Analysis of long term CD4+CD25highCD127- T-reg cells kinetics in peripheral blood of lung transplant recipients

BACKGROUND The role of CD4+CD25highCD127- T-reg cells in solid-organ Transplant (Tx) acceptance has been extensively studied. In previous studies on kidney and liver recipients, peripheral T-reg cell counts were associated to graft survival, while in lung Tx, there is limited evidence for similar findings. This study aims to analyze long term peripheral kinetics of T-reg-cells in a cohort of lung recipients and tests its association to several clinical variables. METHODS From jan 2009 to dec 2014, 137 lung Tx recipients were submitted to an immunological follow up (median: 105.9 months (6.7-310.5)). Immunological follow up consisted of a complete blood peripheral immuno-phenotype, inclusive of CD4+CD25highCD127- T and FOXP3+ cells. We tested the association between T-reg and relevant variables by linear OR regression models for repeated measures, adjusting for time from Tx. Also, by ordered logistic models for panel data, the association between Chronic Lung Allograft Dysfuncton (CLAD) onset/progression and T-reg counts in the previous 3 months was tested. RESULTS Among all variables analyzed at multivariate analysis: Bronchiolitis Obliterans Syndrome (OR -6.51, p < 0.001), Restrictive Allograft Syndrome (OR -5.19, p = 0.04) and Extracorporeal photopheresis (OR -5.65, p < 0.001) were significantly associated to T-reg cell. T-reg cell counts progressively decreased according to the severity of CLAD. Furthermore, patients with higher mean T-reg counts in a trimester had a significantly lower risk (OR 0.97, p = 0.012) of presenting CLAD or progressing in the graft dysfunction in the following trimester. CONCLUSIONS Our present data confirm animal observations on the possible role of T-reg in the evolution of CLAD.