Prevention of heart allograft rejection by immunotherapy with ex vivo-expanded Foxp3+CD4+CD25+ natural regulatory T cells

Guliang Xia*, Zheng Jenny Zhang, Bryon D. Johnson

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

The role of Foxp3+CD4+CD25+ regulatory T (Treg) cells has increasingly been demonstrated in modulating allograft rejection and mediating allograft tolerance in rodents. In humans, a favorable transplantation outcome is frequently associated with increased frequencies of Foxp3+CD4+CD25+ Treg cells. Over the past several years, we have been interested in using natural CD4+CD25+ Treg (nTreg) as cellular therapy to prevent heart allograft rejection in mice. Due to low frequencies in fresh tissues, ex vivo expansion is essential for generating sufficient numbers of CD4+CD25+ nTreg cells to target the large repertoire of alloreactive effector T (Teff) cells in transplant recipients. Strategies for ex vivo expansion have evolved from alloantigen (alloAg)-nonspecific (e.g., anti-CD3/CD28 mAb-coated beads) approaches to alloAg-specific (e.g., live donor bone marrow-derived dendritic cells [BM-DC]) methods, with reasonable cell expansion after 20 days of culture. An unexpected observation was a gradual decrease of the transcription factor Foxp3, a critical regulator for suppressive function during ex vivo expansion, when in vitro cultures were supplemented with only interleukin (IL)-2. We systemically examined the kinetics of Foxp3 expression in CD4+CD25+ and CD4+Foxp3+ nTreg cells (FACS-sorted from Foxp3-green fluorescence protein [GFP] knock-in mice) during ex vivo expansion, and confirmed the activation of T cell receptors (TCR), leading to the loss of Foxp3 from the original Foxp3+ precursors. We have made significant progress towards preserving Foxp3 expression by modifying expansion protocols to include transforming growth factor (TGF)-β, all-trans retinoic acid (RA), histone deacetylase inhibitor trichostatin A (TSA), or combinations of these reagents. Importantly, fresh CD4+CD25+ nTreg cells expanded by the "modified" culture conditions (e.g., RA/TSA/TGF-β/IL-2) not only expressed high Foxp3 in vitro (∼45%) but also retained high Foxp3 expression in vivo (∼91%) during prevention of heart allograft rejection. As a result, long-term survival of fully major histocompatibility complex (MHC)-mismatched heart allografts was successfully achieved in wild-type mice without using conventional immunosuppressants. Further optimization of protocols for expanding CD4+CD25+ nTreg cells ex vivo may be essential for the successful use of these cells in preventing heart allograft rejection in immune competent mice.

Original languageEnglish (US)
Title of host publicationHeart Transplantation
Subtitle of host publicationIndications and Contradictions, Procedures and Complications
PublisherNova Science Publishers, Inc.
Pages25-49
Number of pages25
ISBN (Electronic)9781608765911
ISBN (Print)9781607412281
StatePublished - Jan 1 2009

ASJC Scopus subject areas

  • Medicine(all)

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    Xia, G., Zhang, Z. J., & Johnson, B. D. (2009). Prevention of heart allograft rejection by immunotherapy with ex vivo-expanded Foxp3+CD4+CD25+ natural regulatory T cells. In Heart Transplantation: Indications and Contradictions, Procedures and Complications (pp. 25-49). Nova Science Publishers, Inc..