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Landsteiner, renowned as an immunologist, made significant contributions to the field of immunology. His groundbreaking work on blood groups and the discovery of the ABO blood group system revolutionized blood transfusion practices, ensuring safer transfusions and saving countless lives. Additionally, his pioneering research laid the foundation for organ transplantation and the study of autoimmune diseases. Landsteiner's expertise and dedication to immunology left a lasting impact on medical science.