The areas of investigation upon which he left his mark include the immunoglobulins and the complement system.
[1] He spent three years with Henry G. Kunkel at the Rockefeller University, where he became interested in immunological research, and investigated γ-globulin.
[1][4] Later he worked at Uppsala University with Gunnar Wallanius on the complement system,[5] and obtained his doctorate there.
[1] After six years in the Kunkel laboratory, he was recruited by Frank Dixon to join the Scripps Clinic and Research Foundation in La Jolla, where he was appointed to the Cecil H. and Ida M. Green Chair in Medical Research in 1972.
After problems at Scripps he returned to Germany, at the Bernhard Nocht Institute for Tropical Medicine.