For example, in patients with untreated early rheumatoid arthritis high circulating levels of IL-20 and IL-24 discriminate seropositive individuals and predict bony erosion – a property lost after treatment initiation; these cytokines appear to be produced by monocytes activated by immune complexes, and in turn mediate osteoclast activation [31▪]. This evidence concerns the gene IL20 and rheumatoid arthritis.