Abstract
CD25+ FOXP3+CD4+ T cells (Treg) have been considered to play an important role in immune tolerance against several tumor antigens. It has also been indicated that high-level expression of FOXP3 (FOXP3high) is sufficient to confer suppressive activity to normal non-Treg. Here, we showed for the first time that vascular endothelial growth factor receptor 2 (VEGFR2) is selectively expressed by FOXP3high but not FOXP3low Treg. Such VEGFR2+ Treg exist in several tissues including PBMC and malignant effusion-derived lymphocytes. In conclusion, VEGFR2 may be a novel target for controlling Treg with highly suppressive function.