Previously, we showed that the PD-1 expression on CD3 T cells surged around day 16 after GD2-BsAb treatment was started [21], while the neuroblastoma PDXs harvested on day 10 post-treatment had few FoxP3+ Tregs irrespective of treatment (Additional file 1: Fig. S14A). The gene discussed is FOXP3; the disease is neuroblastoma.