He was educated at Leighton Park School and secured a Classics scholarship to Balliol College.
[3] Mitchison's contributions to immunology include the discovery of both low dose and high dose tolerance for a single antigen,[4] a surprising result in the context of basic clonal selection theory, but which can be understood in the context of immune network theory.
He was also a founder member of the British Society for Immunology alongside John H. Humphrey, Bob White, and Robin Coombs.
He held an Honorary Doctorate from the Weizmann Institute and in 1995 was awarded the Novartis Prize for Basic Immunology.
In honor of its Founding Director, the Deutsches Rheuma-Forschungszentrum Berlin (DRFZ), a Leibniz Institute, annually awards the Avrion Mitchison Prize to young scientists contributing significantly to understanding and treating rheumatic diseases.