High CD4/CD8 Ratio prior to Lung Transplantation is Associated with an Increased Risk of Primary Graft Dysfunction at 48 hours

Intro: Primary graft dysfunction (PGD) represents a spectrum of early lung allograft alterations resulting in hypoxemia and lung edema. The precise pathophysiology of PGD remains unknown, however, imbalance in T-lymphocytes prior to lung transplantation (LuTx) might be a potential risk factor for subsequent immunopathological events. We aimed to investigate the relationship between dysregulation of T-lymphocytes CD4/CD8 ratio (rCD) prior to LuTx and risk of PGD development. <bold>Methods:</bold> Patients transplanted between 2018-2022, with available both rCD measurement 24h prior to LuTx and PGD evaluation at 48 and 72h were included. Patients with severe pulmonary hypertension on protocolar prolonged ECMO after LuTx were excluded. LuTx recipients (LTRs) were divided according to rCD into low (L-rCD; rCD ≤1), normal (N-rCD; rCD 1.1 - 3.0) and high rCD group (H-rCD; rCD >3) and matched with their respective PGD grades. Analyses were performed using Kruskal-Wallis test. <bold>Results:</bold> A total of 149 LTRs were included. The L-rCD comprised 32 patients [21%; median rCD 0.7 (IQR 0.5-0.9)], the N-rCD of 94 [63%; median rCD 1.7; IQR 1.3-2.2] and H-rCD of 23 [15%; median rCD 3.6 (IQR 3.35-4.7)]. At 48h, PGD ≥2 occurred in 6% of the L-rCD, in 7% of the N-rCD, and 35% of the H-rCD LTRs (p=0.012). At 72h, PGD ≥2 occurred in 9% of the L-rCD, in 8% of the N-rCD, and 17% of the H-rCD LTRs (p=NS). <bold>Conclusion:</bold> A significantly increased risk of developing a higher grade of PGD at 48h was observed in H-rCD. We hypothesized that upregulated CD4-T cells might enhance a more potent immune response, which requires further investigation.