Experimentally, naïve CD4+ T cell was isolated from RA patients, followed by lentivirus transfection, IMD 0354 treatment, SP600125 treatment, and polarization assay, then Th1, Th2, Th17 cells, and their related cytokines were detected; meanwhile, NF-κB, JNK, mTOR pathways were also measured. Here, MAPK8 is linked to rheumatoid arthritis.