Ex Vivo-Expanded Non-Human Primate Regulatory T Cells Are Resistant to Alemtuzumab-Mediated, Complement-Dependent Cytotoxicity
Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA
Cardiothoracic Surgery, University of Pittsburgh, Pittsburgh, PA
Surgery, Erasmus Medical Center Rotterdam, Rotterdam, Netherlands
Immunology, University of Pittsburgh, Pittsburgh, PA
Meeting: 2013 American Transplant Congress
Abstract number: B1127
Background: Alemtuzumab (Campath-1H) is a humanized mAb directed against CD52 that is expressed on all lymphocytes, including CD4+FoxP3+ regulatory T cells (Treg), and that depletes lymphocytes and other leukocytes, mainly by complement-dependent mechanisms.
Methods: We investigated the influence of alemtuzumab on (i) ex vivo-expanded naturally-occurring Treg (nTreg) that could potentially be used in adoptive cell therapy of allograft rejection, and (ii) nTreg following infusion of alemtuzumab in Indonesian cynomolgus monkeys. (i) Treg were flow-sorted from PBMC and lymph nodes and expanded for two rounds using anti-CD3/CD28 beads, IL-2 and TGF-Β. CD52 expression, binding of alemtuzumab, and killing of cells were compared between freshly-isolated and expanded Treg and effector T cells. (ii) Monkeys undergoing allogeneic heart transplantation received 3 doses of alemtuzumab and were monitored for Treg and serum alemtuzumab levels.
Results: (i) ex vivo-expanded nTreg were characterized by CD25hi/CD127low and FoxP3+ expression and suppressive capacity by CFSE-MLR. Expanded Treg exhibited progressive downregulation of CD52 expression, no change in CD46 (complement inhibitory factor) expression, absence of alemtuzumab binding and no complement-dependent killing. (ii) In vivo infusion of alemtuzumab resulted in potent depletion of all lymphocytes, but a transient increase in the proportion of circulating Treg. After infusion of alemtuzumab, monkey serum killed fresh PBMC, but not expanded Treg.
Conclusions: Expanded cynomolgus monkey nTreg are resistant to alemtuzumab-mediated, complement-dependent cytotoxicity. Our in vitro data suggest that expanded nTreg can be infused into graft recipients given alemtuzumab without complement-mediated killing. Furthermore, our in vivo data show that alemtuzumab infusion results in transient relative increase in circulating Treg.
To cite this abstract in AMA style:
Dons E, Raimondi G, Zhang H, Bhama J, Tu L, Ezzelarab M, IJzermans J, Cooper D, Thomson A. Ex Vivo-Expanded Non-Human Primate Regulatory T Cells Are Resistant to Alemtuzumab-Mediated, Complement-Dependent Cytotoxicity [abstract]. Am J Transplant. 2013; 13 (suppl 5). https://atcmeetingabstracts.com/abstract/ex-vivo-expanded-non-human-primate-regulatory-t-cells-are-resistant-to-alemtuzumab-mediated-complement-dependent-cytotoxicity/. Accessed October 6, 2024.« Back to 2013 American Transplant Congress