Over the last few decades, microRNA-155 (miR-155) has emerged as a key proinflammatory regulator in clinical and experimental arthritis and in systemic lupus erythematosus (SLE), targeting specific mRNAs, such as PU.1, SOCS-1, TAB-2, and c-Maf [9,10,13]. The gene discussed is SPI1; the disease is systemic lupus erythematosus.