Lung Transplantation and Immune Tolerance in Young Recipients

描述（由申请人提供）：患有涉及肺的遗传性疾病（包括囊性纤维化）的儿童可能需要肺移植。然而，急性排斥发作次数增加的患者有发生慢性排斥的风险（闭塞性细支气管炎[OB]）。这导致5年生存率低于50%。需要新的策略来预防肺移植后的急性和慢性排斥反应。混合造血嵌合体（MC）的建立需要对造血组织的双向耐受（移植物对宿主和宿主对移植物），并且与器官特异性耐受的发展相关。肺移植已成功地从造血细胞（HC）供体移植到受体与稳定MC，而不需要免疫抑制剂。这些受体已被长期随访，没有发生急性或慢性排斥反应。这种HC和肺移植物耐受模型已被进一步表征，并且发现与涉及调节性（CD 4 + CD 25+）T细胞的外周机制一致。在去除CD 4 + CD 25+调节性T细胞后，可以在来自具有供体来源的实体器官移植物的混合造血嵌合体的血液中体外鉴定受体来源的供体特异性同种异体反应性T细胞。因此，在该免疫耐受模型中，未观察到缺失机制做出显著贡献。这与啮齿类动物模型的MC，其中删除机制已被观察到，并推测有相当大的作用，在建立耐受性。耐受性的调节机制也可能与在没有造血干细胞移植物的情况下的肺移植物的移植有关。因此，本基金的目的是进一步研究调节性T细胞在诱导大型动物模型（犬）肺同种异体移植免疫耐受中的作用。我们已经建立了体外扩增调节性T细胞的方法，并可以产生足够的数量进行体内研究。我们将研究在没有HCT的情况下，体外扩增的受体来源的CD 4 + CD 25+调节性T细胞的回加是否安全，并且是否将实现在年轻受体（4-6个月大）中延长肺移植物存活的目标。将评估调节性T细胞的回加与肺移植组合的细胞给药和调度策略。还将表征输注后离体扩增的调节细胞的命运。这将有助于理解这些细胞在建立耐受性中的作用。在大型动物模型中诱导肺特异性耐受以预防急性和慢性排斥反应的临床前策略的开发将增加成功转化为人类研究的可能性。

DESCRIPTION (provided by applicant): Children with genetic diseases involving the lung including cystic fibrosis may require lung transplantation. However patients who experience an increased number of acute rejection episodes are at risk for the development of chronic rejection (obliterative bronchiolitis [OB]). This results in a 5-year survival of less than 50%. New strategies to prevent acute and chronic rejection after lung transplantation are required. The establishment of mixed hematopoietic chimerism (MC) requires 2-way tolerance (graft vs. host and host vs. graft) to hematopoietic tissue and is associated with the development of organ-specific tolerance. Lung allografts have been successfully transplanted from the hematopoietic cell (HC) donor to recipients with stable MC without the need for immunosuppression. These recipients have been followed long-term without the development of acute or chronic rejection. This model of HC and lung graft tolerance has been further characterized and the findings are consistent with a peripheral mechanism involving regulatory (CD4+ CD25+) T cells. Recipient-derived donor-specific alloreactive T cells can be identified in vitro in blood from mixed hematopoietic chimeras with a donor-derived solid organ graft after removal of CD4+ CD25+ regulatory T cells. Therefore in this model of immune tolerance, deletional mechanisms have not been observed to make a significant contribution. This is in contrast to rodent models of MC in which deletional mechanisms have been observed and presumed to have a considerable role in the establishment of tolerance. Regulatory mechanisms of tolerance may also be relevant for transplantation of lung grafts in the absence of a hematopoietic stem cell graft. Therefore the goal of this grant proposal is to further investigate the role of regulatory T cells in the induction of immune tolerance to lung allografts in a large animal model (dog). We have established the methods for ex vivo expansion of regulatory T cells and can produce sufficient quantities to conduct in vivo studies. We will investigate if addback of ex vivo expanded recipient derived CD4+CD25+ regulatory T cells without HCT is safe and will achieve the goal of prolonged lung graft survival in young recipients (4-6 months old). Cell dosing and scheduling strategies for addback of regulatory T cells in combination with lung transplantation will be assessed. Fate of the ex vivo expanded regulatory cells after infusion will also be characterized. This will contribute to the understanding of the role these cells have in the establishment of tolerance. Development of preclinical strategies for the induction of lung-specific tolerance in large animal models to prevent acute and chronic rejection will increase the probability of successful translation to human studies.