Transplantation Tolerance

Fifty years have passed since the seminal contribution of Billingham, Brent and Medawar in Nature entitled Actively Acquired Tole­rance of Foreign Cells [1] that paved the way for what is now commonly referred to as transplantation tolerance. Often called the Holy Grail of transplant medicine, the pheno­menon has been as elusive to researchers, at least in the clinical setting, as it is intriguing. Although the major barriers preventing the translation of experimental tolerance strategies to the clinic remain immunologic in nature, as the concept approaches clinical reality, various safety and ethical concerns become increas­ingly important. The field of renal transplanta­tion has enjoyed recent dramatic pharmacologic­related improvements in acute rejection and short-term graft survival rates, [2] which raises the standard for any clinical tolerance trial and has even caused some to question the very need for clinical tolerance.