The Frequency of Tissue-Resident Donor T and NK Cells in Peripheral Blood after Lung Transplantation is Modulated by Normothermic Ex Vivo Lung

Abstract

Purpose The appearance of passenger donor lymphocytes in recipient blood after double lung transplantation has been described decades ago. However, neither their early kinetics, nor distribution of lymphocyte subsets and clinical relevance have been addressed in detail. Therefore, we investigated frequencies and phenotypes of donor T and NK cells within the first 24 hours and at 3 weeks after lung transplantation and correlated them to important clinical outcomes. Methods Blood and perfusion solutions of 59 lung recipients (30 male, 29 female, median age 51) were analysed pre Tx, at T0, T24 and at three weeks (3wk) for NK and T cell subsets. In a subset of 20 patients with standard cold donor lung preservation and 9 preserved with portable ex vivo lung preservation (OCS Lung), donor T and NK cells were identified in blood by staining of donor HLA alleles (HLA-A1,A2,A11,A24) combined with lineage markers. Frequencies of donor lymphocytes were correlated to cold ischemic time (CIT), primary graft dysfunction (PGD) and chronic lung allograft dysfunction (CLAD). Results In all lung recipients, the NK cell frequency was significantly increased at T0 and T24 (p=0.04), CD4 T cells decreased and CD8 T cells remained stable. No significant differences were seen between recipients of standard vs OCS preserved lungs. Donor NK cells comprised 18.8% at T0, 17.1% at T24 and 7.8% at 3 wk (p<0.001) of circulating NK cells. Frequencies were for donor CD8+ T cells 8.3%, 6.6% and 2.6%, and for CD4+ donor T cells 6.4%, 4.6% and 1.3% of the respective subset. At T0, significantly less donor NK cells were detected in recipients of OCS lungs (p<0.008), while T cells were reduced non-significantly. No correlation between donor NK or T cell frequencies was observed for CIT or PGD. In the limited number of patients at risk, a trend towards higher early donor T cell frequencies in recipients not developing CLAD at two years after Tx was observed (p=0.04). Conclusion Donor T and NK cells are detectable in blood of all lung recipients during the first 3 weeks after Tx and did not correlate with CIT or PGD. Preservation with portable EVLP resulted in decreased NK cell frequencies which might be explained by their ex vivo mobilization. Furthermore, transient donor chimerism might have a protective effect against CLAD development. The appearance of passenger donor lymphocytes in recipient blood after double lung transplantation has been described decades ago. However, neither their early kinetics, nor distribution of lymphocyte subsets and clinical relevance have been addressed in detail. Therefore, we investigated frequencies and phenotypes of donor T and NK cells within the first 24 hours and at 3 weeks after lung transplantation and correlated them to important clinical outcomes. Blood and perfusion solutions of 59 lung recipients (30 male, 29 female, median age 51) were analysed pre Tx, at T0, T24 and at three weeks (3wk) for NK and T cell subsets. In a subset of 20 patients with standard cold donor lung preservation and 9 preserved with portable ex vivo lung preservation (OCS Lung), donor T and NK cells were identified in blood by staining of donor HLA alleles (HLA-A1,A2,A11,A24) combined with lineage markers. Frequencies of donor lymphocytes were correlated to cold ischemic time (CIT), primary graft dysfunction (PGD) and chronic lung allograft dysfunction (CLAD). In all lung recipients, the NK cell frequency was significantly increased at T0 and T24 (p=0.04), CD4 T cells decreased and CD8 T cells remained stable. No significant differences were seen between recipients of standard vs OCS preserved lungs. Donor NK cells comprised 18.8% at T0, 17.1% at T24 and 7.8% at 3 wk (p<0.001) of circulating NK cells. Frequencies were for donor CD8+ T cells 8.3%, 6.6% and 2.6%, and for CD4+ donor T cells 6.4%, 4.6% and 1.3% of the respective subset. At T0, significantly less donor NK cells were detected in recipients of OCS lungs (p<0.008), while T cells were reduced non-significantly. No correlation between donor NK or T cell frequencies was observed for CIT or PGD. In the limited number of patients at risk, a trend towards higher early donor T cell frequencies in recipients not developing CLAD at two years after Tx was observed (p=0.04). Donor T and NK cells are detectable in blood of all lung recipients during the first 3 weeks after Tx and did not correlate with CIT or PGD. Preservation with portable EVLP resulted in decreased NK cell frequencies which might be explained by their ex vivo mobilization. Furthermore, transient donor chimerism might have a protective effect against CLAD development.