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PLoS One. 2014 Mar 21;9(3):e92888. doi: 10.1371/journal.pone.0092888. eCollection 2014.

Inhibition of calcineurin abrogates while inhibition of mTOR promotes regulatory T cell expansion and graft-versus-host disease protection by IL-2 in allogeneic bone marrow transplantation.

Author information

1
Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States of America; First Department of Internal Medicine, Kansai Medical University, Osaka, Japan.
2
Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
3
First Department of Internal Medicine, Kansai Medical University, Osaka, Japan.

Abstract

Regulatory T cells (Treg)s attenuate excessive immune responses, making their expansion beneficial in immune-mediated diseases including allogeneic bone marrow transplantation (BMT)-associated graft-versus-host disease (GVHD). We have recently reported that Treg expansion does not require phospholipase Cγ activation when IL-2 is provided. As such, the combination of IL-2 and a calcineurin inhibitor (Cyclosporine A; CsA) expands Tregs while inhibiting Tconv proliferation and protects against a mouse model of multiple sclerosis. However, CsA inhibits Treg proliferation in the presence of a TCR stimulus, suggesting that CsA may negatively impact Treg proliferation when they receive strong allogeneic MHC-mediated TCR signals. In this study, we show that CsA inhibits Treg proliferation and inducible Treg generation in allogeneic but not in syngeneic BMT when IL-2 is provided. In contrast to CsA, the mTOR inhibitor (Rapamycin) almost completely suppressed IL-2-mediated Treg proliferation. However, CsA and Rapamycin inhibited Treg proliferation to a similar extent when TCR stimulation was provided. Furthermore, Rapamycin promoted Treg expansion and inducible Treg generation in allogeneic BMT recipients treated with IL-2. Consistent with these observations, CsA abrogated while Rapamycin promoted the protective effect of IL-2 on allogeneic BMT-induced GVHD. These results suggest that while CsA permits IL-2-induced Treg proliferation in the syngeneic setting (absence of strong TCR signals), CsA in combination with IL-2 may be detrimental for Treg proliferation in an allogeneic setting. Thus, in allogeneic settings, an mTOR inhibitor such as Rapamycin is a better choice for adjunct therapy with IL-2 in expansion of Tregs and protection against allogeneic BMT-induced GVHD.

PMID:
24658577
PMCID:
PMC3962458
DOI:
10.1371/journal.pone.0092888
[Indexed for MEDLINE]
Free PMC Article

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