We have previously demonstrated that the endothelial cells located in immune-privilege sites, such as livers, suppress T-cells in response to both of direct and indirect allo-recognition through programmed death (PD) 1/PD-L1 pathway in mice and humans. In this study, we have proven that endothelial-like cells expressing PD-L1 can be transdifferentiated from human peripheral blood monocytes. Human LSECs were isolated from the disaggregated liver tissues obtained from patients undergoing surgical resection of colorectal liver metastasis. Human CD14⁺ cells were isolated from peripheral blood by using magnetic sorting and cultured in EGM2 medium supplemented with GM-CSF, IL-4, VEGF, hFGF-B, R3-IGF-1 and LPS for 14 days. Naïve human LSECs constitutively express molecules necessary for antigen presentation, i.e., MHC-class II, CD40, CD80, and CD86 together with PD-L1. The transdifferentiated cells morphologically appeared endothelial-like cells and phenotypically resembled LSECs, i.e., they were MHC-class II⁺, CD40^low, CD80^low, CD86^low, CD105⁺, PDL-1⁺. The suppressive activity of those cells on allogeneic T cells was analyzed by a MLR assay using CFSE labeling technique. Allo-immune responses of both of CD4⁺ and CD8⁺ T cells in the MLR assays were suppressed by subsequently adding the stimulator-type endothelial-like cells, whereas there were not suppressed in response to anti-third party stimuli. The PD-1 expression on allo-reactive T cells among the final products of the MLR assays was elevated over time during culture. These findings raise a novel concept to induce hyporesponsiveness of alloreactive T cells by inoculating donor-derived those cells even in transplantation of organs other than liver.

CITATION INFORMATION: Tanaka Y., Ohdan H. Human Endothelial-Like Cells Transdifferentiated from Peripheral CD14⁺ Monocytes Inhibit T Cells in Response to Allo-Stimulation Am J Transplant. 2017;17 (suppl 3).

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