FOXP3 and neoplasm: To determine whether enhanced anti-tumor immunity in Opnfl/flFoxp3YFP-Cre mice is Treg intrinsic, we transferred purified CD3+CD4+ and CD3+CD8+ effector T cells (T regulatory cells were depleted as we sorted Foxp3-YFP-) into Rag2−/− hosts along with Opn-deficient Tregs or wild-type controls (Figure 5a).