Update on cytokines in rheumatoid arthritis

There have recently been fewer publications describing novel cytokines in rheumatoid arthritis. In the present review we focus on cytokines not previously implicated in contributing to the pathogenesis of rheumatoid arthritis.

The detection of IL-17 and factors that drive the differentiation and expansion of ThIL-17 cells, particularly in mouse models, clearly place IL-17 as a potential therapeutic target in rheumatoid arthritis. The emergence of other novel cytokines, notably IL-20 and IL-22, is of interest, not least by displaying proinflammatory effects particularly on fibroblasts - in contrast to their family member IL-10, the most potent anti-inflammatory cytokine. IL-32 is also of interest, with proinflammatory effects both on myeloid and nonmyeloid cells.

It is unclear whether the novel cytokines described in the present review will influence clinical practise. The involvement of IL-17 in murine arthritis may not translate as effectively to human arthritis - the ultimate test is a clinical trial in humans. The lack of efficacy of a recent anti-MCP-1/CCL-2 trial in rheumatoid arthritis highlights this dilemma. Finally, while technological advances including microarray analysis have broadened the scope for cytokine detection in rheumatoid arthritis, these methods have yet to translate to therapy in the clinic.