By visualizing DTA-1 with the FITC-conjugated anti-rat IgG2b mAb, it was demonstrated that the tumor-infiltrating CD4+ Foxp3+ Treg population bound predominantly with DTA-1 at 6 hrs after i.t. injection (Fig. 4C), in parallel with the disappearance of tumoral Treg cells after treatment with DTA-1. Here, CD4 is linked to neoplasm.