Susumu Tonegawa
Tonegawa, Susumu (1939-) is a Japanese biologist who won the 1987 Nobel Prize in physiology or medicine for his research on the genetics of the immune system. He discovered how the body's immune cells, with a limited number of genes, can produce tailor-made antibodies to resist infection from millions of different viruses and bacteria.
Tonegawa was born in Nagoya, Japan, in 1939. He attended Hibiya High School in Tokyo. He graduated from the University of Kyoto in 1963 with a degree in chemistry, and that year began graduate studies in molecular biology at the University of California, San Diego. There, he researched genetic transcription in bacteriophages, and earned his Ph.D. degree in 1968. In 1971, he became a molecular biologist at the Institute of Immunology in Basel, Switzerland.
At the time Tonegawa arrived at the institute, immunologists were struggling with the problem of the origin of antibody diversity. When an organism is infected, it manufactures special proteins, called antibodies, to fight the invader. The “germ line” theory suggested that all the genes needed to make an antibody were part of the genetic code. The “somatic mutation” theory held that antibody genes mutate by rearranging themselves to code for different antibodies. Thus a small number of genes could generate large numbers of variants.
Tonegawa proved the somatic mutation theory by demonstrating that the parts of a DNA molecule mutate and recombine, or rearrange. This process can produce as many as 10 billion different kinds of antibodies. With Nobumichi Hozumi, Tonegawa discovered that the mutating DNA segments were separated by what appeared to be inactive, or noncoding, strands of DNA called introns. Tonegawa found that the introns contained a gene control element “enhancer.” His work in antibody genetics greatly aided research on the possible causes of cancer, particularly blood cancers such as leukemia and lymphoma.