FoxP3 gets a new gig

On page 1141, the one-trick transcription factor FoxP3 reveals a new function. According to Chang and colleagues, FoxP3 does more than just drive regulatory T (T reg) cell development; it also promotes the proliferation of developing thymocytes.

FoxP3 is required for the development of CD4⁺CD25⁺ T reg cells, which subdue the activation of conventional T cells and thus protect against chronic inflammation and autoimmunity. Mice and humans that lack FoxP3 develop a spontaneous, multi-organ autoimmune disease that has been primarily attributed to the lack of T reg cells. But one fact suggests that this explanation may be too simple. Irradiated mice that are reconstituted with FoxP3-deficient bone marrow do not develop disease, suggesting that FoxP3 also functions in nonhematopoietic cells.

Chang and colleagues now show that FoxP3 is...