Figure 1.

muOSM stimulates IL-6 and MCP-1 protein production by primary mouse synovial fibroblasts. Primary mouse synovial fibroblasts were cultured in 24-well dishes and stimulated with increasing concentrations of muOSM (0 to 50 ng/ml) (A and B). Supernatants were collected after 24 hours, stored at −20°C and then analyzed for IL-6 by the B9 hybridoma proliferation assay (A) and for mMCP-1 by ELISA (B). In addition, activity was compared to other IL-6/LIF cytokines and IL-1 in separate cell cultures (C and D), stimulated as indicated with muOSM (OSM), mIL-6 (IL-6), mLIF (LIF), or mCT-1 (CT-1) at 20 ng/ml and/or mIL-1β at 5 ng/ml. Supernatants were collected and analyzed as above. Data shows the mean and SD of triplicate treatments in one of two separate experiments that gave similar results. One star indicates significant difference from control (P < 0.05), whereas two stars indicate significance at P < 0.01, assessed by analysis of variance as in the Methods section. n.d., (not determined). IL-6 levels were not determined in supernatants from cells stimulated with IL-6.