Humoral-mediated anti-islet cytotoxicity in diabetes-prone BB/OK rats--effect on beta-cell function and autologous islets.

The present study investigates whether sera from diabetic BB/OK rats impair beta-cell-specific functions of rat pancreatic islets and whether humoral-mediated cytotoxicity in BB rat sera also affects the autologous islets of normoglycaemic serum donors. Exposure of neonatal rat islets of Langerhans for 20 h to sera from diabetic BB rats and rabbit complement resulted in a decrease in insulin content and in insulin release upon glucose stimulation. However, the extent of islet alterations caused by sera from various BB rats was different as revealed by comparison of the ability of beta-cells to restore their functions during a 48 h recovery period. While the effect of some of the sera was completely reversible, in other cases the insulin content and/or the secretory capacity of the islets could not be fully restored indicating partially irreversible islet alterations due to pretreatment with cytotoxic BB rat serum. The potential effect of anti-islet cytotoxicity in BB rat sera against autologous islets of the serum donor indicated by enhanced 51Cr-release in the presence of rabbit complement was proven in 50% (6/12) of the investigated normoglycaemic BB/OK rats. These results suggest that humoral-mediated cytotoxicity may contribute to beta-cell alteration in this model of diabetes.