Mast cell activation and its relation to proinflammatory cytokine production in the rheumatoid lesion

Mast cell (MC) activation in the rheumatoid lesion provides numerous
mediators that contribute to inflammatory and degradative processes, especially
at sites of cartilage erosion. MC activation in rheumatoid synovial tissue has
often been associated with tumour necrosis factor (TNF)-α and interleukin
(IL)-1β production by adjacent cell types. By contrast, our in
situ and in vitro studies have shown that the production of IL-15
was independent of MC activation, and was not related to TNF-α and
IL-1β expression. Primary cultures of dissociated rheumatoid synovial
cells produced all three proinflammatory cytokines, with production of
IL-1β exceeding that of TNF-α, which in turn exceeded that of IL-15.
In vitro cultures of synovial macrophages, synovial fibroblasts and
articular chondrocytes all produced detectable amounts of free IL-15,
macrophages being the most effective.