Donor Neutrophils and B Cells in EVLP Perfusate are Associated with Severe Primary Graft Dysfunction

Abstract

<h3>Purpose</h3> Primary graft dysfunction (PGD) remains a major obstacle to lung transplantation (LT) success and is classified as severe (PGD3) in 10-15% of all LT recipients. Ex vivo lung perfusion (EVLP) allows for evaluation of donor lungs prior to LT and measurement of circulating cells and soluble factors in the perfusate. The contributions of donor cells to PGD are unknown, and whether specific cells might confer a risk of PGD is unclear. We hypothesized that larger quantities of donor myeloid cells in EVLP perfusate might predict PGD3. <h3>Methods</h3> In this retrospective study, we selected consecutive clinical EVLP cases and grouped them based on Pa_O2/F_IO2 (P/F) ratio at 72h post-LT, resulting in two groups: PGD3 (n = 33, P/F = 183 ± 48mmHg) and PGD0/1 (n = 25, P/F = 395 ± 71mmHg). Cryopreserved perfusate cells from the first and last hour of EVLP were subjected to multiparameter flow cytometry to identify major leukocyte populations. Time and PGD-dependent differences were assessed by two-way ANOVA with post-hoc testing adjusted for multiple comparisons. <h3>Results</h3> In the first hour of EVLP, the total cells/mL was higher in the PGD3 group compared to PGD0/1 (12.1 × 10⁵ versus 8.4 × 10⁵ cells/ml, p = 0.0573) - the cell/ml decreased in both groups to similar densities by the end of EVLP (Fig A). In the PGD3 group, neutrophils (Fig B) and B cells (Fig C) were significantly higher than in the PGD0/1 group in the first hour and significantly decreased over time. Macrophages (Fig D) and classical monocytes (Fig E) were also elevated in PGD3 group in the first hour, although this observation did not reach statistical significance. <h3>Conclusion</h3> Neutrophils and B cells in the 1-hour perfusate are associated with PGD3 development at 72h post-LT. While these findings suggest that higher numbers of these donor cells may play a role in PGD pathogenesis, PGD3 developed even though these populations were reduced by the end of EVLP. Studies of cellular activation states will be conducted to validate these findings and explore donor cellular contributions to PGD.