Katz then became senior investigator in the dermatology branch of the
National Cancer Institute (1974–2014) and assumed the position of acting chief in 1977. In 1980, he became chief of the branch, a position he held until 2002. In 1989, Katz also assumed the position of Marion B. Sulzberger Professor of Dermatology at the
Uniformed Services University of the Health Sciences, a position that he held until 1995. Katz focused his studies on immunology and the skin. His research demonstrated that skin is an important component of the
immune system both in its normal function and as a target in immunologically-mediated disease. In addition to studying
Langerhans cells and epidermally-derived
cytokines, Katz and his colleagues investigated inherited and acquired blistering skin diseases. Katz trained a large number of immunodermatologists in the U.S., Japan, Korea, and Europe. Katz was a former president of the Society for Investigative Dermatology,
The International League of Dermatological Societies, and the International Committee of Dermatology. In 1995, the NIH director,
Harold E. Varmus selected Katz as the second director of
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). He served as director from August 1994 until he died on December 20, 2018. == Awards and honors ==