IL9 and rheumatoid arthritis: A recent Chinese study demonstrated that the expression of Th9 cells (CD3+CD8+IL-9+) in RA patients was significantly higher than in normal controls, and this expression was positively correlated with high disease activity, elevated erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), number of tender joints, the number of swollen joints, and RF [31].