Flow cytometry analysis of CD4+CD25+/highCD127low/-regulatory T cells in all compartments from rheumatoid arthritis and osteoarthritis patients. Peripheral blood (PB), synovial fluid (SF) and synovial membrane (SM) CD4+ T cells were analysed by flow cytometry after staining with fluorescein isothiocyanate (FITC)–labelled monoclonal antibody (mAb) against CD4 (clone RPA-T4), phycoerythrin-labelled mAb against CD25 (clone M-A251) and peridinin chlorophyll protein complex cychrome 5.5–labelled mAb against CD127 (clone RDR5; eBioscience). Representative dot plots for one RA patient and one OA patient are shown. The cells in these analyses were gated for lymphocytes via their forward and side scatter properties and further for CD4+ cells by positive anti-CD4-FITC staining (first column for each group). The red gates in the second columns indicate the CD4+CD25+/highCD127low/- regulatory T cells. These cells are back-gated and shown as the red CD4+CD25+/high population in the first columns of each patient group.