Capturing the dynamic information rising from the interactions between cancer cells and T cells requires the selection of suitable biomarkers,130 with radiolabeled PET probes being in a more advanced translational state, as recently reviewed by Whitney and Aarntzen.131 The molecular targets for T cells are relatively diverse, from generic surface receptors (e.g., CD4, CD8) to T cell activation markers (e.g., PD-1, LAG-3, OX40, IL-2) or more recently, metabolic markers (e.g., 18F-labeled amino acids and nucleobases). The gene discussed is IL2; the disease is cancer.