Cytokines in juvenile chronic arthritis.

Cytokines are important mediators of the immune response as well as the inflammatory response. Those concerned primarily with cell growth, differentiation and activation of cells within the immune system are called interleukins, of which there are now 18. Exposure to antigenic and environmental stimuli causes T cells to differentiate and polarise into Th1 or 2-like cells with different cytokine profiles, and requiring different cytokines for differentiation (IL-12 for Th1 and IL-4 for Th2). Homeostasis is usually restored as these cells are mutually inhibitory. Autoimmune diseases have been associated with a persistent imbalance with more Th1-like cells, which are thought to contribute to pathology. With regard to juvenile chronic arthritis (JCA), there is some preliminary evidence of this imbalance in the oligoarticular subgroup. Imbalance of pro-inflammatory cytokines, IL-1 and TNF with their natural inhibitors has also been shown to contribute to persistence of inflammation. In the case of JCA, there has been some evidence that these imbalances could account for some of the disease phenotypes. Furthermore, the tendency to imbalance is genetically determined.