Estrogenic effects on lymph node Th17 cells in collagen-induced arthritis and in antigen-induced arthritis. DBA/1 mice were ovariectomized, subjected to collagen-induced arthritis (CIA) (A–E), or ovariectomized estrogen receptor α–knockout mice (ERα−/−) mice and wild-type (WT) littermates were subjected to antigen-induced arthritis (AIA) (F) and treated with 17β-estradiol (E2; 0.83 μg/day) or placebo (A, B). The frequency of T helper 17 (Th17) cells in lymph nodes (LNs) of CIA mice (terminated at day 14, n = 10 mice/group; at day 23, n = 8 to 10 mice/group; at day 35, n = 7 to 9 mice/group). Data from day 14 is from one representative experiment out of three independent experiments in total; otherwise, single experiments were performed. Representative flow cytometry plots are shown in (A). (C) Frequency of Th17 cells in LNs of CIA mice (day 23, single experiment, n = 9 mice/group), with only 3 days of E2 treatment (days 20 to 22). (D
E) Frequencies of Th1 (D) and regulatory T cells (Treg) (E) in LNs of CIA mice (day 14, n = 10 mice/group; day 23, n = 8 to 10 mice/group; single experiments). (F) In AIA, frequency of Th17 cells in LNs (draining knee joints) was determined at day 14 (two independent experiments, in total n = 14 to 19 mice/group). To improve normal distribution of data, some data were log-transformed prior to statistical analysis (B, D and E). Arithmetic mean ± SEM is shown in all graphs. Student’s t-test was used (*P <0.05, **P <0.01).