Objective Self-tolerance is a key feature of the immune system; its failure causes autoimmune diseases such as Multiple Sclerosis or Type-1-Diabetes. Remarkably, T cell tolerance operates via two fundamentally different mechanisms: potentially dangerous cells are either eliminated (clonal deletion) or re-programmed to differentiate into regulatory T (Treg) cells (clonal diversion). Paradoxically, both tolerance modes can ensue from self-antigen-encounter in the thymus, and the parameters specifying these opposing cell-fates remain poorly understood. Moreover, the relative contribution of clonal deletion versus clonal diversion to tolerance at the level of diverse immune cell repertoires has not been determined. In particular, the paucity of antigen-specific cells is a major experimental obstacle to unravelling to what extent cells with shared autoreactive specificity, yet different T cell receptors (TCRs), are subject to either mode of tolerance.Breakthroughs in visualizing minute cohorts of antigen-specific cells, characterizing the TCRs on individual cells and large-scale TCR sequencing now provide a unique opportunity to tackle these challenging questions. Based upon my expertise in thymus biology and T cell selection, I will exploit these technological advances to reveal where and how tolerance either generates ‘holes’ in the repertoire or diverts cells into a ‘benign’ sub-repertoire. The main objectives are (i) to identify and classify deleted or diverted TCR-entities through comparing ‘uncensored’ and ‘censored’ repertoires in the absence or presence of a disease-relevant autoantigen and (ii) to identify TCR intrinsic features as well as T cell extrinsic determinants that specify clonal deletion versus clonal diversion.The proposed research elucidates a fundamental aspect of vertebrate immunology, but also has major implications regarding the therapeutic promise of harnessing endogenous, antigen-specific Treg cells in autoimmunity. Fields of science medical and health sciencesbasic medicineneurologymultiple sclerosismedical and health sciencesbasic medicineimmunologyautoimmune diseases Keywords T cell tolerance T cell repertoire Thymus Clonal deletion Regulatory T cell Programme(s) H2020-EU.1.1. - EXCELLENT SCIENCE - European Research Council (ERC) Main Programme Topic(s) ERC-2016-ADG - ERC Advanced Grant Call for proposal ERC-2016-ADG See other projects for this call Funding Scheme ERC-ADG - Advanced Grant Host institution LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN Net EU contribution € 2 414 500,00 Address GESCHWISTER SCHOLL PLATZ 1 80539 Muenchen Germany See on map Region Bayern Oberbayern München, Kreisfreie Stadt Activity type Higher or Secondary Education Establishments Links Contact the organisation Opens in new window Website Opens in new window Participation in EU R&I programmes Opens in new window HORIZON collaboration network Opens in new window Total cost € 2 414 500,00 Beneficiaries (1) Sort alphabetically Sort by Net EU contribution Expand all Collapse all LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN Germany Net EU contribution € 2 414 500,00 Address GESCHWISTER SCHOLL PLATZ 1 80539 Muenchen See on map Region Bayern Oberbayern München, Kreisfreie Stadt Activity type Higher or Secondary Education Establishments Links Contact the organisation Opens in new window Website Opens in new window Participation in EU R&I programmes Opens in new window HORIZON collaboration network Opens in new window Total cost € 2 414 500,00