Alterations in Perfusate Leukocyte Populations are Associated with Donor Mode of Death and the Outcome of Ex Vivo Lung Perfusion

Abstract

Lung transplantation (LTx) is limited by the scarcity of suitable donor lungs. One option to expand the donor pool is the use of donation after circulatory death (DCD) lungs. Additionally, ex vivo lung perfusion (EVLP) allows for evaluation and treatment of donor lungs prior to LTx. There are limited data describing the cellular, specifically leukocyte populations in EVLP perfusate, and their link to donor mode of death. We hypothesized that EVLP perfusate leukocytes differ between DCD and neurological determination of death (NDD) lungs, and between lungs accepted and declined for transplant. EVLP perfusates were sampled hourly from clinical EVLP cases until termination. Perfusate cells were separated and cryopreserved. The first and last available perfusate from lungs accepted (n = 10 NDD and n = 10 DCD) and declined (n = 10 NDD and n = 10 DCD) for LTx were selected and stained with flow cytometry panels to characterize major leukocyte populations. Lymphoid cells form the majority of perfusate cells (Fig A). B cells were significantly higher in declined lungs regardless of mode of donor death (Fig B). CD4+ memory T cells (CD3+ CD4+ CD45RO+) and activated CD8+ T cells (CD3+ CD8+ CD25+) were elevated in the DCD lung perfusates (Fig C). In all groups, CD163hi, HLA-DR+ monocytes were observed at first available perfusate and diminished at the end of EVLP, while neutrophils were low in the first perfusate sample but increased significantly by the end of EVLP (Fig D). Interestingly, leukocyte populations in EVLP perfusate differ between mode of donor death, with lower levels of B cells associated with lungs accepted for transplant, and certain T cell subsets over-represented in DCD lungs. While no significant changes were observed in myeloid cells, their kinetics over time vary based on cell type. Future studies will be required to determine the sources of these cell populations and whether they are involved in the pathogenesis of lung injury prior to transplant.