STAT1 and rheumatoid arthritis: As it is well known that IL-1β enhances the expression levels of various inflammatory factors in RA-FLS through the activation of NF-kB/ERK/STAT1 axis, p38 mitogen-activated protein kinase (MAPK) and JUNK signaling pathways (22, 32, 33, 47), we compared the effects of IL-1β and p75NTR neutralization on inflammatory cytokine production.