Non-invasive Tracking Of CD4~+T Cells With A Paramagnetic And Fluorescent Nanoparticle In Brain Ischemia

Recent studies have demonstrated that lymphocytes play a key role in ischemic brain injury. However, there is still a lack of viable approaches to non-invasively track infiltrating lymphocytes and reveal their key spatiotemporal events in the inflamed central nervous system(CNS). Here we describe an in vivo imaging approach for sequential monitoring of braininfiltrating CD4+ T cells in experimental ischemic stroke. We show that magnetic resonance imaging(MRI) or Xenogen imaging combined with labeling of SPIO-Molday ION Rhodamine-B(MIRB) can be used to monitor the dynamics of CD4+ T cells in a passive transfer model. MIRB-labeled CD4+ T cells can be longitudinally visualized in the mouse brain and peripheral organs such as the spleen and liver after cerebral ischemia. Immunostaining of tissue sections showed similar kinetics of MIRB-labeled CD4+ T cells when compared with in vivo observations. Our results demonstrated the use of MIRB coupled with in vivo imaging as a valid method to track CD4+ T cells in ischemic brain injury. This approach will facilitate future investigations to identify the dynamics and key spatiotemporal events for brain-infiltrating lymphocytes in CNS inflammatory diseases.