SPI1 and rheumatoid arthritis: Overexpression of this miRNA induced by PU.1 inhibition was shown to positively regulate B-cell activation in RA, implying subsequent persistent production of autoantibodies.173 More recently, an in-depth analysis of miRNA expression profiles in blood CD19+ B cells revealed differences in the expression of 27 miRNAs between RA patients in remission treated with methotrexate (MTX) and healthy controls, and these miRNAs were predicted to target genes known to be crucial for B-cell development.174