Pancreatic duct infiltration in the low-dose streptozocin-treated mouse

The pancreatic-duct system was observed during the initial stage of type 1 diabetes in C57BL/6J mice rendered diabetic with low doses of streptozocin. Light microscopy revealed that the ducts located in close proximity to islets (islet ducts) were involved in the infiltrating process: inflammatory cells extended from the islets to these ducts. However, ducts that were located far from islets (non-islet ducts) were generally free from infiltration. Immunocytochemistry revealed that both islet ducts and non-islet ducts express MHC class II and ICAM-1 molecules: this positivity seems to be mainly expressed by elements infiltrating the connective layer or by endothelial of vessels surrounding ducts. Strong ICAM-1 positivity demonstrates that adhesiveness is widely represented in early diabetes in this animal model. At the ultrastructural level only a few endocrine elements were observed scattered within the epithelial layer and single infiltrating elements were rarely encountered within the connective layer of ducts. The existence of other sites of "activation" other than the islets of Langerhans, in this as well as in other animal models of types 1 diabetes, is consistent with the hypothesis of an initially more widespread and less specific process that later undergoes restriction.