Upon receptor ligation, JAKs are autophosphorylated and recruit and phosphorylate members of the STAT family and many of the pro-inflammatory cytokines that are highly expressed in RA and are known to be regulated by the JAK/STAT signaling pathway, such as TNF-α; IL-1β, -6, -7, -8, -12, -15, -17, -23, and -32; IFN-γ; and GM-CSF [20,27]. This evidence concerns the gene CSF2 and rheumatoid arthritis.