disclosed is a method of inhibiting a rejection response by a primate to a transplanted organ . one exposes the primate to a mutant diphtheria toxin linked to anti - cd3 antibody so as to largely eliminate the host &# 39 ; s peripheral blood t cell lymphocyte population . at the same time as , or after , the exposure step one administers to the primate &# 39 ; s thymus gland donor lymphocytes . transplantation of the organ follows . the primate is tolerized to the transplanted organ .