His father Irving (born Isador) was born in Bessarabia. Steinman's early re- search 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 cri- tical sentinels of the immune system that control both its innate and adaptive respon- ses - 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 rejec- tion, resistance to tumors, autoimmune diseases, and infections. In 2010, he initiated at The Rockefeller University Hos