The expression of protein inhibitor of activated STAT3 (PIAS3) showed negative correlation with the level of Th17 in rheumatoid arthritis (RA) patients, and mice model of graft-versus-host disease revealed that PIAS3 upregulates Th17 population and downregulates Treg population [16, 17]. The gene discussed is PIAS3; the disease is rheumatoid arthritis.