IL-6 and BAFF, which are regulators of B-cell activation15, 16 and are present at high levels in SF compared to PB regardless of histological pattern in synovial tissues in RA patients (Supplementary Fig. 4) are also able to significantly increase miR-155 expression in CD19+ cells after 48 and 72 h stimulation (1.5±0.34 and 3.70±2.21 fold change after 48 and 72 h BAFF stimulation and 2.10±1.37; and 3.90±2.50 fold change after 48 and 72 h IL-6 stimulation) (Fig. 4). Here, CD19 is linked to rheumatoid arthritis.