For example, peripheral interconversion between Th17 cells and Tregs has been observed in the presence of IL-6 and TGF-β1 (Murphy and Stockinger, 2010), and a loss of Foxp3 expression along with regulatory functions has been observed in the context of lymphopenia (Tang et al., 2008; Lathrop et al., 2008). Here, TGFB1 is linked to lymphopenia.