JAK2 and rheumatoid arthritis: During the development of RA, interleukin-23 (IL-23) interacts with its receptor to activate the downstream Janus kinase 2 (JAK2) signal transducer and activator of transcription (STAT) signaling pathway and simultaneously induces the differentiation of CD4+ T cells into Th17 cells [3, 4], thus increasing the levels of IL-17 cytokines [5].