Here, we present evidence that TCR diversity is an essential aspect of Foxp3+ Treg-cell homeostasis and function. Treg cells with a broader TCR repertoire exhibited sustained survival and expansion in hosts with less diverse Treg cells, which likely reflected their advantage in competition for self peptides and other peptides presented

by MHC class II. Adoptive transfer experiments revealed that the TCR repertoire of Treg-cell populations varied by anatomical location. Functionally, our data strongly suggest that see more TCR diversity is a critical factor for efficient Treg-cell mediated suppression of experimental acute GvHD. If not crossed to a Rag-deficient background, TCR-Tg mice contain functional Treg cells that develop through thymic selection of endogenous, non-clonotypic TCR rearrangements 14, 39, 40. Only in rare exceptions, e.g. in AND- or HA- TCR-Tg mice 41, 42, a limited number of clonotypic thymocytes was shown to develop into Foxp3+ Treg

cells 15, 16, 43. Here, the use of broadly available OT-II TCR-Tg as Treg-cell recipients allowed efficient in vivo expansion of adoptively transferred WT Treg cells with a broader TCR repertoire. Moreover, congenic markers in combination with the eGFP-reporter in the Foxp3 locus assured unambiguous detection of Treg cells after adoptive transfer. To the best of our knowledge, Selleckchem HDAC inhibitor such a robust expansion of adoptively transferred ADP ribosylation factor Treg cells as described here is unprecedented in non-lymphopenic mice. Several studies in humans and mice have implied that TCR diversity is an important feature of Treg cells. A comprehensive study on one single human T-cell repertoire recently concluded that Treg cells were the most diverse T cells 28. The

authors predicted 89 920 TCRα CDR3 sequences in Treg cells (defined as CD4+CD25+) compared with 58 325 in all other naive and transitional CD45RA+ non-Treg cells. This is in line with former data obtained by spectratyping of human Treg-cell CDR3 regions 44, 45. Furthermore, earlier studies using classical sequencing approaches also found at least similar diversity in mouse Treg cells 6, 7. Our study demonstrated that the TCR repertoire of WT mouse Treg cells was indeed very broad, however, at least TCR-Vα8 CDR3 diversity was found to be even higher in WT Foxp3−CD4+ T cells than in Treg cells (Supporting Information Fig. 2). Recent studies suggested that thymic intra- and interclonal competition for limited antigen presented on MHC class II may be an important mechanism to generate Treg cells with a broad TCR spectrum 15, 16, 46. This was specific for natural Treg cells but not for Foxp3−CD4+ T cells and thus led to the conclusion that TCRs from Treg cells may on average have higher affinity for self-peptide-MHC.