Role for IL-1 and IL-6 in stimulation of IL-7 production by chondrocytes. (a) Chondrocytes were pretreated with either an IL-6 neutralizing antibody or the IL-1 receptor antagonist, or the combination of the two inhibitors, and then subsequently stimulated with fibronectin fragment. After overnight stimulation media samples were collected and used for an inflammation antibody array. IL-7 spots are shown in red circles. (b) Chondrocytes were stimulated with either IL-1β (10 ng/ml) or IL-6/soluble IL-6 receptor (10 ng/ml and 20 ng/ml) or the combination of cytokines. Medium was collected and subsequently analyzed with an IL-7 ELISA.