Control of Regulatory T Cell Development by the Transcription FactorFoxp3

Regulatory T cells engage in the maintenance of immunological self-tolerance by actively suppressing self-reactive lymphocytes. Little is known, however, about the molecular mechanism of their development. Here we show thatFoxp3, which encodes a transcription factor that is genetically defective in an autoimmune and inflammatory syndrome in humans and mice, is specifically expressed in naturally arising CD4⁺regulatory T cells. Furthermore, retroviral gene transfer ofFoxp3converts naïve T cells toward a regulatory T cell phenotype similar to that of naturally occurring CD4⁺regulatory T cells. Thus,Foxp3is a key regulatory gene for the development of regulatory T cells.