Fragility of Treg cells has recently arisen as a hallmark of autoimmune diseases, with Treg cells rendered dysfunctional in their suppressive features whilst expressing pro-inflammatory cytokines, maintaining Foxp3 expression and acquiring Th cell-like phenotypes, with identical transcription factors used by Treg cells to inhibit specific types of immune response (84, 113, 116, 117, 163–165). The gene discussed is FOXP3; the disease is autoimmune disease.