FOXP3 and central nervous system cancer: Another study in canine gliomas determined the nature of the infiltration, differentiating between CD3 T cells and those positive for the Forkhead box protein P3 (FOXP3), a regulator of Treg cell gene expression, finding similar results with generally low numbers of Treg cells, although higher FOXP3 densities were found in high grade tumors (95).