Regulation of IL-6 in FLS. Dose response analysis of IL-6 mRNA expression, determined by RT real-time PCR in (fibroblast-like synoviocytes) FLS isolated from K/BxN mice following treatment with (a) corticosterone (0, 1, 10, 100, 500, 1000 nmol/l) or (b) TNFα (0, 0.1, 1, 5, 10, 25 ng/ml). (c) Fold change in IL-6 mRNA expression in wild-type (WT) control FLS, C2C12, MC3T3-E1 and K/BxN FLS, determined by real-time RT-PCR. All mRNA data were normalized for levels of the housekeeping gene 18S rRNA and presented as fold change in expression (± standard error) relative to either untreated control or untreated WT con FLS. (d) IL-6 secretion into culture media (pg/ml/100000 cells, ± standard error) in WT con FLS, C2C12, MC3T3-E1 and K/BxN FLS, determined by specific ELISA. Both mRNA and conditioned media were collected at 16 hr following treatment with either control, TNFα (10 ng/ml) or corticosterone (100 nmol/l). *P < 0.05, **P < 0.001 versus respective untreated controls; #P < 0.05 versus untreated WT control FLS. Dose response experiments are the combined duplicates of two K/BxN FLS. All other data are the combined duplicates of three separate FLS lines, two WT control FLS lines, two C2C12 repeats and two MC3T3-E1 repeats.