Dendritic cells and scavenger macrophages in pancreatic islets of prediabetic BB rats.

Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease whose notorious pathologic feature is insulitis accompanied by destruction of beta-cells. In this morphological study, we examined the pancreatic events during the onset of diabetes in spontaneously diabetic BB/Organon rats. Dendritic cells were the first cells to accumulate around the islets, followed by lymphocytes. Scavenger macrophages and MHC class II-positive beta-cells were only seen late in the disease. These observations suggest a role for antigen-presenting dendritic cells in the onset of the beta-cell-specific autoimmune reaction and emphasize the necessity to distinguish between the several monocyte-macrophage subtypes in studies on the pathogenesis of IDDM.