FOXP3 and neoplasm: Furthermore, the elevated expression of Fas Ligand on the tumor endothelium mediates the selective killing of CD8+ Tumor Infiltrating Lymphocytes (TIL) allowing for a predominance of FoxP3+ T regulatory cells (Treg) to infiltrate the tumor microenvironment, demonstrating that the tumor blood vessels act as an immunological barrier promoting tumor tolerance [13].