The transcription factor Foxp family includes Foxp1, Foxp2, and Foxp3. The Foxp3 (50KDa)plays a key role in CD4(+) CD25(+) regulatory T cell function and represents a specific marker for these cells. Despite its strong association with regulatory T cell function, in humans little is known about the frequency of CD4(+) CD25(+) cells that express FOXP3 protein nor the distribution of these cells in vivo. FOXP3 may be a master regulatory gene and a more specific marker of regulatory T cells than other T cells.
