He fled Germany on the Kindertransport as a child before the outbreak of the Second World War, and grew up to become a celebrated immunologist and zoologist. Professor Leslie Baruch Brent, who has died aged 94, was part of that first fateful Kindertransport of children from a Berlin orphanage on December 2, 1938.

His breakthrough came in 1952 when, as a PhD student at Kings College, London, he co-authored the first of two ground-breaking papers with senior colleagues Professor Peter Medawar, the team leader, and Rupert Billingham, a post-doctoral researcher.The papers showed that immunological tolerance — the capacity to accept an unrelated tissue transplant — could be experimentally induced. The findings won acclaim for all three.

While it is now taken for granted that tissues and organs can be transplanted in genetically dissimilar recipients, this was a complete breakthrough in the early 50s. In fact it was considered so exceptional that the three were nicknamed The Holy Trinity by American immunologists. Armed with a doctorate in zoology at Birmingham University, Brent’s research now destined him to become a leading immunologist.

In the 40s Melaware himself proved that foreign tissues were rapidly broken down and destroyed by the same immune system that fights infection. Previous observations based on work on twin calves by the American immunogeneticist Ray Owen inspired the three to embark on their experiments. Owen discovered that precursor red cells in the calves must have been exchanged before birth, that the foreign cells had been accepted and therefore established their own lineage.

The three scientists took his discoveries further and exchanged skin grafts between fraternal calves.The grafts were largely accepted, indicating that some tolerance must have been established in foetal life.

They went on to prove this tolerance by experimenting on white and brown inbred mice. Brent’s two senior colleagues invited him to give the first talk on their work. He addressed a packed meeting of the Society for Experimental Biology, whose members were astonished at the findings, which were later published in the journal Nature. It was the same year that the journal published Watson and Crick’s paper on the discovery of the structure of DNA. Medaware received the Nobel Prize in 1960 in conjunction with Australian immunologist Frank Macfarlane Burnet and generously shared his prize money with Brent and Billingham, publicly insisting that this was not a gift but that “it comes to you as of right.”

Brent was born Lothar Baruch in Köslin, Germany, now part of Poland. Brought up in an observant home, he was the son of Charlotte and Arthur, a childrenswear sales rep, and recipient of the Iron Cross in the first World War. He had a sister, Eva. Forced to leave his school at the age of 11 because of official antisemitism, he was sent to the Jewish Orphanage in Pankow, Berlin. With his close, protective family background, Brent found it hard to adjust. He would later describe his orphanage years as one of his most traumatic experiences. And yet they saved his life. The director of the orphanage arranged for him to leave Germany on the first Kindertransport three weeks after Kristallnacht, and he arrived at Dovercourt, a converted holiday camp on December 2, 1938.

He spent three weeks in the camp before going to Bunce Court, a progressive German-Jewish boarding run by Anna Essinger, who had had the foresight to relocate from Germany in 1933. His fellow pupils included the artist Frank Auerbach, the musical humourist Gerard Hoffnung and playwright and critic Frank Marcus, author of The Killing of Sister George.

Brent’s life in England was funded by a refugee children’s charity, but when it ran out of money when he was 16, he became a chemistry lab assistant at Birmingham Central Technical College, studying part time. He received letters from his parents, forwarded by the Red Cross until autumn, 1942. He was later to discover that they had been shot in the woods in Riga, following a three day journey in packed cattle trucks.

Brent was too young to be interned, but his desire to serve his new country led him to volunteer for the Royal Warwickshire Regiment. He was sent for officer training and advised to change his name for fear of being captured and executed by the Germans, as a Jew. His adopted name Leslie came from the actor Leslie Howard, and he picked Brent from the phone book. It was several years before he added his true birth surname, Baruch.

He was demobbed in 1947 and opted to study zoology at Birmingham University. He was an outstanding sportsman and president of the students’ union, but although he just missed a First, his zoology professor Medaware encouraged him to undertake PhD research.

Brent’s published work includes A History of Transplantation Immunology (1997), Sunday’s Child? A Memoir (2009) and more than 200 papers. He retired in 1990 and was appointed Professor Emeritus at the University of London in 1990. Alongside his intellectual status and international honours, he remained a kind, mild-mannered and tolerant man, always in demand at conferences. He was involved in many worthy causes, including the AJR, of which he was a stalwart member, regularly attending their commemorative events. He was the driving force behind the AJR plaque dedicated to his former teacher Anna Essinger and gave an interview to the AJR Refugee Voices testimony collection, a summary of which is available from them. Leslie was aided by psychotherapy to help cope with the murder of his family. He commemorated them by inserting brass plaques (stolpersteine) into the pavement outside the family’s former Berlin home.

In November last year Brent spoke about his experiences as a Kind at Westminster Abbey to mark the 80th anniversary of Kristallnacht. His marriage to teacher Joanne Manley in 1954 ended in divorce and in 1991 he married psychotherapist Carol Martin, who survives him with the three children from his first marriage, Simon, Sue and Jenny, stepchildren Nicholas, David and Stan and nine grandchildren.

GLORIA TESSLER

Leslie Baruch Brent: born July 5, 1925. Died December 21, 2019