Lung Transplantation and Immune Tolerance in Young Recipients

描述（由申请人提供）：患有包括囊性纤维化在内的遗传性肺疾病的儿童可能需要肺移植。然而，急性排斥反应次数增加的患者有发展为慢性排斥反应（闭塞性细支气管炎[OB]）的风险。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（mixed hematopoietic chimerism， 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），并与器官特异性耐受的发展有关。同种异体肺移植已经成功地从造血细胞（HC）供体移植到具有稳定MC的受体而无需免疫抑制。这些受者长期随访，未出现急性或慢性排斥反应。这种HC和肺移植耐受模型已被进一步表征，其结果与涉及调节性（CD4+ CD25+） T细胞的外周机制一致。在去除CD4+ CD25+调节性T细胞后，受体来源的供体特异性同种反应性T细胞可以在体外与供体来源的实体器官移植混合造血嵌合体的血液中鉴定。因此，在这种免疫耐受模型中，没有观察到缺失机制做出重大贡献。这与MC的啮齿动物模型相反，在啮齿动物模型中，已经观察到缺失机制，并推测在建立耐受性方面起着相当大的作用。耐受的调节机制也可能与没有造血干细胞移植的肺移植有关。因此，这项拨款提案的目标是在大型动物模型（狗）中进一步研究调节性T细胞在诱导对同种异体肺移植免疫耐受中的作用。我们已经建立了调节性T细胞体外扩增的方法，并且可以产生足够数量的调节性T细胞进行体内研究。我们将研究体外扩增受体衍生的CD4+CD25+调节性T细胞无HCT累加是否安全，并将在年轻受体（4-6个月大）中实现延长肺移植存活的目标。将评估调节性T细胞联合肺移植的细胞剂量和调度策略。体外扩增的调节细胞输注后的命运也将被表征。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性以预防急性和慢性排斥反应的临床前策略的发展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.