There is strong evidence that immunological self tolerance critically relies on the elimination of potentially autoaggressive T lymphocyte clones from the emerging immune repertoire during intrathymic T cell differentiation. These ‘forbidden’ T cells are deleted as a result of a confrontation with their specific self antigen as presented on medullary stroma cells. But this purging mechanism is remarkably leaky, allowing numerous autoreactive T cells to join the healthy immune repertoire. A paper in this issue of the European Journal of Immunology studies the effect of organ‐specific autoantigen expression on the cognate T cell repertoire. Myelin oligodendrocyte glycoprotein (MOG), a putative autoantigen in human multiple sclerosis, is used as a model self antigen. T cell receptor profiles in wild‐type mice were compared with those in MOG‐knock‐out mice. Surprisingly, significant differences were not found suggesting that, in this particular case, autoantigen expression does not affect the autoreactive T cell repertoire.

See accompanying article: http://dx.doi.org/10.1002/eji.200535021