Processing of interleukin-1 beta in synovial cells freshly isolated from patients with rheumatoid arthritis.

This study examined interleukin-1 beta (IL-1 beta) production by synovial cells from patients with rheumatoid arthritis (RA). Freshly isolated, plastic-adherent, synovial cells from ten of thirteen patients with RA secreted significant levels of IL-1 bioactivity, and the cells from five patients secreted more IL-1 beta bioactivity than IL-1 alpha bioactivity. Further, there was a relatively good correlation between IL-1 beta bioactivity and IL-1 beta converting enzyme (ICE) activity, suggesting that bioactive IL-1 beta is possibly generated through the action of ICE. Analysis of metabolically-labeled IL-1 by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), however, indicated that, although these cells contained both pre IL-1 alpha and beta intracellularly, they secreted predominantly pre IL-1 beta.