In addition to the lymph nodes close to the vaccination site (mean uptake of 20.8% ID/cc), immunoPET imaging with 89Zr-DFO-OX40 mAb showed a significant and specific OX40-positive signal in the spleen (16.7% ID/cc) and tumor-draining lymph nodes (11.4% ID/cc). Here, TNFRSF4 is linked to neoplasm.