Generation of Regulatory Dendritic Cells From Living Donor Liver Transplant Perfusates

Safety and immunological activity of donor blood monocyte-derived regulatory dendritic cells (DCreg) generated ex vivo have been demonstrated recently in living donor liver transplantation. A potential alternative/additional source of DCreg precursors is the allograft perfusion fluid. Our goal was to establish the extent to which DCreg could be generated from CD14 + myeloid precursors in living donor liver perfusate (LD-LP) and to assess the phenotype and immunoregulatory properties of the perfusate-derived DCreg (LP-DCreg).

Presumptive DCreg were generated from CD14 + precursors recovered from n = 14 right lobe liver grafts using GM-CSF + Interleukin (IL)-4, with the addition of vitamin D3 and IL-10. Control immature DC and corresponding Toll-like receptor 4 agonist monophosphoryl lipid A (MPLA)-stimulated DC populations were also generated. Cell phenotype and function, DCreg maturation resistance, T-cell allostimulatory activity, and the roles of immunoregulatory molecules in llograft perfusate (LP)-DCreg function were analyzed by flow cytometry, RT-PCR analysis, cytokine assays, and MLR.

Presumptive DCreg generated from live donor-LP comprised relatively high proportions of CD141 hi CD163 + cells. They expressed comparatively high coinhibitory programmed death ligand-1 (PD-L1):costimulatory molecule (CD86) ratios, even after MPLA stimulation. Moreover, unlike immature DC, they produced high levels of IL-10 but minimal/low proinflammatory IL-12 and tumor necrosis factor alpha following MPLA stimulation. These LP-DCreg were poor stimulators of naïve allogeneic T cells and suppressed alloreactive CD4 and CD8 T-cell proliferation. Blocking of the PD-L1-PD-1 signaling pathway reversed their regulatory function.

Liver graft perfusate constitutes a novel source of myeloid precursors for DCreg generation.