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08/05/2026 | Press release | Distributed by Public on 08/05/2026 12:19

Nobel Laureate and UC San Diego Alumnus Susumu Tonegawa (1939-2026)

Published Date

August 05, 2026

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Molecular biologist Susumu Tonegawa, who made fundamental contributions to immunology and neurobiology and became UC San Diego's first alumnus to receive a Nobel Prize, passed away on July 11. He was 86.

Tonegawa led a remarkable career that spanned two areas of biology across several decades. His Nobel Prize-winning research, honored in 1987, resolved a long-standing puzzle about how the immune system generates millions of antibodies from a small set of genes. His pioneering work demonstrated that developing immune cells physically rearrange segments of their DNA to generate distinct antibody genes, enabling the immune system to recognize an extraordinary range of foreign molecules and biological threats. This discovery fundamentally changed scientists' understanding of both immunity and genome organization.

Molecular biologist Susumu Tonegawa. Credit: Webb Chappell, courtesy of MIT

The Nobel Prize committee praised the discoveries and their "possibilities to increase the immune response against pathogenic microorganism through vaccination - and also to improve inhibition of unwanted immune reactions."

Tonegawa shifted his interests in later years to neuroscience, during which he studied learning processes and how memories are stored, recalled, reassigned and deleted.

"Susumu Tonegawa's life and work reflect the transformative impact of discovery at its highest level. As UC San Diego's first alumnus to receive a Nobel Prize, he helped establish a legacy of scientific excellence that continues to inspire our campus and the broader research community, " said Chancellor Pradeep K. Khosla. "His groundbreaking contributions to immunology and neuroscience advanced our understanding of some of biology's most fundamental processes and remain a source of pride for UC San Diego."

The first Japanese scientist to win the Nobel Prize in Physiology or Medicine, Tonegawa was later joined by fellow UC San Diego School of Biological Sciences alumni Nobel laureates Bruce Beutler (2011), former graduate student Venkatraman Ramakrishnan (2009) and, most recently, Fred Ramsdell (2025).

"Susumu Tonegawa embodied the curiosity, originality and intellectual ambition that define great science," said School of Biological Sciences Dean Kit Pogliano. "From his doctoral studies of bacteriophage gene regulation at UC San Diego, to his Nobel Prize-winning discovery of antibody-gene rearrangement, to his pioneering identification of the neural ensembles that encode memories, he repeatedly revealed hidden mechanisms underlying life's remarkable complexity. We are proud that UC San Diego and the larger UC San Diego scientific community were part of his scientific journey, and deeply grateful for the example he leaves to generations of scientists."

Born in Nagoya, Japan, in 1939, Tonegawa studied at Kyoto University, and after graduation joined the university's Institute for Virus Research. He was accepted to UC San Diego Biology's new graduate program in molecular biology, where he studied bacteriophage gene transcription in the lab of Professor Masaki Hayashi. He earned his PhD in 1968, after which he took a postdoctoral position with Professor Renato Dulbecco at the Salk Institute. After working at the Basel Institute for Immunology, Tonegawa was recruited to MIT in 1981, where he served as a faculty member for more than 40 years.

"Few scientists have reshaped our understanding of biology as profoundly as Susumu Tonegawa," said Myriam Heiman, director of MIT's Picower Institute, where Tonegawa served as founding director, in a release issued by MIT. "His intellectual fearlessness, extraordinary creativity and relentless pursuit of fundamental questions opened entirely new frontiers in both immunology and neuroscience. His influence on science and on the people who had the privilege of working alongside him is immeasurable."

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