TGFB1 and Arthritis: Such evidence of Treg variability has also been previously seen upon Salmonella-CFA/I treatment of mice induced with arthritis, whereas both IL-10+ Foxp3+ CD39+ CD4+ T cells and TGF-β+ Foxp3- CD39+ CD4+ T cells were co-induced, and were also found to be interconvertible35.