Lung transplantation remains limited by a lack of donor organs available for transplant and a reduced median survival secondary to allograft rejection and graft dysfunction. Upon donor death, a catecholamine and cytokine storm ensues, resulting in inflammatory cell infiltration within the lung. Reperfusion of such immunologically primed donor lungs can then drive a heightened recipient immune response. Despite this, the donor immune compartment is often ignored. The aim of this PhD was to characterise the effects of reperfusion upon the donor immune compartment and the recipient response, to identify potential biomarkers and avenues for manipulation. A porcine model was used to determine whether EVLP could alter the inflammatory signalling profile of the donor lung upon transplantation. Indeed, a global up-regulation of cell-survival proteins was observed within EVLP transplanted lungs, yet not in lungs that underwent standard transplant. Increased levels of cell-free mtDNA were also detected in the recipient circulation following standard transplant. The capability of EVLP to facilitate the mobilisation of inflammatory mediators from the lung prior to transplantation was explored. A secondary preservation flush was performed to characterise the immune content of the donor lung following cold ischaemic storage. The migratory pattern of donor leukocytes during EVLP was also elucidated, to determine whether a continual non-recirculating perfusion flush could reduce the donor leukocyte burden prior to transplantation. In addition, cell-free levels of mtDNA were also quantified during human and porcine EVLP, and in the recipient circulation post human lung transplantation. These levels were then correlated with functional and clinical outcomes to determine whether mtDNA is a biomarker of lung function. The study demonstrated that the donor immune compartment is comprised of a large repertoire of donor leukocytes that readily migrate from the lung upon immediate revascularisation. A continual flush with non-recirculating perfusate facilitated the removal of 9 billion donor leukocytes, yet upon perfusate recirculation, donor leukocyte migration continued. The overwhelming propensity of the donor leukocyte repertoire to mobilise upon revascularisation demonstrates the need to consider donor leukocyte depletion prior to transplantation. Furthermore, cell-free mtDNA was observed to correlate with injury on the EVLP circuit, and the incidence of chronic graft dysfunction post-transplantation, highlighting its potential to serve as a biomarker in lung transplantation.