Eva Klein, MD, PhD, FAACR: In Memoriam (1925–2025)

Dr. Eva Klein, a trailblazing scientist whose groundbreaking research shaped the field of cancer immunology, has passed away 3 days short of her 100th birthday.Klein was born in Budapest, Hungary, in 1925. As a young medical student, she moved with her husband Georg Klein to Stockholm where they started their research careers in the laboratory of Professor Torbjörn Casperssen who had a major influence on Klein’s career, inspiring her to create her own distinct research profile. Klein received her MD degree in 1953 and defended her PhD thesis in 1955. In 1958, Georg Klein and Eva Klein became heads of the new Department of Tumor Biology at Karolinska Institutet, where they created a very international and cross-disciplinary team working on genetics and cytogenetics, tumor virology, immunology, mouse models, and, during the later years, molecular biology.Klein was named full professor in tumor biology at Karolinska in 1969. She was subsequently elected to the Nobel Assembly at Karolinska in 1986 and to the Royal Swedish Academy of Sciences in 1987, and she was inducted as a fellow of the American Association for Cancer Research Academy in 2013. She also received several additional accolades over the years for her achievements:2011 200-year Anniversary Silver Medal for Medical Research, Karolinska Institutet2003 Mendel Honorary Medal for Merit in Biological Sciences2002 Fellow, European Union Against Cancer1993 Member of the Hungarian Academy of Sciences1975 Award in Tumor Immunology, Cancer Research Institute of New YorkKlein’s passion for science led her to a distinguished career in which her research gained international recognition. Among her many achievements, she was instrumental in the discovery and characterization of NK cells, lymphocytes that play a crucial role in the body’s defense against cancer. Her investigations into the Epstein–Barr virus and its connection to Burkitt lymphoma further expanded the scientific understanding of virus-induced cancers. Klein also worked with her husband to study the DNA content of carcinoma ascites cells, and this research showed a correlation between cancer growth and the cellular DNA content and demonstrated that tumor cells have chromosomal abnormalities.Over the course of her prolific career, Klein published more than 500 scientific articles, many of which became landmark contributions to cancer immunology. Her work helped establish cancer immunology as a vital research field, laying the basis for cancer treatments that have saved the lives of many patients and new immunotherapies still being developed today.For those of us fortunate enough to have known her, she was far more than a professor or scientist. She was a beacon of creativity, a champion of individuality, and most importantly a deeply warm and generous soul.Klein was a scientist who did not just think outside the box—she seemed to dismantle the box entirely. Her ideas were bold, her questions were unconventional, and she had the courage to venture down paths that others were too cautious to tread. Whereas others may have followed trends, she carved her own trail, unafraid to challenge norms and push boundaries. Her work did not just advance her research field, but it inspired those around her to think wider, dream bigger, and believe in the power of curiosity.But as brilliant as she was in her science, it was her humanity that left the most profound mark and impression on us. Klein had a gift for seeing the essence of every person she met. She had an uncanny ability to look past titles, roles, or facades and to truly understand the heart of a person. Her interest in people was genuine and infectious. She listened not just with her ears but with her whole being, making everyone feel valued, understood, and seen.She was generous with her time, her wisdom, and her kindness. She did not just mentor, but she nurtured. She did not just teach, but she inspired. Whether you were her colleague, her student, or a stranger passing through her life, Klein made you feel like you mattered. She made us all better, not just as thinkers or scientists but as human beings.Klein’s contributions to science will endure as a cornerstone of modern cancer research. She leaves behind an indelible impact on medicine and a profound example of scientific curiosity, perseverance, and excellence. Her legacy will assuredly continue through the generations of scientists she trained and inspired.