Comparison of the relative inhibitory activity of HIG-82-IL-1Ra+ cells to recombinant IL-1Ra in the presence of chronic IL-1β stimulation. Experiments were performed similar to those described for Fig 4, except that 2 × 104 rat dermal fibroblasts retrovirally transduced to constitutively express and secrete human IL-1β were added to each culture well instead of recombinant IL-1β protein. PGE2 and IL-1Ra concentrations in the conditioned media were measured at 24 hour intervals using ELISA. Experiments were performed in triplicate, and each data point repesents the mean value ± SD. *P < 0.05 versus corresponding IL-1Ra source at 24 hours. ELISA, enzyme-linked immunosorbent assay; IL-1Ra, IL-1 receptorantagonist; PGE2, prostaglandin E2.