TGFB1 and colitis: However, the instability of Foxp3+ Treg cells in colitis has been identified, and multiple studies have demonstrated that the expression of Foxp3 in Treg cells isolated from inflammatory sites decreased, indicating a loss of Foxp3 expression (40), which may explain why the proportions of Treg cells increased in colitis mice, while the expression of Foxp3, Il10 and Tgfb1 decreased.