Quantification of cytokine mRNA in primary-culture (n = 5) or repeated-passage RA-SFB (n = 7) and primary-culture or repeated-passage normal-skin FB (n = 6 each). Levels of mRNA (relative units) for the various cytokines were determined by semiquantitative RT-PCR and normalized to those of the housekeeping gene cyclophilin. Data are expressed as box plots showing the median and percentiles 25 and 75. The dotted line in each graph depicts the cytokine mRNA level in stimulated control cells (i.e. lipopolysaccharide-stimulated peripheral blood mononuclear cells for IL- 1β, IL-10, and TNF-α; and TNF-α and IL-1β-stimulated primary-culture normal-skin FB for IL-6, IL-15, and IL-18). Large, filled dots represent mRNA levels in individual patients outside the 25 th and 75 th percentiles. FB = fibroblasts; RA-SFB = rheumatoid arthritis synovial fibroblasts.