Fig. 4

IL-9 promotes differentiation of Th17 cells. a Bar graph shows rIL-9, RA SF can increase level of IL-17A in CD4+ (Th17) cells from healthy donor, decreased upon blocking with anti-IL-9 in RA SF (n = 6, one-way ANOVA analysis with Dunnett’s multiple comparison test is applied for statistical significance, *p < 0.05). b Representative FACS dot plots show frequency of IL-17A⁺ cells in both naïve (CD4 + CD45RA⁺) and memory (CD4 + CD45RA^-) T cell compartment (n = 3). c FACS plots show frequency of RORγt + T cells in healthy PBMCs in presence of rIL-9, RA SF, anti-(CD3 + 28). Addition of IL-9 blocking antibody in RA SF reduced the expression of RORγt (n = 5). d FACS plots show RORγt⁺CD4⁺ T cells in RA PBL and RA SF, cumulative bar graph shows RORγt⁺CD4⁺ T cells in RA PBL and SF (n = 10, unpaired t test, mean ± SEM, **p < 0.005). IL interleukin, IL-9R interleukin 9 receptor, PBL peripheral blood, RA rheumatoid arthritis, RORγt retineic-acid-receptor-related orphan nuclear receptor gamma t, SF synovial fluid, Th T helper