Induction of Foxp3 expression in T cells by cellulose acetate beads in vitro

Gene expression of transforming growth factor-beta (TGF-beta) is needed to induce expression of transcription factor forkhead box P3 (Foxp3), which is required for the development and function of regulatory T (Treg) cells. The number of circulating Treg cells and the level of Foxp3 expression increase during granulocyte and monocyte apheresis (GMA), a useful therapy for ulcerative colitis. However, the mechanism underlying GMA-induced Foxp3 expression is unknown. We found that the level of TGF-beta mRNA in peripheral blood mononuclear cells (PBMCs) was augmented just after treatment of peripheral blood with a GMA carrier, cellulose acetate beads, in vitro and that Foxp3 expression in PBMCs increased after culturing these cells for 5 days after the treatment. The augmentation of TGF-beta expression was observed in CD3(-) PBMCs but not in CD3(+) T cells. Furthermore, the increase in Foxp3 expression in T cells depended on co-culture with CD3(-) PBMCs. We conclude that cellulose acetate beads have an ability to induce Foxp3 expression in peripheral blood T cells via augmentation of TGF-beta expression in CD3(-) PBMCs.