At Oxford during World War II, Peter Medawar and his colleagues made the remarkable observation that patients pre-treated in early life with embryotic cells did not reject skin grafts from unrelated donors. This gave rise to the concept of acquired immunological tolerance and revolutionized the field of organ transplantation as well as changed our understanding of how the immune system functions.
Before Medawar’s work, the prevailing belief was that the immune system’s ability to distinguish between “self” and “non-self” was fixed at birth. This posed a significant obstacle to organ transplantation, as it suggested that the body would always reject foreign tissue.
Peter Medawar was born in 1915 in Brazil to a Lebanese father and a British mother who moved to England when he was two. He attended Marlborough College and later Magdalen College, Oxford, where he came under the influence of biologists such as Sir Howard Florey and Sir Charles Sherrington and where he obtained a bachelor’s degree in zoology in 1935 and a doctorate in 1941. He began his research career during World War II, working on skin grafts for burn victims. In 1949, along with colleagues Rupert Billingham and Leslie Brent, he began a series of experiments on mice, injecting cells from one strain into embryos or newborns of another strain. They found that when these mice grew to adulthood, they would accept skin grafts from the donor strain without rejection.
In 1953, Medawar, Billingham, and Brent published their seminal paper “Actively Acquired Tolerance of Foreign Cells” in Nature. This paper laid out the evidence for acquired immune tolerance and demonstrated that the immune system could learn to tolerate foreign antigens if exposed to them early in life. In 1960, this work earned Medawar the Nobel Prize in Physiology or Medicine, which he shared with Sir Frank Macfarlane Burnet, who had theoretically predicted the possibility of acquired tolerance. These findings opened the era of organ transplantation and the development of immunosuppressive drugs, as well as providing insights into the etiology and treatment of what came to be called autoimmune diseases, such as lupus and various forms of arteritis.
Peter Medawar also had a keen interest in the philosophy of science and was an ardent defender of the scientific method as a rigorous process based on experimentation and evidence. He became a popular essayist and wrote books such as The Art of the Soluble (1967) to educate the public about science. He was knighted in 1965 and appointed to the Order of Merit in 1981. In London in the early 1960s, I had planned to listen to his lecture when, just as he was about to enter the room, a young woman in the audience fainted. I must have been the only medical person in the audience, for I spent the next hour ministering to the lady and thus missed the opportunity to listen to one of the most important biologists of the 20th century.
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