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This article is part of the supplement: Kitasato Symposium 2011: Translational prospects for cytokines in 2011

Oral presentation

Inducing a tolerogenic microenvironment within tissues

Stephen P Cobbold

Author Affiliations

Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, UK

Arthritis Research & Therapy 2011, 13(Suppl 2):O2  doi:10.1186/ar3406

The electronic version of this article is the complete one and can be found online at: http://arthritis-research.com/content/13/S2/O2


Published:16 September 2011

© 2011 Cobbold.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Oral presentation

The maintenance of tolerance to both self tissues foreign organ grafts depends on the activity of foxp3+ regulatory T cells (Treg). We have used MHC-matched skin grafts as a model system to study how such Treg can be induced therapeutically and the mechanisms by which they act. Using monospecific TCR transgenic mice we have shown that a short treatment with monoclonal antibodies that block full T cell activation in vivo allows the targeted tissue to itself induce de novo, antigen specific, foxp3+ Treg (iTreg) [1]. We also show that these iTreg are not only concentrated within the target tissue, but are continuously required to suppress the activity of primed effector cells also present within the tissue [2]. When taken together with previous findings of linked suppression and infectious tolerance [3], the evidence suggests that tolerance maintained by iTreg is dependent on a local, tolerogenic microenviroment within the tissue. One component of this microenvironment is the induction, by both innate inflammation and iTreg, of multiple enzymes that consume essential amino acids, including tryptophan, arginine and valine. Local amino acid depletion can be sensed by naïve and effector T cells, via the mammalian target of the immunosuppressive drug rapamycin (mTOR) pathway, which can synergise with TGFβ for the further induction of foxp3+ iTreg [4]. TGFβ is also able to up-regulate the ectoenzymes CD39 and CD73 both on T cells and antigen presenting cells to catabolise inflammatory ATP to anti-inflammatory adenosine [5]. Microarray analysis of tolerated and control skin grafts for patterns of gene expression associated with the tolerogenic microenvironment confirms that these mechanisms are preferentially active locally within the tolerated tissues rather than throughout the systemic lymphoid system. Of particular interest, these same mechanisms seem to be active in grafted syngeneic tissues [6], suggesting that iTreg maintained microenvironments are important for maintaining self tolerance in the face of an inflammatory insult. The challenge now is how we can exploit appropriate combinations of T cell blockade, mTOR inhibition and TGFβ activation for translation to the clinic.

References

  1. Cobbold SP, Castejon R, Adams E, Zelenika D, Graca L, Humm S, Waldmann H: Induction of foxp3+ regulatory T cells in the periphery of T cell receptor transgenic mice tolerized to transplants.

    J Immunol 2004, 172:6003-6010. PubMed Abstract | Publisher Full Text OpenURL

  2. Kendal AR, Chen Y, Regateiro F, Ma J, Adams E, Cobbold SP, Hori S, Waldmann H: Sustained vigilance of Foxp3+ T cells is vital for infectious tolerance in vivo.

    J Exp Med 2011, in press. OpenURL

  3. Cobbold SP, Adams E, Nolan KF, Regateiro FS, Waldmann H: Connecting the mechanisms of T cell regulation: dendritic cells as the missing link.

    Immunological Reviews 2010, 236:203-218. PubMed Abstract | Publisher Full Text OpenURL

  4. Cobbold SP, Adams E, Farquhar CA, Nolan KF, Howie D, Lui KO, Fairchild PJ, Mellor AL, Ron D, Waldmann H: Infectious tolerance via the consumption of essential amino acids and mTOR signaling.

    Proc Natl Acad Sci USA 2009, 106(29):12055-60. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  5. Regateiro FS, Howie D, Agorogiannis EI, Greaves DR, Cobbold SP, Waldmann H: CD73 expression and adenosine generation are controlled by TGF-β and modulated by inflammatory cytokines.

    Eur J Immunol 2011, in press. OpenURL

  6. Cobbold SP, Adams E, Waldmann H: Biomarkers of transplantation tolerance: more hopeful than helpful?

    Front Immun 2011, 2:9.

    p. 1-8. doi:10.3389/fimmu.2011.00009

    OpenURL