Nicholas Avrion Mitchison. 5 May 1928 — 28 December 2022

Abstract

Avrion Mitchison, universally known as Av, made enormous contributions to the field of cellular immunity. Working under Peter Medawar FRS during his PhD in Oxford, Av made the crucial discovery that viable lymphocytes were responsible for rejection of grafts of foreign tissue, initiating the field of cellular immunology, which was to preoccupy him throughout his career. In 1962 he was appointed head of the Division of Experimental Biology at the National Institute for Medical Research and began using proteins decorated with small synthetic molecules termed haptens, enabling him to make his second major discovery. He showed that optimal antibody responses to a hapten required the cooperation of two cell populations: bone-marrow-derived ‘B’ lymphocytes, which synthesized the antibody, and thymus-derived ‘T’ lymphocytes, which recognized moieties in the carrier protein molecule and provided help to the B cells. In 1971 Av became the Jodrell Professor of Zoology at University College London and head of the Imperial Cancer Research Fund Tumour Immunology Unit (TIU), where he continued to investigate how antibody and cytotoxic T cell responses are regulated and the role of major histocompatibility genes in this process. The TIU was a mecca for immunologists from around the world, and Av inspired those who passed through to make major contributions to cellular immunity, neuroimmunology, leukaemogenesis, tumour immunology and autoimmune disease. In 1991 he became the first director of the Rheumatism Research Centre in Berlin, and in a few short years after the fall of the Berlin wall established a flourishing institute. The annual award of the Mitchison Prize for Young Researchers honours his legacy.