FOXP3 and asthma: Since previous work has shown that Treg cells can lose Foxp3 expression and acquire effector cell function (19–22) under inflammatory conditions, we performed an Ovalbumin (OVA)-induced asthma model in a dual color reporter mouse strain in which prior expression of Foxp3 can be fate mapped in vivo (23, 24) analyzed Treg cells from lungs (Figure 1a).