STAT1 and rheumatoid arthritis: Protein detection results indicated that, the JAK1-STAT1 signals in tissues were activated, besides, the levels of JAK1, STAT1, p-JAK1 and p-STAT1 in RA group were markedly higher than those in Control group, and the protein levels were further up-regulated in RA+KLF4 group, evidently higher than those in RA group (Figure 5D, 5E).