Fluorescent immunohistological studies using double labeling with anti-rat IgG2b mAb (for DTA-1) and F4/80- (for macrophages) or Foxp3- (for Tregs) specific mAbs were performed to determine the mechanisms of DTA-1-dependent depletion of CT26/NY-ESO-1 tumor-infiltrating Treg cells. The gene discussed is FOXP3; the disease is neoplasm.