SMAD4 and rheumatoid arthritis: In contrast, in RA Treg cells, a strong positive correlation was observed between miR-26 and SOCS1 (r = 0.68, p = 0.02), between miR-31 and SMAD3 (r = 0.66, p = 0.04), and between miR-155 and SMAD3 (r = 0.62, p = 0.06) and SMAD4 (r = 0.66, p = 0.04).