The aim of the investigation was to study the distribution of S100-positive cells in the islets of Langerhans of human pancreas during prenatal and early postnatal development, as well as in adult humans.Materials and Methods. using antibodies to S100 protein, to main hormones produced in the islets of Langerhans in human pancreas (insulin, glucagon and somatostatin), and to neuron-specific enolase (NSE) we carried out an immunohistochemical analysis of human pancreatic samples. The samples were taken from adults without pancreatic diseases, from patients with type 2 diabetes mellitus, as well as from fetuses and newborns.Results. Two types of S100-positive cells can be found in human islets of Langerhans starting from gestation week 15-16: cells located on islet periphery, and cells situated inside an islet. Cells located on periphery are flattened and have small amount of cytoplasm. These cells have long processes extending mainly along periphery. The cells located inside islets are oval-or round-shaped, and generally have no processes.Conclusion. In an early fetal period in islets of Langerhans of human pancreas, two types of S100-positive cells appear, they being different in their structure. The cells on periphery are similar morphologically to glial cells. The cells inside islets are no different in their structure from other endocrine cells. Two types of S100-positive cells can be suggested to be of importance both in islet morphology, and in the regulation of hormones expressed by endocrine cells.

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