RESUMO
Currently, we are experiencing a true pandemic of a communicable disease by the virus SARS-CoV-2 holding the whole world firmly in its grasp. Amazingly and unfortunately, this virus uses a metabolic and endocrine pathway via ACE2 to enter our cells causing damage and disease. Our international research training programme funded by the German Research Foundation has a clear mission to train the best students wherever they may come from to learn to tackle the enormous challenges of diabetes and its complications for our society. A modern training programme in diabetes and metabolism does not only involve a thorough understanding of classical physiology, biology and clinical diabetology but has to bring together an interdisciplinary team. With the arrival of the coronavirus pandemic, this prestigious and unique metabolic training programme is facing new challenges but also new opportunities. The consortium of the training programme has recognized early on the need for a guidance and for practical recommendations to cope with the COVID-19 pandemic for the community of patients with metabolic disease, obesity and diabetes. This involves the optimal management from surgical obesity programmes to medications and insulin replacement. We also established a global registry analyzing the dimension and role of metabolic disease including new onset diabetes potentially triggered by the virus. We have involved experts of infectious disease and virology to our faculty with this metabolic training programme to offer the full breadth and scope of expertise needed to meet these scientific challenges. We have all learned that this pandemic does not respect or heed any national borders and that we have to work together as a global community. We believe that this transCampus metabolic training programme provides a prime example how an international team of established experts in the field of metabolism can work together with students from all over the world to address a new pandemic.
Assuntos
COVID-19 , Diabetes Mellitus , Educação Médica Continuada , Obesidade , Pandemias , SARS-CoV-2 , COVID-19/epidemiologia , COVID-19/terapia , Diabetes Mellitus/epidemiologia , Diabetes Mellitus/terapia , Humanos , Obesidade/epidemiologia , Obesidade/terapiaRESUMO
Understanding the evolution of the direct and indirect pathways of allorecognition following tissue transplantation is essential in the design of tolerance-promoting protocols. On the basis that donor bone marrow-derived antigen-presenting cells are eliminated within days of transplantation, it has been argued that the indirect response represents the major threat to long-term transplant survival, and is consequently the key target for regulation. However, the detection of MHC transfer between cells, and particularly the capture of MHC:peptide complexes by dendritic cells (DCs), led us to propose a third, semidirect, pathway of MHC allorecognition. Persistence of this pathway would lead to sustained activation of direct-pathway T cells, arguably persisting for the life of the transplant. In this study, we focused on the contribution of acquired MHC-class I on recipient DCs during the life span of a skin graft. We observed that MHC-class I acquisition by recipient DCs occurs for at least 1 month following transplantation and may be the main source of alloantigen that drives CD8+ cytotoxic T cell responses. In addition, acquired MHC-class I:peptide complexes stimulate T cell responses in vivo, further emphasizing the need to regulate both pathways to induce indefinite survival of the graft.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Células Dendríticas/imunologia , Rejeição de Enxerto/imunologia , Imunidade Celular/imunologia , Isoantígenos/imunologia , Fragmentos de Peptídeos/imunologia , Transplante de Pele/efeitos adversos , Aloenxertos , Animais , Apresentação de Antígeno/imunologia , Rejeição de Enxerto/patologia , Tolerância Imunológica/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Doadores de Tecidos , TransplantadosRESUMO
Regulatory T cell (Treg) therapy using recipient-derived Tregs expanded ex vivo is currently being investigated clinically by us and others as a means of reducing allograft rejection following organ transplantation. Data from animal models has demonstrated that adoptive transfer of allospecific Tregs offers greater protection from graft rejection compared to polyclonal Tregs. Chimeric antigen receptors (CAR) are clinically translatable synthetic fusion proteins that can redirect the specificity of T cells toward designated antigens. We used CAR technology to redirect human polyclonal Tregs toward donor-MHC class I molecules, which are ubiquitously expressed in allografts. Two novel HLA-A2-specific CARs were engineered: one comprising a CD28-CD3ζ signaling domain (CAR) and one lacking an intracellular signaling domain (ΔCAR). CAR Tregs were specifically activated and significantly more suppressive than polyclonal or ΔCAR Tregs in the presence of HLA-A2, without eliciting cytotoxic activity. Furthermore, CAR and ΔCAR Tregs preferentially transmigrated across HLA-A2-expressing endothelial cell monolayers. In a human skin xenograft transplant model, adoptive transfer of CAR Tregs alleviated the alloimmune-mediated skin injury caused by transferring allogeneic peripheral blood mononuclear cells more effectively than polyclonal Tregs. Our results demonstrated that the use of CAR technology is a clinically applicable refinement of Treg therapy for organ transplantation.
Assuntos
Rejeição de Enxerto/prevenção & controle , Antígeno HLA-A2/imunologia , Receptores de Antígenos/imunologia , Transplante de Pele/efeitos adversos , Linfócitos T Reguladores/imunologia , Aloenxertos , Animais , Rejeição de Enxerto/etiologia , Sobrevivência de Enxerto/imunologia , Xenoenxertos , Humanos , Leucócitos Mononucleares , Camundongos , Camundongos Endogâmicos BALB C , Tolerância ao Transplante/imunologiaRESUMO
The concept of regulatory T cell (Treg ) therapy in transplantation is now a reality. Significant advances in science and technology have enabled us to isolate human Tregs , expand them to clinically relevant numbers and infuse them into human transplant recipients. With several Phase I/II trials under way investigating Treg safety and efficacy it is now more crucial than ever to understand their complex biology. However, our journey is by no means complete; results from these trials will undoubtedly provoke both further knowledge and enquiry which, alongside evolving science, will continue to drive the optimization of Treg therapy in the pursuit of transplantation tolerance. In this review we will summarize current knowledge of Treg biology, explore novel technologies in the setting of Treg immunotherapy and address key prerequisites surrounding the clinical application of Tregs in transplantation.
Assuntos
Imunidade Adaptativa , Rejeição de Enxerto/tratamento farmacológico , Imunoterapia/métodos , Transplante de Órgãos , Linfócitos T Reguladores/imunologia , Tolerância ao Transplante , Animais , Ensaios Clínicos como Assunto , Criopreservação , Humanos , Imunossupressores/uso terapêutico , CamundongosRESUMO
Anti-apoptotic genes, including those of the Bcl-2 family, have been shown to have dual functionality inasmuch as they inhibit cell death but also regulate inflammation. Several anti-apoptotic molecules have been associated with endothelial cell (EC) survival following transplantation; however, their exact role has yet to be elucidated in respect to controlling inflammation. In this study we created mice expressing murine A1 (Bfl-1), a Bcl-2 family member, under the control of the human intercellular adhesion molecule 2 (ICAM-2) promoter. Constitutive expression of A1 in murine vascular ECs conferred protection from cell death induced by the proinflammatory cytokine tumour necrosis factor (TNF)-α. Importantly, in a mouse model of heart allograft transplantation, expression of A1 in vascular endothelium increased survival in the absence of CD8+ T cells. Better graft outcome in mice receiving an A1 transgenic heart correlated with a reduced immune infiltration, which may be related to increased EC survival and reduced expression of adhesion molecules on ECs. In conclusion, constitutive expression of the anti-apoptotic molecule Bfl1 (A1) in murine vascular ECs leads to prolonged allograft survival due to modifying inflammation.
Assuntos
Células Endoteliais/metabolismo , Expressão Gênica , Transplante de Coração , Antígenos de Histocompatibilidade Menor/genética , Proteínas Proto-Oncogênicas c-bcl-2/genética , Tolerância ao Transplante , Animais , Antígenos CD/genética , Apoptose , Linfócitos T CD8-Positivos , Moléculas de Adesão Celular/genética , Modelos Animais de Doenças , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/imunologia , Endotélio Vascular/citologia , Sobrevivência de Enxerto , Humanos , Inflamação , Camundongos , Regiões Promotoras Genéticas , Transplante Homólogo , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
We and others have previously described signatures of tolerance in kidney transplantation showing the differential expression of B cell-related genes and the relative expansions of B cell subsets. However, in all of these studies, the index group-namely, the tolerant recipients-were not receiving immunosuppression (IS) treatment, unlike the rest of the comparator groups. We aimed to assess the confounding effect of these regimens and develop a novel IS-independent signature of tolerance. Analyzing gene expression in three independent kidney transplant patient cohorts (232 recipients and 14 tolerant patients), we have established that the expression of the previously reported signature was biased by IS regimens, which also influenced transitional B cells. We have defined and validated a new gene expression signature that is independent of drug effects and also differentiates tolerant patients from healthy controls (cross-validated area under the receiver operating characteristic curve [AUC] = 0.81). In a prospective cohort, we have demonstrated that the new signature remained stable before and after steroid withdrawal. In addition, we report on a validated and highly accurate gene expression signature that can be reliably used to identify patients suitable for IS reduction (approximately 12% of stable patients), irrespective of the IS drugs they are receiving. Only a similar approach will make the conduct of pilot clinical trials for IS minimization safe and hence allow critical improvements in kidney posttransplant management.
Assuntos
Biomarcadores/metabolismo , Rejeição de Enxerto/diagnóstico , Sobrevivência de Enxerto/imunologia , Tolerância Imunológica/imunologia , Imunossupressores/uso terapêutico , Transplante de Rim/efeitos adversos , Adulto , Idoso , Linfócitos B/efeitos dos fármacos , Linfócitos B/imunologia , Linfócitos B/metabolismo , Estudos de Casos e Controles , Feminino , Seguimentos , Taxa de Filtração Glomerular , Rejeição de Enxerto/tratamento farmacológico , Rejeição de Enxerto/etiologia , Rejeição de Enxerto/metabolismo , Sobrevivência de Enxerto/efeitos dos fármacos , Humanos , Tolerância Imunológica/efeitos dos fármacos , Falência Renal Crônica/complicações , Falência Renal Crônica/cirurgia , Testes de Função Renal , Masculino , Pessoa de Meia-Idade , Prognóstico , Estudos Prospectivos , Fatores de RiscoRESUMO
Regulatory T cell (Treg) therapy has the potential to induce transplantation tolerance so that immunosuppression and associated morbidity can be minimized. Alloantigen-reactive Tregs (arTregs) are more effective at preventing graft rejection than polyclonally expanded Tregs (PolyTregs) in murine models. We have developed a manufacturing process to expand human arTregs in short-term cultures using good manufacturing practice-compliant reagents. This process uses CD40L-activated allogeneic B cells to selectively expand arTregs followed by polyclonal restimulation to increase yield. Tregs expanded 100- to 1600-fold were highly alloantigen reactive and expressed the phenotype of stable Tregs. The alloantigen-expanded Tregs had a diverse TCR repertoire. They were more potent than PolyTregs in vitro and more effective at controlling allograft injuries in vivo in a humanized mouse model.
Assuntos
Terapia Baseada em Transplante de Células e Tecidos , Rejeição de Enxerto/prevenção & controle , Tolerância Imunológica/imunologia , Isoantígenos/imunologia , Transplante de Pele , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/transplante , Animais , Citometria de Fluxo , Rejeição de Enxerto/imunologia , Doença Enxerto-Hospedeiro/imunologia , Doença Enxerto-Hospedeiro/prevenção & controle , Humanos , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos BALB C , Tolerância ao TransplanteRESUMO
Transplantation is a successful treatment for end-stage organ failure. Despite improvements in short-term outcome, long-term survival remains suboptimal because of the morbidity and mortality associated with long-term use of immunosuppression. There is, therefore, a pressing need to devise protocols that induce tolerance in order to minimize or completely withdraw immunosuppression in transplant recipients. In this review we will discuss how regulatory T cells (T(regs)) came to be recognized as an attractive way to promote transplantation tolerance. We will summarize the preclinical data, supporting the importance of these cells in the induction and maintenance of immune tolerance and that provide the rationale for the isolation and expansion of these cells for cellular therapy. We will also describe the data from the first clinical trials, using T(regs) to inhibit graft-versus-host disease (GVHD) after haematopoietic stem cell transplantation and will address both the challenges and opportunities in human T(reg) cell therapy.
Assuntos
Transferência Adotiva , Terapia Baseada em Transplante de Células e Tecidos , Transplante de Células-Tronco Hematopoéticas , Linfócitos T Reguladores/transplante , Doença Enxerto-Hospedeiro/imunologia , Doença Enxerto-Hospedeiro/terapia , Humanos , Linfócitos T Reguladores/imunologia , Tolerância ao TransplanteRESUMO
Cell-based therapies using natural or genetically modified regulatory T cells (T(regs)) have shown significant promise as immune-based therapies. One of the main difficulties facing the further advancement of these therapies is that the fate and localization of adoptively transferred T(regs) is largely unknown. The ability to dissect the migratory pathway of these cells in a non-invasive manner is of vital importance for the further development of in-vivo cell-based immunotherapies, as this technology allows the fate of the therapeutically administered cell to be imaged in real time. In this review we will provide an overview of the current clinical imaging techniques used to track T cells and T(regs) in vivo, including magnetic resonance imaging (MRI) and positron emission tomography (PET)/single photon emission computed tomography (SPECT). In addition, we will discuss how the finding of these studies can be used, in the context of transplantation, to define the most appropriate T(reg) subset required for cellular therapy.
Assuntos
Transferência Adotiva , Imageamento por Ressonância Magnética , Tomografia por Emissão de Pósitrons , Linfócitos T Reguladores/fisiologia , Linfócitos T Reguladores/transplante , Tomografia Computadorizada de Emissão de Fóton Único , Animais , Linhagem Celular , Diagnóstico por Imagem , Humanos , Camundongos , Camundongos Endogâmicos C57BL , TransplanteRESUMO
To investigate the role of donor-specific indirect pathway T cells in renal transplant tolerance, we analyzed responses in peripheral blood of 45 patients using the trans-vivo delayed-type hypersensitivity assay. Subjects were enrolled into five groups-identical twin, clinically tolerant (TOL), steroid monotherapy (MONO), standard immunosuppression (SI) and chronic rejection (CR)-based on transplant type, posttransplant immunosuppression and graft function. The indirect pathway was active in all groups except twins but distinct intergroup differences were evident, corresponding to clinical status. The antidonor indirect pathway T effector response increased across patient groups (TOL < MONO < SI < CR; p < 0.0001) whereas antidonor indirect pathway T regulatory response decreased (TOL > MONO = SI > CR; p < 0.005). This pattern differed from that seen in circulating naïve B-cell numbers and in a cross-platform biomarker analysis, where patients on monotherapy were not ranked closest to TOL patients, but rather were indistinguishable from chronically rejecting patients. Cross-sectional analysis of the indirect pathway revealed a spectrum in T-regulatory:T-effector balance, ranging from TOL patients having predominantly regulatory responses to CR patients having predominantly effector responses. Therefore, the indirect pathway measurements reflect a distinct aspect of tolerance from the recently reported elevation of circulating naïve B cells, which was apparent only in recipients off immunosuppression.
Assuntos
Linfócitos B/imunologia , Rejeição de Enxerto/imunologia , Tolerância Imunológica/imunologia , Transplante de Rim/imunologia , Linfócitos T/imunologia , Doadores de Tecidos , Humanos , Terapia de Imunossupressão , Prognóstico , Transdução de SinaisRESUMO
Helicobacter pylori is one of the most common infections in the world. Despite inciting inflammation, immunological clearance of the pathogen is often incomplete. CD4(+) CD25(hi) forkhead box protein 3 (FoxP3(+)) regulatory T cells (T(regs)) are potent suppressors of different types of immune responses and have been implicated in limiting inflammatory responses to H. pylori. Investigating the influence of H. pylori on T(reg) function and proliferation, we found that H. pylori-stimulated dendritic cells (DCs) induced proliferation in T(regs) and impaired their suppressive capability. This effect was mediated by interleukin (IL)-1ß produced by H. pylori-stimulated DCs. These data correlated with in-vivo observations in which H. pylori(+) gastric mucosa contained more T(regs) in active cell division than uninfected stomachs. Inciting local proliferation of T(regs) and inhibiting their suppressive function may represent a mechanism for the chronic gastritis and carcinogenesis attributable to H. pylori.
Assuntos
Células Dendríticas/imunologia , Helicobacter pylori/imunologia , Interleucina-1beta/biossíntese , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/metabolismo , Mucosa Gástrica/imunologia , Mucosa Gástrica/metabolismo , Mucosa Gástrica/microbiologia , Infecções por Helicobacter/imunologia , Infecções por Helicobacter/metabolismo , Humanos , Interleucina-6/biossíntese , Ativação Linfocitária/imunologia , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismo , Linfócitos T Reguladores/citologia , Fatores de Tempo , Fator de Necrose Tumoral alfa/biossínteseRESUMO
CD4(+) CD25(+) regulatory T cells (T(reg) cells) are an attractive adoptive cell therapy in mediating transplantation tolerance. T-cell receptor (TcR) activation is critical for T(reg) function, suggesting that the TcR avidity of T(reg) cells used in therapy may affect the therapeutic outcome. To address this, we compared the regulatory capacity of T(reg) lines expressing TcRs derived from two TcR transgenic mice shown to have the same specificity but different functional avidities. T(reg) lines generated from CD4(+)CD25(+) T cells from C57BL/6 mice were transduced with one of either of these TcRs. The antigen specificity of the transduced T(reg) lines was confirmed in vitro. T(reg) lines expressing the TcR with higher functional avidity showed stronger suppressive capacity in a linked suppression model in vitro. Furthermore, the same T(reg) lines demonstrated a stronger proliferation in vivo following antigen exposure. Pretreatment of recipient BL/6 mice with these T(reg) cells, together with anti-CD8 antibody and Rapamycin therapies, prolonged survival of BALB/c skins, as compared with mice that received T(reg) lines with lower TcR avidity. Taken together, these data suggest that the TcR functional avidity may be important for T(reg) function. It highlights the fact that strategies to select T(reg) with higher functional avidity might be beneficial for immunotherapy in transplantation.
Assuntos
Linfócitos T Reguladores/imunologia , Animais , Sequência de Bases , Primers do DNA , Citometria de Fluxo , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos TransgênicosRESUMO
Successful expansion of functional CD4(+) CD25(+) regulatory T cells (T(reg)) ex vivo under good manufacturing practice conditions has made T(reg) -cell therapy in clinical transplant tolerance induction a feasible possibility. In animals, T(reg) cells home to both transplanted tissues and local lymph nodes and are optimally suppressive if active at both sites. Therefore, they have the opportunity to suppress both naïve and memory CD4(+) CD25(-) T cells (Tresp). Clinical transplantation commonly involves depleting therapy at induction (e.g. anti-CD25), which favors homeostatic expansion of memory T cells. Animal models suggest that T(reg) cells are less suppressive on memory, compared with naïve Tresp that mediate allograft rejection. As a result, in the context of human T(reg) -cell therapy, it is important to define the effectiveness of T(reg) cells in regulating naïve and memory Tresp. Therefore, we compared suppression of peripheral blood naïve and memory Tresp by fresh and ex vivo expanded T(reg) cells using proliferation, cytokine production and activation marker expression (CD154) as readouts. With all readouts, naïve human Tresp were more suppressible by approximately 30% than their memory counterparts. This suggests that T(reg) cells may be more efficacious if administered before or at the time of transplantation and that depleting therapy should be avoided in clinical trials of T(reg) cells.
Assuntos
Antígenos CD4/imunologia , Memória Imunológica , Subunidade alfa de Receptor de Interleucina-2/imunologia , Linfócitos T Reguladores/imunologia , Separação Celular , Células Cultivadas , Citometria de Fluxo , HumanosRESUMO
The immunogenicity of long-surviving, enhanced (AS X AUG)F1 renal allografts retransplanted into secondary AS recipients was restored by the injection of small numbers of donor strain dendritic cells derived from afferent lymph. Whereas 1 X 10(4) to 5 X 10(4) dendritic cells were able to trigger an acute rejection response, neither the passenger volume of donor strain blood nor 5 X 10(6) T or B lymphocytes were able to do so, thereby demonstrating more than a 100-fold difference in immunogenic potency. It is concluded that intrarenal dendritic cells provide the major immunogenic stimulus of a kidney allograft. These results suggest that the antigenic strength of major histocompatibility complex-incompatible tissue correlates with the content of donor strain dendritic cells. They also provide further evidence that antigens of the major histocompatibility complex behave like conventional antigens unless they are on the surface of allogeneic dendritic cells.
Assuntos
Dendritos/imunologia , Transplante de Rim , Leucócitos/imunologia , Animais , Formação de Anticorpos , Linfócitos B/imunologia , Adesão Celular , Sobrevivência de Enxerto , Rim/citologia , Ratos , Ratos Endogâmicos , Linfócitos T/imunologiaRESUMO
It has been previously shown that long surviving, enhanced (AS X AUG)F1 rat kidneys residing in a primary AS recipient are not acutely rejected if transferred into a second AS recipient. The reduced immunogenicity of the retransplanted graft was attributed to a depletion of incompatible passenger cells. It is shown here that if the primary AS recipient is made chimeric by x irradiation and injection of (AS X AUG)F1 bone marrow cells, transfer of the long surviving, enhanced graft into a second AS recipient provokes acute graft rejection comparable to that observed when normal (AS X AUG)F1 kidneys are transplanted into untreated AS recipients. Transplantation of passenger cell-depleted AUG kidneys into AS recipients leads to graft rejection, with a median survival time of 22 d. Treatment of these recipients with as little as 1.5 mg/kg cyclophosphamide for 14 d induces prolonged graft survival. By contrast, five times as much cyclophosphamide treatment is required to induce prolonged survival of normal AUG kidneys (i.e., containing incompatible passenger cells) transplanted to AS recipients. These results confirm that the major alloimmunogenic stimulus of rat kidney grafts is provided by the incompatible passenger cells.
Assuntos
Sobrevivência de Enxerto , Imunossupressores/farmacologia , Transplante de Rim , Quimera por Radiação , Animais , Células da Medula Óssea , Movimento Celular , Cruzamentos Genéticos , Ciclofosfamida/farmacologia , Relação Dose-Resposta Imunológica , Facilitação Imunológica de Enxerto , Ratos , Ratos Endogâmicos , Fatores de TempoRESUMO
The contributions of A alpha and A beta chains, and of subregions of A beta, to Ia-restricted recognition of antigen by Th lymphocytes were analyzed using a panel of L cells transfected with various pairs of A alpha b,d, or k genes and recombinant or wild-type A beta b,d, or k genes. The A beta genes included all possible exchanges of the whole NH2-terminal (beta 1) domain or halves of the beta 1 domain among these three allelic A beta genes. The Ia+ L cells derived from such transfections were used as antigen-presenting cells with a 21 member panel of responding Ia-restricted T hybridoma cells of differing nominal antigen specificity and Ia-restriction. Special care was taken to account for quantitative variation in levels of Ia expression throughout the experiments. The results of this analysis reveal that (a) only 2 of the 21 Th cells recognized Ia molecules involving either a nonparental A alpha or a nonparental A beta chain, and in both cases the degeneracy extended to only one of the two other alleles tested. This suggests that allele specific contributions from both A alpha and A beta chains are important in restricted recognition for most, if not all I-A-restricted Th cells. (b) In no case did substitution of the A beta 2 domain from either of the alternative haplotypes lead to any functionally detectable effects, demonstrating that polymorphisms in the A beta 1 domain can entirely account for the restriction imposed on Th cell responses by the entire A beta chain. (c) For 90% of the cells tested, replacement of the NH2-terminal portion of the beta 1 domain with an allogeneic segment led to Ia molecules unable to elicit Th responses. Furthermore, of all the cells permissive of the substitution of one or other half of the beta 1 domain, only two permitted the substitution of sequence from both alternative haplotypes. Taken together, these data strongly suggest that antigen recognition by most, if not all, I-A-restricted Th cells involves contributions from both halves of the A beta 1 domain. These data suggest that the role of I-A molecules in restricted Th cell recognition of antigen depends on conformational determinants unique to a particular combination of polymorphic alpha and beta chains, and that multiple such sites exist on a single Ia molecule.(ABSTRACT TRUNCATED AT 400 WORDS)
Assuntos
Antígenos de Histocompatibilidade Classe II/imunologia , Linfócitos T/imunologia , Animais , Células Apresentadoras de Antígenos/imunologia , DNA/genética , DNA Recombinante , Relação Dose-Resposta Imunológica , Epitopos , Genes , Genótipo , Hibridomas/imunologia , Células L , Camundongos , Polimorfismo Genético , Receptores de Antígenos de Linfócitos T/genética , Receptores de Antígenos de Linfócitos T/imunologia , TransfecçãoRESUMO
The ability of two HLA-DR-expressing human T cell clones to function as antigen-presenting cells (APC) was investigated using highly purified T cells. The results demonstrated that these T cell clones are unable to act as autonomous APC, and that recognition of nominal or alloantigens on the surface of T cells leads to a state of nonresponsiveness. The first observation was that a T cell clone with specificity for the 306-324 peptide of influenza hemagglutinin (HA), and raised from a DR1 responder, exhibited apparent degeneracy of major histocompatibility complex restriction when cultured with peptide in the presence of peripheral blood mononuclear cells (PBMC) expressing a wide variety of structurally unrelated DR types. However, when the PBMC were pulsed with peptide and washed before coculture with the clone, peptide was exclusively recognized with DR1Dw1. This implied that in the presence of soluble peptide the T cells were displaying ligand to each other, and that the third-party APC were providing costimulatory signals. To test the ability of T cells to act as autonomous APC, accessory cell-free preparations of two DR1-restricted clones were cultured with peptide in the presence or the absence of added B cell APC. T cell purity was established by the absence of proliferation in response to the mitogen phytohemagglutinin (PHA). PHA-nonresponsive T cells were completely unable to proliferate in response to peptide alone; furthermore, preculture of the HA-specific clone, in the complete absence of accessory cells, with the same concentration of peptide (1 microgram/ml) that induced optimal proliferation when presented by conventional APC, led to profound nonresponsiveness. The same phenomenon was also observed when two of three anti-DR1 alloreactive T cell clones were precultured with a DR1-expressing T cell clone. The ability of the DR1-expressing clone to induce nonresponsiveness in anti-DR1 clones correlated with recognition of the DR1 alloantigen on the DR1-expressing clone.
Assuntos
Células Apresentadoras de Antígenos/imunologia , Isoantígenos/imunologia , Linfócitos T/imunologia , Células Clonais , Antígenos HLA-DR/imunologia , Hemaglutininas Virais/imunologia , Humanos , Complexo Principal de Histocompatibilidade/imunologiaRESUMO
In situ hybridization was used to investigate the expression of T cell receptor (TCR) alpha, beta, and gamma mRNAs in developing fetal and adult precursor thymocytes. gamma transcription was observed at the earliest time tested (day 12), followed by beta 12 h later, and TCR alpha on day 16. The early beta transcripts appeared to be from unrearranged or incompletely rearranged (D-J-C) beta loci. V beta region transcription was first detectable on day 14 and transcription of different V beta genes was induced at different times. These results delineate a schedule sequence of TCR gene activation, which begins within 1 d after entry of stem cells into the fetal thymus.
Assuntos
Antígenos de Superfície/genética , Feto/imunologia , Hibridização de Ácido Nucleico , Receptores de Antígenos de Linfócitos T/genética , Linfócitos T/metabolismo , Animais , Feto/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , RNA Mensageiro/análise , Recombinação Genética , Antígenos Thy-1 , Timo/imunologia , Transcrição GênicaRESUMO
The role of endothelial cells (EC) in initiating a primary T cell response is of importance in clinical transplantation and autoimmunity since EC are the first allogeneic target encountered by the recipient's immune system and may display tissue-specific autoantigens in the context of an inflammatory response. In this study, we have investigated the antigen-presenting cell function of human umbilical vein-derived EC (HUVEC), depleted of constitutively major histocompatibility complex class II+ cells and induced to express class II molecules by interferon-gamma. The results show that HUVEC do not express B7 but can support proliferation by antigen-specific T cell clones. In contrast, they were unable to initiate a primary alloresponse using three independent HUVEC cultures and MHC class II-mismatched CD4+ T cells from eight donors. The response to HUVEC was reconstituted by trans-costimulation provided by DAP.3 transfectants expressing human B7.1. Coculture of peripheral blood T cells with EC expressing allogeneic DR molecules had markedly different effects on CD45RO+ and RA+ subsets. Subsequent reactivity of the RO+ T cells was unaffected by exposure to EC, indicating a neutral encounter. In contrast, culture with DR+ EC induced allospecific nonresponsiveness in RA+ T cells.
Assuntos
Apresentação de Antígeno , Endotélio Vascular/imunologia , Antígenos de Histocompatibilidade Classe II/imunologia , Tolerância Imunológica , Linfócitos T/imunologia , Antígenos CD/imunologia , Antígeno B7-2 , Técnicas de Cocultura , Endotélio Vascular/citologia , Humanos , Interferon gama/farmacologia , Glicoproteínas de Membrana/imunologia , Subpopulações de Linfócitos TRESUMO
The T cell response to major histocompatibility complex (MHC) alloantigens occurs via two main pathways. The direct pathway involves the recognition of intact allogeneic MHC:peptide complexes on donor cells and provokes uniquely high frequencies of responsive T cells. The indirect response results from alloantigens being processed like any other protein antigen and presented as peptide by autologous antigen-presenting cells. The frequencies of T cells with indirect allospecificity are orders of magnitude lower and comparable to other peptide-specific responses. In this study, we explored the contributions of naïve and memory CD4(+) T cells to these two pathways. Using an adoptive transfer and skin transplantation model we found that naive and memory CD4(+) T cells, both naturally occurring and induced by sensitization with multiple third-party alloantigens, contributed equally to graft rejection when only the direct pathway was operative. In contrast, the indirect response was predominantly mediated by the naïve subset. Elimination of regulatory CD4(+)CD25(+) T cells enabled memory cells to reject grafts through the indirect pathway, but at a much slower tempo than for naïve cells. These findings have implications for better targeting of immunosuppression to inhibit immediate and later forms of alloimmunity.