Abnormal CD4/CD8 Ratio prior to Lung Transplantation is Linked to Decreased CLAD-free Survival

<bold>Intro:</bold> Chronic lung allograft dysfunction (CLAD) is the major limitation of long-term survival after lung transplantation (LuTx). Comprehensive understanding of the immunological factors contributing to its development remains elusive, and the susceptibility to immune dysregulation may begin even prior to LuTx. Our objective was to determine the impact of dysregulated CD4/CD8 lymphocytes ratio (rCD) prior to LuTx on CLAD-free survival. <bold>Methods:</bold> Patients transplanted between 2010 and 2019, with an available rCD measurement within 24 hours preceding the LuTx procedure, and who were subsequently followed up at our centre, were included. LuTx recipients (LTRs) were divided according to rCD into normal (N-rCD; rCD 1.1 - 3.0) and abnormal rCD group (AN-rCD; rCD ≤1 or >3). CLAD onset was determined in accordance with the ISHLT 2019 consensus. Log rank survival analysis was performed. <bold>Results:</bold> 163 LTRs were included. N-rCD consisted of 108 LTRs [66.3%; median rCD 1.7 (IQR 1.3-2.1)] and AN-rCD of 55 patients [33.7%; median rCD 0.7 (IQR 0.5 - 0.9) for rCD ≤1 and 3.9 (IQR 3.45-4.9) for rCD >3]. Median CLAD-free survival was 2130 days for N-rCD and 605 days for AN-rCD, p=0.0003 (Figure). <bold>Conclusion:</bold> CLAD-free survival was significantly reduced in LTRs with abnormal CD4/CD8 ratio prior to LuTx. Dysregulation of T-lymphocytes prior to LuTx might substantially impact allograft immune tolerance and susceptibility to infections, which requires further investigation.