Accumulation ofIodine Labeled Interleukin-2 in the Pancreas of NOD Mice

Interleukin-2 (IL-2) is an important cytokine in the autoimmune process proceeding Type 1 diabetes. Our aim was to investigate, in two previously used animal models, the NOD mouse and the BB/W rat, the in vivo tissue distribution of radio-labeled IL-2. If the radio-labeled IL-2 accumulated significantly in the pancreas compared to surrounding organs it could allow imaging of lymphocyte infiltration of the islets of Langerhans by scintigraphic methods. IL-2 was labeled enzymatically with¹²⁵Iodine. Radio-labeled IL-2 was injected iv in prediabetic NOD mice, diabetic NOD mice and Balb/c mice in the first animal model and in BB rats in the second model. Animals were sacrificed at different time points and the activity in different organs was measured. It was found that the mean activity in the pancreas in both diabetic and prediabetic NOD mice was significantly higher compared to pancreas from Balb/c mice (P< 0.001 and P=0.005, respectively). However, the mean activity in the pancreas was at the lower range of the surrounding organs in both animal models, thereby excluding the possibility of imaging the autoimmune process by scintigraphic methods. It is concluded that radio-labeled IL-2 did accumulate significantly in the pancreas of NOD mice compared to control mice but there is a need to develop new techniques in order to visualize the localized activity.