His research into the structure of genes which carry the code for antibody molecules was of major significance.
The main focus of this inquiry was the question of how the vast diversity of antibody molecules is formed by a limited number of encoded genes.
Leder's work on antibody genes was later extended to research into Burkitt's lymphoma, a tumour of antibody-producing cells, which involves the oncogene c-myc.
In 1968, Leder headed the Biochemistry Department of the Graduate Program of the Foundation for Advanced Education in the Sciences at the National Institute of Health.
In November 2015 he has been awarded an honorary doctoral degree from the Medical Faculty of the University of Basel for his lifetime achievements.