STAT4 and rheumatoid arthritis: STAT3 and STAT1 have been implicated in RA pathogenesis.90 The activation of STAT3 is predominantly triggeredby IL-6 and related cytokines that utilize the gp130 receptor subunit.These cytokines are abundantly expressed in the synovial fluid ofindividuals with RA.91 STAT3 can also activatethe STAT1-associated genes STAT4 and STAT6 in RA synovitis.