PANCREATIC DUCT INFILTRATION IN THE LOW-DOSE STREPTOZOCIN-TREATED MOUSE

The pancreatic-duct system was observed during the initial stage of ty pe 1 diabetes in C57BL/6J mice rendered diabetic with low doses of str eptozocin. Light microscopy revealed that the ducts located in close p roximity to islets (islet ducts) were involved in the infiltrating pro cess: inflammatory cells extended from the islets to these ducts. Howe ver, ducts that were located far from islets (non-islet ducts) were ge nerally free from infiltration. Immunocytochemistry revealed that both islet ducts and non-islet ducts express MHC class II and ICAM-1 molec ules: this positivity seems to be mainly expressed by elements infiltr ating the connective layer or by endothelia of vessels surrounding duc ts. Strong ICAM-1 positivity demonstrates that adhesiveness is widely represented in early diabetes in this animal model. At the ultrastruct ural level only a few endocrine elements were observed scattered withi n the epithelial layer and single infiltrating elements were rarely en countered 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 w ith the hypothesis of an initially more widespread and less specific p rocess that later undergoes restriction.