Synovial fibroblasts are the main IL-26-producing cells in RA joints.

<p>(A) FLS from RA patients and healthy subjects (<i>n</i> = 3), and T cells and non-T mononuclear cells (isolated from RA SF cells and from PBMC of healthy subjects) (<i>n</i> = 3), were either unstimulated or stimulated with anti-CD3 plus -CD28 mAbs or soluble CD40L, respectively. IL-26 mRNA expression (expressed as relative mRNA expression) was analyzed by RT-qPCR after 6 h stimulation (left panel) and IL-26 production (in ng/ml) was determined by ELISA after 48 h stimulation (right panel). Results are expressed as mean ± SD, <i>n</i> = 3; *<i>p</i><0.05 (Wilcoxon matched-pairs signed-ranks test). (B) IL-26 (upper panel) and IL-6 (lower panel) were quantified by ELISA in the supernatants of FLS from healthy subjects and RA patients, stimulated or not with 50 ng/ml IL-1-beta and/or IL-17A. Results are expressed in ng/ml (mean ± SD, <i>n</i> = 3).