Rapamycin-treated human endothelial cells preferentially activate allogeneic regulatory T cells
Chen Wang, Tai Yi, Lingfeng Qin, Roberto A. Maldonado, Ulrich H. von Andrian, Sanjay Kulkarni, George Tellides, Jordan S. Pober
Chen Wang, Tai Yi, Lingfeng Qin, Roberto A. Maldonado, Ulrich H. von Andrian, Sanjay Kulkarni, George Tellides, Jordan S. Pober
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Research Article Immunology

Rapamycin-treated human endothelial cells preferentially activate allogeneic regulatory T cells

Abstract

Human graft endothelial cells (ECs) can act as antigen-presenting cells to initiate allograft rejection by host memory T cells. Rapamycin, an mTOR inhibitor used clinically to suppress T cell responses, also acts on DCs, rendering them tolerogenic. Here, we report the effects of rapamycin on EC alloimmunogenicity. Compared with mock-treated cells, rapamycin-pretreated human ECs (rapa-ECs) stimulated less proliferation and cytokine secretion from allogeneic CD4+ memory cells, an effect mimicked by shRNA knockdown of mTOR or raptor in ECs. The effects of rapamycin persisted for several days and were linked to upregulation of the inhibitory molecules PD-L1 and PD-L2 on rapa-ECs. Additionally, rapa-ECs produced lower levels of the inflammatory cytokine IL-6. CD4+ memory cells activated by allogeneic rapa-ECs became hyporesponsive to restimulation in an alloantigen-specific manner and contained higher percentages of suppressive CD4+CD25hiCD127loFoxP3+ cells that did not produce effector cytokines. In a human-mouse chimeric model of allograft rejection, rapamycin pretreatment of human arterial allografts increased graft EC expression of PD-L1 and PD-L2 and reduced subsequent infiltration of allogeneic effector T cells into the artery intima and intimal expansion. Preoperative conditioning of allograft ECs with rapamycin could potentially reduce immune-mediated rejection.

Authors

Chen Wang, Tai Yi, Lingfeng Qin, Roberto A. Maldonado, Ulrich H. von Andrian, Sanjay Kulkarni, George Tellides, Jordan S. Pober

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Figure 9

PD-1 ligands protect rapamycin-pretreated grafts from T cell–mediated graft injury in vivo.

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PD-1 ligands protect rapamycin-pretreated grafts from T cell–mediated gr...
(A) Human artery interposition grafts were pretreated with vehicle or rapamycin and then re-transplanted into PBMC-reconstituted hosts and harvested after 10 days. Representative immunofluorescence detection of PD-L1 and PD-L2 on graft ECs is shown. ECs are stained with Ulex and visualized in green; PD-L1 and PD-L2 are visualized in red. Quantification of PD-L1 and PD-L2 immunofluorescence is normalized to staining in vehicle-pretreated grafts. Original magnification, ×200. (B) Rapamycin-pretreated grafts were transplanted into PBMC-reconstituted mice and subsequently treated with neutralizing PD-1 F(ab′)2 or control F(ab′)2 fragments. Grafts were harvested after 2 weeks and stained with EVG. Original magnification, ×100. (C) Representative immunofluorescence detection of infiltrating CD3+ T cells in grafts treated as in B. ECs are stained with Ulex and visualized in green; CD3+ cells are visualized in red. Intimal T cells were counted. Original magnification, ×200. Mean ± SEM are shown for A–C (n = 4 per group). *P < 0.05.