Fig. 2.

Fibroblast-like synoviocytes (FLS) are primed by pro-inflammatory cytokines whether they are derived from inflamed or non-inflamed joints. FLS were stimulated (stim) for 24 h with either TNFα or IL-1α (10 ng/mL) before the stimulus was removed and cells were rested in fresh medium for 24 h. Cells were then washed and stimulated with 10 ng/mL of the same cytokine for a further 24 h. IL-6 secretion in response to the first and second dose was measured by ELISA. a Absolute concentrations of IL-6 in supernatants after the first and second exposure to TNFα (left) or IL-1α (right). b IL-6 secretion in response to the second dose, represented as a fold change from the response to the first dose (normalised to 1); n = 10 (5 from non-inflamed joints, 5 from joints affected by rheumatoid arthritis (RA)). Grey circles and connecting lines represent FLS from joints affected by RA. Black crosses and connecting lines represent FLS from non-inflamed joints. *p < 0.05; **p < 0.01 (Wilcoxon matched pair signed rank test)