Ralph M. Steinman was born in Montreal, Canada, on 14 January 1943, the second of four children. His father Irving, a Jewish immigrant from Eastern Europe, and his mother Nettie owned a department store in Sherbrooke near Montreal. His father wanted him to continue in the family business, but in high school Ralph became interested in science. He received a B.S. with honors from McGill University in 1963, and an M.D. magna cum laude from Harvard Medical School in 1968. While at Harvard, he spent a year as a research fellow in the laboratory of Elizabeth Hay, who introduced him to cell biology and the immune system. During his internship and residency at the Massachusetts General Hospital, Steinman met Claudia Hoeffel, who was a medical social worker in the hospital. They married in 1971.

After completing his medical training, he was drawn to biomedical research. He joined The Rockefeller University in 1970 as a postdoctoral fellow in the Laboratory of Cellular Physiology and Immunology headed by physician-scientists Zanvil A. Cohn and James G. Hirsch. This laboratory was founded by the premier microbiologist René Dubos, who recognized the need to study the host during infection. Dubos, Cohn, and Hirsch were Steinman’s ideal mentors whose approach was not limited to immunology but embraced cell biology and biochemistry. He spent his entire career at Rockefeller, where he was appointed assistant professor in 1972, associate professor in 1976, and professor in 1988. He was named Henry G. Kunkel Professor in 1995 and director of the Christopher Browne Center for Immunology and Immune Diseases in 1998.

Steinman’s early research in collaboration with Cohn was an attempt to understand the white cells of the immune system that operate in a variety of ways to spot, apprehend, and destroy infectious microorganisms and tumor cells. In 1973, Steinman and Cohn discovered dendritic cells, a previously unknown class of immune cells that constantly formed and retracted their processes. This discovery changed the field of immunology.

For the next four decades, until his death in 2011, Steinman’s laboratory was at the forefront of dendritic cell research. He and his colleagues established that dendritic cells are critical sentinels of the immune system that control both its innate and adaptive responses – from silencing to actively resisting its challenges. He also showed that dendritic cells are the 2 main initiators of T cell-mediated immune responses. Steinman’s deep insights into medicine led him to take his dendritic cell research into the treatment of human disease. His most recent studies were focused on the interface of several diseases with the immune system and included clinical studies using dendritic cell- and immune-based vaccines and therapies for such medical conditions as graft rejection, resistance to tumors, autoimmune diseases, and infections. In 2010, he initiated at The Rockefeller University Hospital a phase I clinical trial with the first dendritic cell-targeted vaccine against HIV.

Steinman’s dynamic personality, boundless energy, and persistent leadership during these four decades allowed him to build international collaborations with many immunologists and scientists in other fields and to create an entire new field of dendritic cell biology. As part of his efforts in establishing this science, he personally trained and mentored more than a hundred postdoctoral fellows and graduate students in his laboratory. He published some 450 scientific papers. Beginning in 1978, he became editor of the Journal of Experimental Medicine and was one of its guiding forces. He also served as advisory editor of Human Immunology, the Journal of Clinical Immunology, the Journal of Immunologic Methods and the Proceedings of the National Academy of Sciences.

For the first two decades of Steinman’s research, dendritic cells were underappreciated, but by the mid-1990s, the scientific community began to recognize his work on their critical role in the immune system. Steinman received numerous honors, including the Freidrich-Sasse (1996), Emil von Behring (1996), and Robert Koch (1999) Prizes, the Rudolf Virchow (1997) and Coley (1998) Medals. In 2004, he received the New York City Mayor’s Award for Science and Technology. He was honored with the Gairdner Foundation International Award in 2003, the Albert Lasker Award for Basic Medical Research in 2007, the Albany Medical Prize in 2009, and the A.H. Heineken Prize for Medicine in 2010. He was awarded honorary degrees from the University of Innsbruck, Free University of Brussels, Erlangen University, and the Mount Sinai School of Medicine. He was elected a member of the National Academy of Sciences in 2001 and the Institute of Medicine in 2002. He was also a corresponding fellow of the Royal Society of Edinburgh. In 2012, the Ralph M. Steinman Center for Cancer Vaccines was established in his honor at the Baylor Institute for Immunology Research in Dallas, Texas.

Steinman was a trustee of the Trudeau Institute in Saranac Lake, New York. He also served as a scientific advisor to several organizations including the Charles A. Dana Foundation, the Campbell Family Institute of Breast Cancer Research in Toronto, Canada, the M. D. Anderson Cancer Center for Immunology Research in Houston, Texas, Baylor Institute for Immunology Research, RIKEN Center for Allergy and Immunology Research in Yokohama, Japan, and CHAVI Center for HIV-AIDS Vaccine Immunology, Durham, North Carolina. Steinman was a member of the American Society of Clinical Investigation, the American Society of Cell Biology, the American Association of Immunologists, the Harvey, the Kunkel, and the Practitioners’ Societies, and the Society for Leukocyte Biology.

Diagnosed with pancreatic adenocarcinoma in March 2007, Steinman believed that dendritic cells had the potential to fight his aggressive tumor. With many collaborators and leading-edge technology, he designed dendritic cell-based immunotherapies for himself that he thought might also advance medical science. For four-and-a-half years after his diagnosis, he remained quite healthy and continued to travel, lecture, and pursue new laboratory studies. Steinman died on 30 September 2011, three days before his Nobel Prize was announced. Unaware of his death at the time of its announcement, the Nobel Committee made an unprecedented decision that his award would stand. In addition to his wife Claudia, Steinman was survived by his three children Adam, Alexis, and Lesley, three grandchildren Isadola, Syla, and Robert; his mother Nettie; his brothers Seymour and Mark; his sister Joni; his daughter-in-law Jenny and his son-in-law Joseph.

Claudia Steinman and her children have donated the entire proceeds of Dr. Steinman’s Nobel Prize to charity, $500,000 of which they are giving to the Cohn-Steinman Professorship at the Rockefeller University and $250,000 to The Steinman Family Foundation to support the careers of young scientists and science education.