INPP5D and rheumatoid arthritis: We showed that increased miR-155 prevented the translation of its mRNA epigenetic target SHIP-1, and thereby removed its negative feedback control of inflammatory TLR and PI3K signalling, thus permitting sustained production of cytokines and chemokines by these macrophages.17 71 Most RA STMs express high levels of miR-155 and commensurately low levels of SHIP-1, which is in sharp contrast to macrophages from non-inflamed synovium where the majority lack miR-155 and have high expression of SHIP-117 (figure 3).