IL17A and rheumatoid arthritis: Treg cells in RA patients show a decreased suppressive activity, which can be related to the potential of Treg cells to convert into Th1-like Treg cells, secreting interferon-gamma (INF-γ) as well as Th17-like Treg cells, secreting IL-17 (Haase et al., 2018; Fan et al., 2020b).