Immunohistochemical and ultrastructural identification of the pancreatic polypeptide-producing cell (PP-cell) in the human pancreas.

The consecutive semithin--thin section method was employed to identify pancreatic-polypeptide-containing cells in the human pancreas. The immunocytochemical staining of semithin sections with the peroxidase-antiperoxidase complex allowed a precise ultrastructural description of the immunoreactive cells on the adjacent thin section. Two populations of small granulated cells could be distinguished with this technique: one group is formed by cells whose secretory granules with a mean diameter of 141 nm show specific immunoperoxidase staining with anti-PP serum, while the other group consists of cells whose secretory granules measuring 118 nm in diameter show no immunoreactivity to anti-PP serum. The former cells which will be designated as PP-cells, are not identical with the D1-cells of the revised Wiesbaden classification of endocrine cells.