CD4 and rheumatoid arthritis: It has been shown that STAT2 is involved in RA-associated inflammation through the combination of STAT1 and interferon regulatory factor 9 (IRF-9) to form a heterodimer transcription complex of interferon-stimulated gene factor (ISGF3).190 STAT4 regulates the balance of IL-12 and IL-23 and participates in RA inflammation through the differentiation of CD4+ T cells into Th17 and Th1 cells.