TH-17 cells are increased in rheumatoid arthritis (RA) synovial fluid (SF). Summary of flow cytometric analysis identifying the percentage of TH-17 cells in normal peripheral blood (PB) (n = 15–16), RA PB (n = 9) or RA SF cells (n = 12–14) that were untreated (no), treated with PMA plus ionomycin (P/I) only or P/I plus IL-23. The percentage of TH-17 cells in each sample was normalised to its IgG value. * represents p < 0.05, and *** represents p < 0.005 between the indicated groups. § or † at the top of the treatment groups for RA SF denotes significant differences (p < 0.05) compared with normal or RA PB, treated in the same way.