Frank Macfarlane Burnet

Proposed by Burnet in 1957, the clonal selection theory states that each lymphocyte carries receptors for one specific antigen, and when that antigen binds, the lymphocyte is stimulated to proliferate into a clone of identical cells that produce antibodies or mount a cellular response. This replaced earlier instructional theories that held antibodies were shaped by the antigen after exposure.

Burnet shared the 1960 Nobel Prize in Physiology or Medicine with Peter Medawar for the discovery of acquired immunological tolerance—the principle that the immune system can be rendered unresponsive to antigens encountered during early development. This work provided the theoretical foundation for later advances in organ transplantation.

Burnet spent the majority of his career at the Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia, serving as its director from 1944 to 1965. Under his leadership, the institute became one of the world's leading centers for immunology and virology research.

Before his immunological breakthroughs, Burnet made significant contributions to virology, including pioneering work on influenza virus replication and the discovery that the influenza virus undergoes recombination (reassortment) in host cells. He also developed techniques for cultivating viruses in chicken embryos that became standard laboratory methods for decades.