Nobashi and colleagues evaluated a 89Zr-labeled DFO-chelated OX40 monoclonal antibody PET tracer to track activated T-cells in a murine orthotopic glioma model.56 Immune-PET detected high OX40 levels in lymphoid organs (ie, axillary and cervical lymph nodes, spleen) and correlated with tumor regression. The gene discussed is TNFRSF4; the disease is central nervous system cancer.