Published online before print August 7, 2007
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Kings College London, MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
2 Correspondence: Department of Asthma, Allergy, and Respiratory Science, Kings College London, 5th Floor Thomas Guy House, Guys Hospital Campus, London SE1 9RT, UK. E-mail: alistair.noble{at}kcl.ac.uk
ABSTRACT
CD4+CD25+ regulatory T cells (Tregs) are well known to suppress immunopathology induced in lymphopenic animals following T cell reconstitution, including acute graft-versus-host disease (GVHD) post-bone marrow transplantation. The regulatory potential of this subset in nonlymphopenic hosts and in chronic, Th2-mediated GVHD is less clear. We have generated alloantigen-specific cells from CD4+CD25+ populations stimulated with MHC-disparate dendritic cells and found them to express a stable Treg forkhead box p3+ phenotype with enhanced suppressive activity mediated by cell contact. When transferred into nonlymphopenic F1 hosts, nonspecific Tregs proliferated as rapidly as CD4+CD25– cells but displayed distinct growth kinetics in vitro. Tregs, expanded in response to alloantigen in vitro, displayed greatly enhanced suppressive activity, which was partially antigen-specific. They were effective inhibitors of chronic GVHD, blocking donor cell engraftment, splenomegaly, autoantibody production, and glomerulonephritis. CD25+ and CD25– cells were equally susceptible to inhibition by immunosuppressive drugs targeting TCR signaling and rapamycin, but Tregs were resistant to inhibition by dexamethasone. The data indicate that alloantigen-driven expansion, rather than homeostatic proliferation, is key to the effectiveness of CD4+CD25+ Tregs in GVHD and suggest that cellular therapy with alloantigen-induced Tregs in combination with glucocorticoid treatment would be effective in prevention of chronic GVHD after immune reconstitution.
Key Words: alloreactivity suppression dexamethasone
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