Susumu Tonegawa is a molecular biologist who discovered and described the genetic mechanism through which the adaptive immune system generates millions of different antibodies.

By comparing the DNA of mature and embryonic B cells from mice, he noticed that the genes have been moved to different locations, recombined and also deleted to form the diversity of the antibodies regions.

He was awarded the Nobel Prize for Physiology or Medicine 1987 for this discovery. The diversity of production of anti-bodies by the adaptive immune system has been a central question in immunology for the past 100 years.

Before this big discovery, Tonegawa also uncovered the first cellular transcriptional enhancer element in association with the antibody gene complex.