Commensurate with the increased miR-155 expression, synovial fluid-derived B-cells of RA patients showed reduced expression of the miR-155 target PU.1 in ACPA+ compared to ACPA− patients, and a reduced proportion of PU.1+ cells among the resident CD20+ cells in synovial follicles (121). Here, PRTN3 is linked to rheumatoid arthritis.