A post-preservation vascular flush removes significant populations of donor leukocytes prior to lung transplantation.

Ball AL, Edge RJ, Amin K, Critchley WR, Howell GJ, Yonan N, Stone JP, Fildes JE. Transpl Immunol. 2020 Nov 29;64:101356. doi: 10.1016/j.trim.2020.101356. Online ahead of print. PMID: 33264679

Background: Donor leukocytes are intrinsically involved in acute lung allograft rejection, via self-presentation of donor antigens to recipient leukocytes. Therapeutic modalities to remove donor leukocytes are currently unavailable. We evaluated if a vascular flush immediately following preservation can be used for this purpose.

Methods: A post-preservation flush was performed with STEEN solution in n = 6 porcine lungs following static cold storage. The first 500 ml effluent from the left atrium was collected and an inflammatory profile performed.

Results: A total of 1.17 billion (±2.8 × 108) viable leukocytes were identified within the effluent. T cells were the dominant cell population, representing 82% of the total mobilisedleukocytes, of which <0.01% were regulatory T cells. IL-18 was the most abundant cytokine, with a mean concentration of 84,216 pg (±153,552 pg). In addition, there was a mean concentration of 8819 ng (±4415) cell-free mitochondrial DNA.

Conclusion: There is an immediate transfer of donor leukocytes, cytokines and damage-associated molecular patterns following reperfusion. Such a pro-inflammatory donor load may enhance alloantigen presentation and drive recipient alloimmune responses. A post-preservation flush may therefore be an effective method for reducing the immune burden of the donor lung prior to transplantation.