Snell made fundamental contributions to transplantation genetics. At his suggestion genes governing transplantation were called histocompatibility genes and Gorer’s Antigen II became Histocompatibility-2 (H-2).

In 1980 Snell shared the Nobel Prize in Physiology or Medicine with B. Benacerraf and J. Dausset "for their discoveries concerning genetically determined structures on the cell surface that regulate immunological reactions."

Antigen II, discovered by Gorer (No. 2576.5), was studied by Snell and became known as the product of the H-2 locus, the fundamental locus in the history of mammalian transplant biology.