Memory T cells: how might they disrupt the induction of tolerance?

Clinical and experimental evidences suggest that alloreactive memory T cells may be part of the normal T-cell repertoire and that such cells are detrimental to the survival of foreign organ allografts induced by the administration of conventional immunosuppression or experimental tolerance-inducing therapies. The potential mechanisms by which alloreactive memory T cell may form a barrier to the induction of tolerance will be discussed.