Regulatory T cells Exhibit Decreased Proliferation but Enhanced Suppression After Pulsing with Sirolimus

• Type of Material: Article
• Authors: Karnail Singh, Emory University; Natalia Kozyr, Emory University; Linda Stempora, Emory University; Allan D Kirk, Emory University; Christian P Larsen, Emory University; Bruce R. Blazar, University of Minnesota; Leslie S. Kean, Emory University
• Language: English
• Date: 2012-06
• Publisher: Wiley: 12 months
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2012 The American Society of Transplantation and the American Society of Transplant Surgeons
• Final Published Version (URL): http://onlinelibrary.wiley.com/doi/10.1111/j.1600-6143.2011.03963.x/abstract;jsessionid=518A812BDFA574741E700A19C16DB0BD.d04t01
• Title of Journal or Parent Work: American Journal of Transplantation
• ISSN: 1600-6135
• Volume: 12
• Issue: 6
• Start Page: 1441
• End Page: 1457
• Grant/Funding Information: This work was supported by Yerkes National Primate Research Center Base Grant, #RR00165. CPL was supported by NIH grant #s 2U19 AI051731, and 2P01 AI044644. LSK was supported by grant #s 5K08 AI065822, 2U19 AI051731, 1R01 HL095791 and 2U24 RR018109, and by a Burroughs Wellcome Fund Career Award in the Biomedical Sciences. ADK was supported by JDRF 1-2008-594, 1U01AI079223-01A1, 5 U19 AI051731. BRB was supported by NIH R01 AI34495, HL 56067, and P01 CA 067493.
• Keywords: sirolimus; immunosuppression; regulatory T cells
• Research Categories: Health Sciences, Medicine and Surgery

Abstract

Although regulatory T cells (Tregs) suppress allo-immunity, difficulties in their large-scale production and in maintaining their suppressive function after expansion have thus far limited their clinical applicability. Here we have used our non-human primate model to demonstrate that significant ex vivo Treg expansion with potent suppressive capacity can be achieved and that Treg suppressive capacity can be further enhanced by their exposure to a short pulse of sirolimus. Both unpulsed and Sirolimus-Pulsed Tregs (SPTs) are capable of inhibiting proliferation of multiple T cell subpopulations, including CD4+ and CD8+T cells, as well as antigen-experienced CD28+CD95+ memory and CD28−CD95+ effector subpopulations. We further show that Tregs can be combined in vitro with CTLA4-Ig (belatacept) to lead to enhanced inhibition of allo-proliferation. SPTs undergo less proliferation in a mixed lymphocyte reaction (MLR) when compared with unpulsed Tregs, suggesting that Treg-mediated suppression may be inversely related to their proliferative capacity. SPTs also display increased expression of CD25 and CTLA4, implicating signaling through these molecules in their enhanced function. Our results suggest that the creation of SPTs may provide a novel avenue to enhance Treg-based suppression of allo-immunity, in a manner amenable to large-scale ex vivo expansion and combinatorial therapy with novel, costimulation-blockade-based immunosuppression strategies.