IDENTIFYING LEUKOCYTE POPULATIONS AS BIOMARKERS FOR CHRONIC LUNG ALLOGRAFT DYSFUNCTION

Lung transplantation (LT) is a life-saving therapy for end-stage respiratory diseases, but long-term survival is limited by chronic lung allograft dysfunction (CLAD). Early detection is essential to prevent irreversible damage. To determine which leukocyte populations in peripheral blood are altered in CLAD after bilateral LT, in order to identify potential biomarkers for improved diagnosis. A case-control study included 68 bilateral LT recipients (LTR): Stable LTR (n=29), Established CLAD (n=28), and De novo CLAD (n=11). Leukocyte subpopulations were analyzed by flow cytometry using five DuraClone panels (basic phenotyping, TCRs, Treg, granulocytes and dendritic cells (DC)). Absolute counts were quantified with Flow-Count fluorospheres. Five leukocyte subpopulations differed significantly between groups. De novo CLAD patients showed reduced plasmacytoid DCs (HLA-DR+ Lin- CD123+ CD11c-), conventional DCs type 1 (HLA-DR+ Lin- CD123- CD11c+ CD16- Clec9A+), and regulatory NK cells (CD56high CD16-) compared with stable LTR ( Fig. 1 ). Additional differences were found in TCRγδ+Vδ2+ T cells and Helios+CD39- Tregs. Reduced levels of plasmacytoid DCs, cDC1, and NKreg cells suggest a role for impaired regulatory immune subsets in CLAD onset and highlight their potential as biomarkers for early detection.