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Leslie Baruch Brent 1925 - 2019

The BSI is saddened to learn about the recent death of our Honorary Member, Professor Leslie Baruch Brent. Leslie had been a member of the British Society for Immunology for over 60 years, making significant contributions to the field over decades.


Leslie (Lothar) Baruch Brent MBE {5 July 1925 (Köslin) – 21 December 2019 (London)} was co-author of ‘probably the most important paper in the history of transplantation’ published in Nature in 1953. Later the extended 1956 report, published in the Philosophical Transactions of the Royal Society , was regarded as one of the 17 most influential papers that had appeared during the journal’s 350-year history.

Brent’s key experiment, performed while a PhD student in the Department of Zoology at University College London (UCL), used white and brown inbred mice. Cells from one inbred (donor) strain were injected directly into immunologically immature late foetuses of a different (recipient) strain. Later skin grafts from mice of different strains were performed. Many grafts were accepted, but only if they were from the donor strain; grafts from mice of other strains were rejected. The resulting images were dramatic: white mice had patches of brown fur and brown mice had patches of white fur.

The story of this famous Billingham– Brent–Medawar work is renowned. How the charismatic polymath leader Medawar, together with his postdoctoral fellow Billingham (who had already begun his own distinguished independent immunological career) and a young Kindertransport refugee, created between them a remarkable intellectual environment in Zoology at UCL. They were termed the ‘Holy Trinity’, with Brent presumably the Son. They established a set of key facts which challenged and changed the way we recognise ourselves – and others. Medawar’s public recognition of his team immediately after the 1960 Nobel announcement, and much later the reflections that arose after release of the Nobel Committee’s related letters, highlighted this common effort. Notably the author order in the two main publications is alphabetical, but his colleagues arranged that Brent would give the first oral presentation. The UCL team acknowledged the contribution made previously by Ray Owen that fraternal calf twins show chimerism, which he postulated was caused by prenatal exposure to red cell precursors. They recognised and brought to the fore the concept of ‘tolerance’ and deduced that loss of tolerance could explain what was later termed autoimmunity.

Brent’s subsequent career took him to Southampton, as Professor of Zoology, and then to St Mary’s Hospital Medical School in Paddington, where he was Professor of Immunology for 21 years. He showed that tolerance can be induced in adults, studied graft versus host disease, and explored the immunoregulatory role of T lymphocytes. The concept that we can ‘tolerise’ using powerful immunosuppressive tools was an indirect product of his work. He developed a clinical service and led a Master’s programme in clinical immunology. He fostered research by his colleague Tony Pinching on HIV and AIDS. He championed the role of women in the medical school, despite the fact that St Mary’s was known for rugby as well as science. He was the first General Secretary of the British Transplantation Society, with Medawar as President. His History of Transplantation provides unique in-depth critical insight into the scientific background of the 1953 publication. It also acts as a personal memoir and shows eloquently his underlying honesty and fair play.

He showed that tolerance can be induced in adults, studied graft versus host disease, and explored the immunoregulatory role of T lymphocytes. The concept that we can ‘tolerise’ using powerful immunosuppressive tools was an indirect product of his work

Under normal circumstances this could suffice as a fitting tribute to one of the UK’s leading immunologists. However, there is another narrative, which is reflected in a different book, Sunday’s Child? A Memoir. This narrative is about an 11-year-old, forced to leave homes and school, living in an orphanage in Berlin. 

His combination of intellect and leadership must have played a role in the decision that he would cope with being one of the first Kindertransport children. He was placed first in Dovercourt. Later, at the progressive school, Bunce Court, he was inspired by the headmistress, Anna Essinger, not only academically but also by the help he (and others) received in learning how to form loving and caring relationships. His rapid mastery of English led to his becoming the public face of his peers, interviewed to promote their image and hence recruit more foster families. At 16 the charity sponsoring him ran out of money, and he started work as a chemistry laboratory assistant in Birmingham. He volunteered for the Royal Warwickshire Regiment and ended up in the British Army of the Rhine. On his return to the UK he studied Zoology, and his Professor, Peter Medawar, invited him to continue as a PhD student.

Meantime letters from his parents, Arthur and Charlotte, and his sister Eva, had ceased in 1942, and on a post-war visit to Berlin he was unable to trace them, apart from the fact that they had been ‘sent east’. Later he learned that in 1942 they had been transported to Riga in packed cattle trucks, taken into the woods and shot. He had ‘Stolpersteine’ – small brass plaques – set in the pavement outside their former Berlin home to commemorate them. He was active in the Association of Jewish Refugees, and a recent personal chance re-encounter with him in that context highlighted both his kindness and his meticulous intellect. In November 2018 he delivered his testimony and spoke from the pulpit at Westminster Abbey at a service to mark the 80th anniversary of Kristallnacht.

Today, meta-analysis, systems biology and biostatistics are seen as complementary to, if not replacements for, the imagination of open-minded, creative scientists and clinicians. However, as Elizabeth Simpson wrote in her review of the Medawar group, the latter often receive the clues that provide the vital insight(s) about novel approaches: Billingham, Brent and Medawar, and their closely associated colleagues, attest to this – they had a ‘hands-on’ approach, and were ever open to the challenge of the next experiment.

Although Brent was a secular Jew, he was aware that ‘baruch’ means blessed. Perhaps it is not too far off the mark to say that humanity has been blessed by his life’s work, and by his generosity of spirit; that his family were blessed by his insight and affection; and that he set a blessed example in turning away from unspeakable intolerance and personal loss, focusing instead upon the study of tolerance.

David R Katz
Emeritus Professor of Immunopathology
Division of Infection and Immunity
University College London