A graduate of Northwestern University, Dr. Ritz received his MD from Chicago Medical School in 1972, followed by a residency in internal medicine at the University of Wisconsin Hospital, Madison. Dr. Ritz completed a clinical fellowship in Hematology and Oncology at Beth Israel Hospital and a research fellowship at the Dana-Farber Cancer Institute, where he joined the staff in 1980. Dr. Ritz was a Scholar of the Leukemia Society of America and is a recipient of the prestigious Stohlman Scholar Award. He is an expert in bone marrow transplantation and cancer immunology. He generated some of the first monoclonal antibodies reactive with human leukemia cells and developed methods for processing human bone marrow to specifically deplete target cell populations. These methods have been used to deplete residual tumor cells from autologous bone marrow and donor T cells that cause graft versus host disease from normal allogeneic marrow prior to stem cell transplantation.

Dr. Ritz is Director of the Connell-O'Reilly Cell Manipulation Core Facility (CMCF) and a Professor of Medicine at Harvard Medical School. The CMCF provides hematopoietic stem cells for patients who are undergoing hematopoietic stem cell transplantation and manufactured cellular products of various types for patients enrolled on clinical trials evaluating novel cellular therapies for cancer. Dr. Ritz is a member of the Executive Committee of the Dana-Farber/Harvard Cancer Center and the Associate Director for Core Facilities at DF/HCC. He is also a Co-Director of the Center for Human Cell Therapy at the CBR Institute for Biomedical Research and a member of the Executive Committee of the Harvard Stem Cell Institute. Dr. Ritz's current laboratory research focuses on immune reconstitution after hematopoietic stem cell transplantation, cellular therapies and immunotherapy of cancer.