IL6 and rheumatoid arthritis: As indicated in Figure 8E; synovial organ (i) and fibroblast (ii) cultures stimulated with 300 ng/ml PDGF-BB for 24 h and 6 days, respectively, showed significantly higher levels of IL-6 that increased from a mean of 275 to 533 pg/ml [RA synovial fluid IL-6 = 1,365 pg/ml + 1,850 (42)].