mammalian fetus from maternal T-cell attack and argue that this mechanism might have wider implications for the control of T-cell responses.