S-100 protein immunoreactivity in human islets of Langerhans.

S-100 protein-containing cells were demonstrated by immunogold silver staining in human islets of Langerhans from patients with chronic pancreatitis (CP) with (n = 6) (Group I) or without (n = 6) (Group II) diabetes mellitus, (DM) and from nondiabetic, non-pancreatic controls (n = 6) (Group III). In all three groups S-100 protein containing cells were observed in all islets of Langerhans throughout the pancreas. Quantitative analysis of cell composition of islets did not reveal significant differences in S-100 protein cell content between the three groups. When double immunohistochemical staining was used to demonstrate different endocrine cell types (insulin, glucagon and pancreatic polypeptide) and S-100 protein immunoreactive cells, the latter proved to be a distinct cell type. Somatostatin-producing cells and S-100 protein-containing cells were usually also present as two distinct cell populations, but positive staining for both S-100 protein and somatostatin was occasionally observed within the same cells.