Date of issue: September 10, 2020
Series: Medical Groundbreakers
Design: Mike Savage, Dale Kilian
James Till and Ernest McCulloch
James Till was born in 1931 in Lloydminster, Alberta. After receiving his Ph.D. in biophysics at Yale University, he returned to Canada to work at the Ontario Cancer Institute at Princess Margaret Hospital, Toronto. Ernest McCulloch was born in 1926 in Toronto and received his medical training at the University of Toronto. Following research work at the Lister Institute in London, England, he also joined the Ontario Cancer Institute, where he met Till.
The two researchers combined their knowledge of biophysics and haematology to investigate the development of normal and abnormal blood cells, eventually showing that progenitor (stem) cells were capable of differentiating into all blood cell types. In collaboration with molecular biologist Lou Siminovitch, they went on to show that these cells were capable of self-renewal. This work laid the foundation for the development of regenerative medicine and introduced new treatment options for previously lethal malignancies, such as acute leukemia, via stem cell transplantation.
McCulloch is seen on the left writing on a blackboard; Till is on the right. A longitudinal section of a mouse femur with prominent red bone marrow which they used for their investigations is seen at the bottom left. Above this (and on the first-day cover), two cells can be seen in the process of replication. Both Till and McCulloch were awarded the Order of Canada (the medal located in the stamp's top left corner).