PRTN3 and rheumatoid arthritis: To dissect formally the expression pattern of miR-155 in B-cell subpopulations, we investigated miR-155 expression in sorted HC and ACPA+ RA PB CD19+ cells and observed that double negative memory RA B cells (IgD-CD27-) show the highest expression of miR-155 compared to other B-cell subpopulations (Fig. 2e), suggesting that an increased level of miR-155 in RA PB and SF CD19+ cells is likely due to an increased number of double negative memory B cells.