This approach was employed during anti-CTLA-4 treatment in colon cancer xenograft models using a murine 89Zr-labelled anti-CD3 antibody ([89Zr]Zr-DFO-CD3) to quantify T-cell infiltration; interestingly high levels of infiltrations were found to precede tumour regression 86. Here, CTLA4 is linked to neoplasm.