SPI1 and rheumatoid arthritis: An inverse correlation between miR-155 and PU.1 expression in SF-derived B cells [r= −0.65; P=0.04; 95%CI (−0.38 to −0.88) Spearman Rank Correlation coefficient] (Fig. 5c) further supports the presence of an active interaction between miR-155 and its target in RA B cells.