B lymphocytes protect islet β cells in diabetes-prone NOD mice treated with imatinib

Imatinib (Gleevec) reverses type 1 diabetes (T1D) in NOD mice and is currently in clinical trials in individuals with recent-onset disease, While research has demonstrated that imatinib protects islet beta cells from the harmful effects of ER stress, the role the immune system plays in its reversal of T1D has been less well understood, and specific cellular immune targets have not been identified. In this study, we demonstrate that B lymphocytes, an immune subset that normally drives diabetes pathology, are unexpectedly required for reversal of hyperglycemia in NOD mice treated with imatinib. In the presence of B lymphocytes, reversal was linked to an increase in serum insulin concentration, but not an increase in islet beta cell mass or proliferation. However, improved beta cell function was reflected by a partial recovery of expression of the transcription factor MafA, a sensitive marker of islet beta cell stress that is important for adult beta cell function. Imatinib treatment was found to increase the antioxidant capacity of B lymphocytes. improving ROS handling in NOD islets. This study reveals a mechanism through which imatinib enables B lymphocytes to orchestrate functional recovery of T1D beta cells.