Several mouse studies and early clinical trials have already indicated the value of noninvasive imaging of CD4+ cells in rheumatoid arthritis (20), colitis (21), allogeneic stem cell transplantation (44), organ transplant rejection (45), acquired immunodeficiency disease (10), and in the context of cancer immunotherapies (46), using radiolabeled full-length antibodies or fragments thereof. This evidence concerns the gene CD4 and cancer.