Zelig Eshhar, an immunologist whose breakthrough research in the 1980s created a critical pathway to developing immunotherapies that attack particular cancers, died on July 3 at Tel Yitzhak, a kibbutz in central Israel. He was 84.

Dr. Eshhar’s exploration of the human immune system began in the 1960s, during his Ph.D. studies at the Weizmann Institute of Science in Rehovot, near Tel Aviv. There, he focused on the T-cell, a type of white blood cell with the natural ability to fight germs and disease. Dr. Eshhar’s CAR-T leap is the fundamental science behind immunotherapies that since 2017 have been approved by the F.D.A. to treat blood cancers like acute lymphoblastic leukemia, non-Hodgkin lymphoma and multiple myeloma. Small clinical trials of CAR-T therapies for ovarian and colorectal cancers have also shown promise, according to the National Cancer Institute.