Human thymic T cell repertoire is imprinted with strong convergence to shared sequences

•In thymus the TCRα repertoire is more diverse than the TCRβ repertoire and contains more nonproductive clonotypes.•A high proportion of thymic TCRs is shared between unrelated individuals and the sharing is much more marked in TCRα than in TCRβ repertoire.•The origin of shared repertoire seems to be due to both convergent rearrangement and thymic selection.