Discovery of Acquired Immunological Tolerance

British zoologist Peter Medawar, working with Rupert Billingham and Leslie Brent, demonstrated in 1953 that mice exposed as embryos or newborns to cells from a genetically different mouse strain would, once grown, accept skin grafts from that same strain without rejecting them, a phenomenon the team named actively acquired tolerance in a fuller 1956 paper. The finding experimentally confirmed a hypothesis Australian immunologist Frank Macfarlane Burnet had proposed in 1949, that the immune system could be trained during early development to recognize certain foreign tissue as its own rather than as a threat to be attacked. Medawar and Burnet shared the 1960 Nobel Prize in Physiology or Medicine for the discovery, which supplied the immunological foundation later organ transplantation depended on, including the understanding of graft rejection that made surgeon Joseph Murray's first successful human kidney transplant possible the following decade.