Immunohistochemical localization of human pancreatic polypeptide (HPP) to a population of islet cells

HPP is the human counterpart of APP--a polypeptide that has been isolated from avian pancreas and shown to exert pronounced biological effects. The availability of anti-HPP serum enabled us to use immunohistochemical procedures for the localization of HPP in human pancreas. A small population of pancreatic islet cells showed strong immunofluorescence after staining with anti-HPP serum. The HPP cells were mainly localized at the periphery of the islets. Sometimes they were also seen scattered in the exocrine parenchyma as well as within the epithelium of small to medium-sized ducts. While rare in the pancreas of adult man, HPP cells were abundant in certain parts of the pancreas of foetuses (18-20 weeks gestational age). Their staining properties showed them to be distinct from the A, Band D cells of the pancreatic islets.