Understanding inflammation in juvenile idiopathic arthritis: How immune biomarkers guide clinical strategies in the systemic onset subtype.

The translation of basic insight in immunological mechanisms underlying inflammation into clinical practice of inflammatory diseases is still challenging. Here we describe how-through continuous dialogue between bench and bedside-immunological knowledge translates into tangible clinical use in a complex inflammatory disease, juvenile idiopathic arthritis (JIA). Systemic JIA (sJIA) is an autoinflammatory disease, leading to the very successful use of IL-1 antagonists. Further immunological studies identified new immune markers for diagnosis, prediction of complications, response to and successful withdrawal of therapy. Myeloid related protein (MRP)8, MRP14, S100A12, and Interleukin-18 are already used daily in clinic as markers for active sJIA. For non-sJIA subtypes, HLA-B27, antinuclear-antibodies, rheumatoid factor, erythrocyte sedimentation rate, and C-reactive protein are still used for classification, prognosis or active disease. MRP8, MRP14, and S100A12 are now under study for clinical practice. We believe that with biomarkers, algorithms can soon be designed for the individual risk of disease, complications, damage, prediction of response to, and successful withdrawal of therapy. In that way, less time will be lost and less pain will be suffered by the patients. In this review, we describe the current status of immunological biomarkers used in diagnosis and treatment of JIA.