From 1953 to 1962, he headed the immunoserology division at the department of
serology at the Japanese National Institute of Health. During his tenure in that position he spent two years as a research fellow at
Caltech (1957–1959). In 1962, Ishizaka and his wife
Teruko were recruited by Sam Bukantz, medical director of the Children's Asthma Research Institute and Hospital (CARIH), and moved to Denver, Colorado. He assumed the post of assistant professor of
microbiology at the
University of Colorado Medical School, as well as chief of immunology of its associated Children's Asthma Research Institute In 1965, he was promoted to associate professor at University of Colorado Denver. and its interplay with
mast cells. They demonstrated the IgE's critical role in mediating the release of
histamine from mast cells. The discovery of IgE is considered a milestone in immunology and the understanding of allergy. Ishaka remained at the university until 1989, After retiring in 1996, he returned to Japan and served as honorary director of the Institute of Immunology at
Yamagata University. == Recognition ==