Preface: Franz-Josef Kaup and the development of the Pathology Unit at the German Primate Center.

This special issue about selected diseases of nonhuman primates was created in honor of Franz-Josef Kaup, who worked as a primate pathologist at the German Primate Center (DPZ) for 25 years. In 1992, Franz-Josef Kaup started his career at the DPZ as head of the working group Experimental Pathology. Prior to that he worked as a research assistant in the division Electron Microscopy at the Institute of Pathology of the University of Veterinary Medicine in Hanover. He was very experienced in the field of electron microscopy and used this expertise to establish a central electron microscopy laboratory at the DPZ. In the beginning, research of the working group Experimental Pathology was focused on gastrointestinal and respiratory infections and was closely related to projects of the Department of Virology. At that time, experimental infections of rhesus macaques with simian immunodeficiency virus (SIV) and associated opportunistic infections became the main subject of his research. The contribution of Christiane Stahl-Hennig and coauthors about SIV-induced cardiovascular diseases reflects the still ongoing collaboration in this research field. After merging the Experimental Pathology and Primate Husbandry in 1996, Franz-Josef Kaup headed the newly created Department of Veterinary Medicine and Primate Husbandry. This department became the central service unit of the DPZ in 1999 and offered a broad spectrum of services in veterinary diagnostics, primate husbandry, and animal welfare, which was intensively used by many internal and external scientists. In 2001, Walter Bodemer joined the group and the scientific contents expanded with a new focus on the pathogenesis of prion diseases. Some important aspects of this era are summarized in the work of Walter Bodemer.