Medawar, Peter Brian WORLD OF MICROBIOLOGY AND IMMUNOLOGY370•
Medawar was born on February 28, 1915, in Rio de
Janeiro, Brazil, to Nicholas Medawar and the former Edith
Muriel Dowling. When he was a young boy, his family moved
to England, which he thereafter called home. Medawar
attended secondary school at Marlborough College, where he
first became interested in biology. The biology master encour-
aged Medawar to pursue the science under the tutelage of one
of his former students, John Young, at Magdalen College.
Medawar followed this advice and enrolled at Magdalen in
1932 as a zoology student.
Medawar earned his bachelor’s degree from Magdalen
in 1935, the same year he accepted an appointment as
Christopher Welch Scholar and Senior Demonstrator at
Magdalen College. He followed Young’s recommendation that
he work with pathologist Howard Florey, who was undertak-
ing a study of penicillin, work for which he would later
become well known. Medawar leaned toward experimental
embryology and tissue cultures. While at Magdalen, he met
and married a fellow zoology student. Medawar and his wife
had four children.
In 1938, Medawar, by examination, became a fellow of
Magdalen College and received the Edward Chapman
Research Prize. A year later, he received his master’s from
Oxford. When World War II broke out in Europe, the Medical
Research Council asked Medawar to concentrate his research
on tissue transplants, primarily skin grafts. While this took
him away from his initial research studies into embryology,
his work with the military would come to drive his future
research and eventually lead to a Nobel Prize.
During the war, Medawar developed a concentrated
form of fibrinogen, a component of the blood. This substance
acted as a glue to reattach severed nerves, and found a place in
the treatment of skin grafts and in other operations. More
importantly to Medawar’s future research, however, were his
studies at the Burns Unit of the Glasgow Royal Infirmary in
Scotland. His task was to determine why patients rejected
donor skin grafts. He observed that the rejection time for
donor grafts was noticeably longer for initial grafts, compared
to those grafts that were transplanted for a second time.
Medawar noted the similarity between this reaction and the
body’s reaction to an invading virus or bacteria. He formed the
opinion that the body’s rejection of skin grafts was immuno-
logical in nature; the body built up an immunityto the first
graft and then called on that already-built-up immunity to
quickly reject a second graft.
Upon his return from the Burns Unit to Oxford, he
began his studies of immunology in the laboratory. In 1944, he
became a senior research fellow of St. John’s College, Oxford,
and university demonstrator in zoology and comparative
anatomy. Although he qualified for and passed his examina-
tions for a doctorate in philosophy while at Oxford, Medawar
opted against accepting it because it would cost more than he
could afford. In his autobiography, Memoir of a Thinking
Radish,he wrote, “The degree served no useful purpose and
cost, I learned, as much as it cost in those days to have an
appendectomy. Having just had the latter as a matter of
urgency, I thought that to have both would border on self-
indulgence, so I remained a plain mister until I became aprof.” He continued as researcher at Oxford University
through 1947.
During that year Medawar accepted an appointment as
Mason professor of zoology at the University of Birmingham.
He brought with him one of his best graduate students at
Oxford, Rupert Everett “Bill” Billingham. Another graduate
student, Leslie Brent, soon joined them and the three began
what was to become a very productive collaboration that
spanned several years. Their research progressed through
Medawar’s appointment as dean of science, through his sev-
eral-month-long trip to the Rockefeller Institute in New York
in 1949—the same year he received the title of fellow from the
Royal Society—and even a relocation to another college. In
1951, Medawar accepted a position as Jodrell Professor of
Zoology and Comparative Anatomy at University College,
London. Billingham and Brent followed him.
Their most important discovery had its experimental
root in a promise Medawar made at the International Congress
of Genetics at Stockholm in 1948. He told another investiga-
tor, Hugh Donald, that he could formulate a foolproof method
for distinguishing identical from fraternal twin calves. He and
Billingham felt they could easily tell the twins apart by trans-
planting a skin graft from one twin to the other. They reasoned
that a calf of an identical pair would accept a skin graft from
its twin because the two originated from the same egg,
whereas a calf would reject a graft from its fraternal twin
because they came from two separate eggs. The results did not
bear this out, however. The calves accepted skin grafts from
their twins regardless of their status as identical or fraternal.
Puzzled, they repeated the experiment, but received the same
results.
They found their error when they became aware of work
done by Dr. Frank Macfarlane Burnetof the University of
Melbourne, and Ray D. Owen of the California Institute of
Technology. Owen found that blood transfuses between twin
calves, both fraternal and identical. Burnet believed that an
individual’s immunological framework developed before
birth, and felt Owen’s finding demonstrated this by showing
that the immune system tolerates those tissues that are made
known to it before a certain age. In other words, the body does
not recognize donated tissue as alien if it has had some expo-
sure to it at an early age. Burnet predicted that this immuno-
logical tolerance for non-native tissue could be reproduced in
a lab. Medawar, Billingham, and Brent set out to test Burnet’s
hypothesis.
The three-scientist team worked closely together, inoc-
ulating embryos from mice of one strain with tissue cells from
donor mice of another strain. When the mice had matured, the
trio grafted skin from the donor mice to the inoculated mice.
Normally, mice reject skin grafts from other mice, but the
inoculated mice in their experiment accepted the donor skin
grafts. They did not develop an immunological reaction. The
prenatal encounter had given the inoculated mice an acquired
immunological tolerance. They had proven Burnet’s hypothe-
sis. They published their findings in a 1953 article in Nature.
Although their research had no applications to transplants
among humans, it showed that transplants were possible.womi_M 5/7/03 7:52 AM Page 370