Herman Eisen’s first faculty position was at NYU in the then-new Department of Industrial Medicine, where he was funded to work part-time as a researcher and invest the remainder of his time in clinical practice. He found this combination unsustainable and therefore was receptive when approached by Barry Wood to recruit him to Washington University School of Medicine as the Chief of Dermatology there. Eisen moved to Washington University in 1955 and spent five years in the position before moving to the Department of Microbiology and serving as its chair. Following the National Cancer Act of 1971, Salvador Luria recruited Eisen to become one of the founding members of MIT’s new Center for Cancer Research, where Eisen would spend the rest of his career. Eisen officially retired in 1989, assuming professor emeritus status, but remained active in research and in mentoring younger scientists in the MIT community. During this time he worked with a number of MIT colleagues on their ongoing projects, including Jianzhu Chen and Arup Chakraborty. Herman Eisen was elected a fellow of the American Academy of Arts and Sciences in 1965, a member of the National Academy of Sciences in 1969, and a member of the Institute of Medicine in 1974. He served as the president of the American Association of Immunologists in 1968–69 and received the organization’s Lifetime Achievement Award in 1997.

Herman Eisen’s research is regarded as foundational in the field of immunology. After his death, he was remembered as “the last of the great immunochemists”. He is particularly well known for his studies of affinity maturation of antibodies beginning in the late 1950s while he was at Washington University. Much of this work was conducted with postdoctoral fellow Lisa Steiner, who went on to become the first woman in the MIT Department of Biology. In the 1980s Eisen changed research interests from a focus on antibodies to a focus on T cells and cell-mediated immunity. Herman Eisen’s wife Natalie was also a physician and practiced as a pediatrician in New York, served as Assistant Director of Bellevue Hospital in St. Louis, and then practiced at the Harvard Street Neighborhood Health Center in Boston. The couple had five children. Eisen remained an active research scientist for many years following his official retirement and was working on a manuscript related to antibody affinity the day he died in 2014.