Natural (n)Treg are able to maintain self-tolerance in the thymus (Sakaguchi et al., 1995), but (i)Treg cells can also be induced in response to infection by microorganisms, and are characterized by the expression of CD25, the transcription factor forkhead box P3 (FOXP3), and production of anti-inflammatory IL-10 and TGF-β (Jäger and Kuchroo, 2010). The gene discussed is FOXP3; the disease is infection.