RESUMO
During acute graft-versus-host disease (aGVHD) in mice, autoreactive T cells can be generated de novo in the host thymus implying an impairment in self-tolerance induction. As a possible mechanism, we have previously reported that mature medullary thymic epithelial cells (mTEC(high)) expressing the autoimmune regulator are targets of donor T-cell alloimmunity during aGVHD. A decline in mTEC(high) cell pool size, which purges individual tissue-restricted peripheral self-antigens (TRA) from the total thymic ectopic TRA repertoire, weakens the platform for central tolerance induction. Here we provide evidence in a transgenic mouse system using ovalbumin (OVA) as a model surrogate TRA that the de novo production of OVA-specific CD4(+) T cells during acute GVHD is a direct consequence of impaired thymic ectopic OVA expression in mTEC(high) cells. Our data, therefore, indicate that a functional compromise of the medullary mTEC(high) compartment may link alloimmunity to the development of autoimmunity during chronic GVHD.
Assuntos
Autoimunidade , Linfócitos T CD4-Positivos/patologia , Doença Enxerto-Hospedeiro/patologia , Tolerância a Antígenos Próprios , Timo/patologia , Animais , Autoantígenos/análise , Autoantígenos/imunologia , Linfócitos T CD4-Positivos/imunologia , Feminino , Doença Enxerto-Hospedeiro/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Ovalbumina/imunologia , Timo/imunologiaRESUMO
Development of acute graft-versus-host disease (aGVHD) predisposes to chronic GVHD with autoimmune manifestations. A characteristic of experimental aGVHD is the de novo generation of autoreactive T cells. Central tolerance is dependent on the intrathymic expression of tissue-restricted peripheral self-antigens (TRA), which is in mature medullary thymic epithelial cells (mTEC(high)) partly controlled by the autoimmune regulator (Aire). Because TECs are targets of donor T-cell alloimmunity, we tested whether murine aGVHD interfered with the capacity of recipient Aire(+)mTEC(high) to sustain TRA diversity. We report that aGVHD weakens the platform for central tolerance induction because individual TRAs are purged from the total repertoire secondary to a decline in the Aire(+)mTEC(high) cell pool. Peritransplant administration of an epithelial cytoprotective agent, fibroblast growth factor-7, maintained a stable pool of Aire(+)mTEC(high), with an improved TRA transcriptome despite aGVHD. Taken together, our data provide a mechanism for how autoimmunity may develop in the context of antecedent alloimmunity.
Assuntos
Antígenos/genética , Células Epiteliais/imunologia , Doença Enxerto-Hospedeiro/genética , Doença Enxerto-Hospedeiro/imunologia , Timo/metabolismo , Doença Aguda , Animais , Antígenos/metabolismo , Autoantígenos/genética , Autoantígenos/metabolismo , Feminino , Expressão Gênica/fisiologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Camundongos Transgênicos , Timo/patologiaRESUMO
Allogeneic HCT is a potentially curative treatment strategy for patients with inborn errors of immunities (IEIs). Objective of this study was to assess the optimal busulfan exposure prior to allogeneic HCT for patients with an IEI who received an intravenous busulfan-based conditioning regimen between 2000 and 2023. Patients from 17 international centers were included. Main outcome of interest was event-free survival (EFS). Patients were categorized into 4 IEI subgroups: combined-immunodeficiency (CID), severe combined immunodeficiency (SCID), neutrophil disorders and hemophagocytic lymphohistiocytosis (HLH)-related disorders. Busulfan exposure was calculated by individual centers (AUCCENTER) and was re-estimated using a validated model (AUCNONMEM). Overall, 562 patients were included: 173 (30.8%) CID, 154 (27.4%) SCID, 101 (18.0%) HLH-related disorders, and 134 (23.8%) neutrophil disorders. Median busulfan AUCNONMEM was 69.0 mg×h/L and correlated poorly with AUCCENTER (r2=0.54). Patients with SCID, HLH-related, and neutrophil disorders were analyzed together (n=389), because CID disease subtype was an effect modifier (p=0.03). Estimated 2-year EFS was 78.5%. In patients with the found optimal busulfan AUCNONMEM of 70-90 mg×h/L, 2-year EFS was superior to <70 mg×h/L (adj-HR 1.97, 95% CI 1.11-3.49, p=0.02), and >90 mg×h/L (adj-HR 5.05, 95% CI 2.43-10.49, p<0.0001). Full donor chimerism increased with higher busulfan AUCNONMEM, plateauing at 90 mg×h/L. For CID patients, optimal AUCNONMEM for donor chimerism was found to be >70 mg×h/L. Improved EFS and higher donor chimerism may be achieved by targeting a cumulative busulfan AUCNONMEM of 80 mg×h/L (range 70-90). Our study stresses the importance to uniformly using a validated population PK-model to estimate the AUCNONMEM.
RESUMO
Reaching target exposure of busulfan-based conditioning prior to hematopoietic stem cell transplantation is vital for favorable therapy outcomes. Yet, a wide inter-patient and inter-occasion variability in busulfan exposure has been reported, especially in children. We aimed to identify factors associated with the variability of busulfan pharmacokinetics in 124 consecutive patients transplanted at the University Children's Hospital Zurich between October 2010 and February 2020. Clinical data and busulfan plasma levels after twice-daily intravenous administration were analyzed retrospectively by population pharmacokinetic modeling. The volume of distribution correlated with total body water. The elimination rate constant followed an age-dependent maturation function, as previously suggested, and correlated with the levels of serum albumin. Acute lymphoblastic leukemia reduced busulfan clearance by 20%. Clearance significantly decreased by 17% on average from the start to the third day of busulfan administration, in agreement with other studies. An average reduction of 31% was found in patients with hemophagocytic lymphohistiocytosis and X-linked lymphoproliferative disease. In conclusion, we demonstrate that in addition to known factors, underlying disease and serum albumin significantly impact busulfan pharmacokinetics in pediatric patients; yet, substantial unexplained variability in some patients remained. Thus, we consider repeated pharmacokinetic assessment essential to achieve the desired target exposure in twice-daily busulfan administration.
RESUMO
Thymic epithelial cells (TECs) are essential in supporting the development of mature T cells from hematopoietic progenitor cells and facilitate their lineage-commitment, proliferation, T-cell receptor repertoire selection and maturation. While animal model systems have greatly aided in elucidating the contribution of stromal cells to these intricate processes, human tissue has been more difficult to study, partly due to a lack of suitable surface markers comprehensively defining human TECs. Here, we conducted a flow cytometry based surface marker screen to reliably identify and quantify human TECs and delineate medullary from cortical subsets. These findings were validated by transcriptomic and histologic means. The combination of EpCAM, podoplanin (pdpn), CD49f and CD200 comprehensively identified human TECs and not only allowed their reliable distinction in medullary and cortical subsets but also their detailed quantitation. Transcriptomic profiling of each subset in comparison to fibroblasts and endothelial cells confirmed the identity of the different stromal cell subsets sorted according to the proposed strategy. Our dataset not only demonstrated transcriptional similarities between TEC and cells of mesenchymal origin but furthermore revealed a subset-specific distribution of a specific set of extracellular matrix-related genes in TECs. This indicates that TECs significantly contribute to the distinct compartmentalization - and thus function - of the human thymus. We applied the strategy to quantify TEC subsets in 31 immunologically healthy children, which revealed sex-specific differences of TEC composition early in life. As the distribution of mature CD4- or CD8-single-positive thymocytes was correspondingly altered, the composition of the thymic epithelial compartment may directly impact on the CD4-CD8-lineage choice of thymocytes. We prove that the plain, reliable strategy proposed here to comprehensively identify human TEC subpopulations by flow cytometry based on surface marker expression is suitable to determine their frequency and phenotype in health and disease and allows sorting of live cells for downstream analysis. Its use reaches from a reliable diagnostic tool for thymic biopsies to improved phenotypic characterization of thymic grafts intended for therapeutic use.
Assuntos
Separação Celular , Células Epiteliais/metabolismo , Citometria de Fluxo , Perfilação da Expressão Gênica , Células Estromais/metabolismo , Timo/metabolismo , Transcriptoma , Síndrome da Deleção 22q11/genética , Síndrome da Deleção 22q11/imunologia , Síndrome da Deleção 22q11/metabolismo , Adolescente , Fatores Etários , Biomarcadores/metabolismo , Criança , Pré-Escolar , Deleção Cromossômica , Cromossomos Humanos Par 22 , Células Epiteliais/imunologia , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Miastenia Gravis/genética , Miastenia Gravis/imunologia , Miastenia Gravis/metabolismo , Fenótipo , Fatores Sexuais , Células Estromais/imunologia , Timo/citologia , Timo/imunologiaRESUMO
The thymus constitutes the primary lymphoid organ responsible for the generation of naive T cells. Its stromal compartment is largely composed of a scaffold of different subsets of epithelial cells that provide soluble and membrane-bound molecules essential for thymocyte maturation and selection. With senescence, a steady decline in the thymic output of T cells has been observed. Numeric and qualitative changes in the stromal compartment of the thymus resulting in reduced thymopoietic capacity have been suggested to account for this physiologic process. The precise cellular and molecular mechanisms underlying thymic senescence are, however, only incompletely understood. Here, we demonstrate that TGF-beta signaling in thymic epithelial cells exerts a direct influence on the cell's capacity to support thymopoiesis in the aged mouse as the physiologic process of thymic senescence is mitigated in mice deficient for the expression of TGF-beta RII on thymic epithelial cells. Moreover, TGF-beta signaling in these stromal cells transiently hinders the early phase of thymic reconstitution after myeloablative conditioning and hematopoietic stem cell transplantation. Hence, inhibition of TGF-beta signaling decelerates the process of age-related thymic involution and may hasten the reconstitution of regular thymopoiesis after hematopoietic stem cell transplantation.
Assuntos
Envelhecimento/fisiologia , Células Epiteliais/fisiologia , Transplante de Células-Tronco Hematopoéticas/efeitos adversos , Regeneração , Timo/fisiologia , Fator de Crescimento Transformador beta/fisiologia , Animais , Camundongos , Transdução de Sinais , Células Estromais , Timo/citologiaRESUMO
Reduced-intensity/reduced-toxicity conditioning and allogeneic T-cell replete hematopoietic stem cell transplantation are curative in patients with hemophagocytic lymphohistiocytosis (HLH). Unstable donor chimerism (DC) and relapses are clinical challenges . We examined the effect of a reduced-intensity conditioning regimen based on targeted busulfan to enhance myeloid DC in HLH. The European Society for Bone and Marrow Transplantation-approved reduced-intensity conditioning protocol comprised targeted submyeloablative IV busulfan, IV fludarabine, and serotherapy comprising IV alemtuzumab (0.5-0.8 mg/kg) for unrelated-donor and IV rabbit anti-T-cell globulin for related-donor transplants. We assessed toxicity, engraftment, graft-versus-host disease (GHVD), DC in blood cell subtypes, and overall survival/event-free survival. Twenty-five patients from 7 centers were treated (median age, 0.68 year). The median total dose and cumulative area under the curve of busulfan was 13.1 mg/kg (6.4-26.4) and 63.1 mg/L × h (48-77), respectively. Bone marrow, peripheral blood stem cell, or cord blood transplants from HLA-matched related (n = 7) or unrelated (n = 18) donors were administered. Donor cells engrafted in all patients (median: neutrophils d+20/platelets d+28). At last follow-up (median, 36 months; range, 8-111 months), the median DC of CD15+ neutrophils, CD3+ T cells, and CD16+56+ natural killer cells was 99.5% (10-100), 97% (30-100), and 97.5% (30-100), respectively. Eight patients (32%) developed sinusoidal obstruction syndrome, resolving after defibrotide treatment. The 3-year overall survival and event-free survival rates were both 100%. None of the patients developed acute grade III to IV GHVD. Limited chronic GVHD was encountered in 4%. This regimen achieves excellent results with stable DC in patients with HLH.
Assuntos
Transplante de Células-Tronco Hematopoéticas , Linfo-Histiocitose Hemofagocítica , Animais , Bussulfano , Humanos , Linfo-Histiocitose Hemofagocítica/terapia , Recidiva Local de Neoplasia , Coelhos , Condicionamento Pré-TransplanteRESUMO
We describe a case of an infant diagnosed with severe combined immune deficiency (Adenosine Deaminase (ADA), SCID) with severe retinopathy and associated low vision in both eyes at first examination. An extensive infectious work up revealed an enterovirus infection, which suggested an early infectious and severe retinopathy. Genetic causes of congenital retinitis pigmentosa/ Leber's congenital amaurosis could be excluded by whole exome sequencing.
Assuntos
Infecções por Enterovirus/diagnóstico , Infecções Oculares Virais/diagnóstico , Doenças Retinianas/diagnóstico , Imunodeficiência Combinada Severa/diagnóstico , DNA Viral/genética , Enterovirus/genética , Enterovirus/isolamento & purificação , Infecções por Enterovirus/virologia , Infecções Oculares Virais/virologia , Fezes/virologia , Feminino , Seguimentos , Humanos , Lactente , Reação em Cadeia da Polimerase , Doenças Retinianas/virologia , Imunodeficiência Combinada Severa/terapia , Imunodeficiência Combinada Severa/virologia , Transplante de Células-Tronco , Baixa Visão/diagnóstico , Sequenciamento do ExomaRESUMO
Acute graft-versus-host disease (aGVHD) impairs thymus-dependent T-cell regeneration in recipients of allogeneic bone marrow transplants through yet to be defined mechanisms. Here, we demonstrate in mice that MHC-mismatched donor T cells home into the thymus of unconditioned recipients. There, activated donor T cells secrete IFN-gamma, which in turn stimulates the programmed cell death of thymic epithelial cells (TECs). Because TECs themselves are competent and sufficient to prime naive allospecific T cells and to elicit their effector function, the elimination of host-type professional antigen-presenting cells (APCs) does not prevent donor T-cell activation and TEC apoptosis, thus precluding normal thymopoiesis in transplant recipients. Hence, strategies that protect TECs may be necessary to improve immune reconstitution following allogeneic bone marrow transplantation.