Humans that carry mutations in the transcription factor forkhead box P3 (FOXP3) or have depletion in Tregs develop severe autoimmunity (Sakaguchi et al., 1995; Miyara et al., 2005; Toubi et al., 2005; Long and Buckner, 2011; Fujio et al., 2012). The gene discussed is FOXP3; the disease is Autoimmunity.