The morbidity and mortality associated with chronic immunosuppression provide a strong
motivation for development of clinical tolerance. This paper discusses the definition (s) of
clinical (operational) tolerance, the role of chimerism in experimental and clinical tolerance,
and the special role of bone marrow in tolerance induction. The states of microchimerism
and macrochimerism are defined and related to certain clinical observations in solid organ
transplantation. Current clinical strategies already being tested in the clinic are briefly …