When merely looking at the PET tumor uptake of 89Zr-DFO-CD4 and 89Zr-DFO-CD8a across syngeneic mouse models, imaging of CD4+ and CD8a+ cells did not completely match the assessment of immune status by IHC and flow cytometry in this study with discrepancies mainly found among the immunogenic CT26 and MC38 models (low uptake) and poorly immunogenic P815 (high uptake) model. This evidence concerns the gene CD4 and neoplasm.