George Davis Snell | Biography

One of three children, Snell was born on December 19, 1903, in Bradford, Massachusetts. By 1922, he had enrolled at Dartmouth pursuing studies in biology.

He obtained a B.S. degree in that subject in 1926 and enrolled at Harvard that same year to study genetics under the renowned biologist William Castle, who was among the first American scientists to delve into the biological laws of inheritance regarding mammals. Snell received a Ph.D. in 1930 after completing his dissertation on linkage (the means by which two or more genes on a chromosome are interrelated). That same year he became an instructor of zoology at Brown University, only to leave in 1931 to work at the University of Texas at Austin following receipt of a National Research Council Fellowship.

Snell's decision to accept the fellowship turned out to be a momentous one, as he began work for the famed geneticist Hermann Joseph Muller, whose research with fruit flies led to the discovery that x rays could produce mutations in genes. At the university, Snell experimented with mice, showing that x rays could produce mutations in rodents as well. Although Snell left the University of Texas in 1933 to serve as assistant professor at the University of Washington, he ventured to the Jackson Laboratory in Bar Harbor, Maine, in 1935 to return to research work. The laboratory, specializing in mammalian genetics, was well-known for its work in spite of its small size.

After continuing his work with x rays and mice, Snell decided to embark on a new study. Snell's project was concerned with the notion of transplants. Earlier scientific research had indicated that certain genes are responsible for whether a body would accept or reject a transplant. The precise genes responsible had not then been identified, however.

Snell began his experiments by performing transplants between mice with certain physical characteristics. He quickly discovered those mice with certain identical characteristics--in particular a twisted tail--tended to accept each other's skin grafts. In 1948 Peter Gorer came to Jackson Laboratory from London, England. Gorer, who had also conducted experiments on mice, developed an antiserum. He had discovered the existence of a certain antigen (foreign protein) in the blood of mice which induced an immune reaction when injected into other mice. Gorer had called this type of substance "Antigen II."

In collaboration, Snell and Gorer proved that Antigen II was present in mice with twisted tails, indicating that the genetics code for Gorer's antigen and the code found by Snell to be vital for tissue acceptance were identical. They called their discovery of this factor "H-2," for "Histocompatibility Two" (a term invented by Snell to describe whether a transplant would be accepted or rejected).

Later research revealed that instead of only a single gene being responsible for this factor, a number of closely related genes controlled histocompatibility. As a result, this was subsequently designated as the Major Histocompatibility Complex (MHC). The discovery of the MHC, and subsequent research by other scientists in the 1950s which proved it also existed in humans, made widespread organ transplantation possible. Donors and recipients could be matched (as had been done with blood types) to see if they were compatible.

Eventually Snell was able to produce what he called "congenic mice"--animals that are genetically identical except for one particular genetic characteristic. Unfortunately, the first strains of these mice were destroyed in a 1947 forest fire which burned down the laboratory. However, Snell's tenacity and dedication enabled him to rebound from this setback. Within three years he had created three strains of mice which differed genetically only in their ability to accept tissue grafts. The development of congenic strains of mice opened up a new field for experimental research, with Jackson Laboratory eventually being able to supply annually tens of thousands of these mice to other laboratories.

In 1952 Snell became staff scientific director and, in 1957, staff scientist at Jackson Laboratories. In those capacities he continued his research, particularly on the role that MHC plays in relation to cancer. Experiments he conducted with congenic mice found that on some occasions the mice rejected tumors which had been transplanted from their genetic twins. This "hybrid resistance" indicated that some tumors provoke an immune response, causing the body to produce antibodies to fight the tumor. This discovery could eventually be of great importance in developing weapons to fight cancer.

The success of Snell's work culminated in his winning the 1980 Nobel Prize in medicine or physiology for his work on histocompatibility. He shared this with two other immunogeneticists, Jean Dausset and Baruj Benacerraf. After being told of the Nobel committee's decision, Snell said there should have been a fourth recipient--his colleague Peter Gorer who died in 1962 and was thus ineligible to receive the prize.