CCL20 and rheumatoid arthritis: Th17 cells play an important role in RA pathogenesis, by synthesizing other cytokines and chemokines, including IL-17F, IL-22, INF-Y, TNF-α, granulocyte macrophage colony-stimulating factor (GM-CSF), and chemokine (C-C motif) ligand 20 (CCL20) [42].