Fig. 1

Th9 cell frequency is higher in SF of RA patients. a Representative FACS plots show Th9 cell frequency in PBL (HC, OA, and RA) and SF (OA and RA). b Cumulative scatter plot shows frequency of Th9 cells in of RA (PBL and SF; n = 28), OA (PBL and SF; n = 10), HC (PBL; n = 15), significant enrichment of Th9 cells in SF of RA patients. c Significantly higher DAS28-ESR correlation with Th9 cell frequency in RA SF (r = 0.79, p = 0.0001) and RA PBL (r = 0.45, p = 0.02, n = 28). d IL-9 ELISA performed in plasma (HC; n = 15, OA; n = 10, RA; n = 20) and RA SF (n = 20), shows higher levels of soluble IL-9 in RA SF 9pt?>compared to autologous RA plasma (mean ± SEM, *p < 0.05, **p < 0.005, ***p < 0.0001). DAS28 disease activity score of 28 joints, ESR erythrocyte sedimentation rate, IL interleukin, OA osteoarthritis, PBL peripheral blood, RA rheumatoid arthritis, SF synovial fluid, Th T helper