FOXP3 and immune system disorder: Continuous expression of FoxP3 is needed to maintain lineage identity and function of mature Treg cells (Williams & Rudensky, 2007), such that attenuation or loss of FoxP3 expression leads to defective Treg suppressive function and conversion into effector cells, enhancing rather than inhibiting the immune disease state (Wan & Flavell, 2007; Zhou et al, 2009).