Abnormalities in dendritic cell and macrophage accumulation in the pancreas of nonobese diabetic (NOD) mice during the early neonatal period.

Dendritic cell (DC), macrophage (Mphi) and lymphocyte infiltrations have been observed in normal human perinatal pancreata, but have never been investigated so early in control mice. In type 1 diabetes-prone NOD mice, these cells are thought to infiltrate first the periphery of the islets of Langerhans around weaning before further islet infiltration and beta-cell destruction. We quantified, during the first month of life, the numbers of DC (characterized by CD11c positivity and dendritic morphology), histiocyte-like Mphi (characterized by ER-MP23 positivity) and Mphi with scavenging potential (characterized by BM8 positivity) in C57BL/6, DBA/2 and BALB/c control, and NOD and lymphocyte-deficient NODscid mouse pancreata. First, CD11c+ DC were present at low densities from birth onwards in control pancreata, while densities were higher in NOD and NODscid. Second, high numbers of BM8+ and ER-MP23+ Mphi were observed at birth in all strains investigated. After birth, particularly BM8+ cells disappeared progressively in control strains, but not in NOD and NODscid. Third, NOD mice also had more ER-MP23+ Mphi at birth compared to controls. Finally, DC and Mphi localizations were similar in all strains, i.e., mostly as dispersed cells in perivascular, periductular, peri-islet areas and interlobular septa. The most remarkable finding was that particularly BM8+ Mphi, were seen at sites of islet neogenesis and predominantly at the duct-islet interface. Our data showed that different types of APC were present in the pancreas during postnatal development in various control mouse strains and some differences were observed in NOD and NODscid mice from birth onwards.