Development of autoimmune diabetes in both humans and mice is preceded by a prolonged period of inflammation of pancreatic islets by autoreactive T-cells. Noninvasive imaging techniques, including positronemission tomography and optical or magnetic resonance imaging, have been used to track the recruitment of lymphocytes to sites of inflammation. These techniques, however, rely on labeling strategies that are non-antigen specific and do not allow specific tracking of the recruitment of autoreactive lymphocytes. Here we describe an antigen-specific magnetic label to selectively target a prevalent population of diabetogenic CD8