FOXP3 and polyendocrinopathy: Expression of the transcription factor FoxP3 is currently the main marker of Tregs.93 CD127 (the IL7 receptor) is negatively correlated with FoxP3.11,95 Importantly, mutations that render FoxP3 inactive in humans are responsible for immune dysregulation, polyendocrinopathy, enteropathy, and X-linked inheritance (IPEX).