PS74. Thermal Preconditioning During EVLP Reduces T Lymphocytes and Increases Monocytes and Neutrophils Contents in the Perfusion Solution.

Los Angeles Convention Center 

Objective: We previously demonstrated that lung subjected to a mild thermal preconditioning (TP) of 41.5°C during ex vivo lung perfusion (EVLP) had improved function and decreased inflammatory and cell death markers. How TP affects the populations of immune cells in the lung airways and the perfusion solution after EVLP is the purpose of this study.
Methods: Male rats were randomly assigned into 2 groups: controls (Ctl, n=7) or TP (n=9). Lungs were kept in situ for 1h at room temperature and flushed with cold Perfadex. The heart-lung block was harvested, kept at 4°C for 1h and mounted on the EVLP system. In the Ctl group, the temperature of the perfusion solution was kept at 37°C. In the TP group, a heat shock was done after 1h of EVLP by heating the perfusion solution to 41.5°C for 30 minutes. At the end of EVLP, we sampled and centrifuged the bronchoalveolar lavage fluid (BALF) and the perfusion solution to collect cells. The BALF and perfusion solution contents of B lymphocytes, CD4+ and CD8+ T lymphocytes as well as contents in macrophages, monocytes and granulocytes were analyzed by flow cytometry and expressed as the percentages of live cells.
Results: We did not observe significant differences in total live cell counts in the perfusate and the BALF between the Ctl and TP groups. In the BALF, the proportions of immune cells were unchanged by TP as compared to Ctl. In the perfusate, we observed a significant reduction in T cells populations in TP group as compared to Ctl. CD4+ T cells were 40.5 ± 8.7% of viable cells in Ctl group and 26.9±4.5% (p=0.001) in the TP group. CD8+ were 25.8 ± 3.8% in Ctl and 19.6 ± 3.8% in TP (p=0.005). B lymphocytes were not changed (15.6 ± 5.2% in Ctl vs 18.8 ± 6.2% in TP). The proportion of myeloid cells were increased in TP with 14.0 ± 5.1% in Ctl and 23.7 ± 5.0% in TP (p=0.002). Myeloid cells were predominantly monocytes (13.3 ± 4.9% in Ctl and 21.5± 4.9% in TP (p=0.003)) and neutrophils (0.4 ± 0.3% in Ctl and 1.7± 1.0% in TP (p=0.005)).
Conclusion: TP during EVLP reduces T lymphocytes and augments monocytes and neutrophils proportions in the perfusion solution. Whether this results from changes in endothelium adhesion capability or permeability in responses to TP and/or immune cell type specific responses to TP will need more investigations. This underlines the profound effects of TP on immune responses and opens an exciting field of research.

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