Objective. Kawasaki disease (KD) is an acute vasculitis of childhood, predominantly affecting the coronary arteries. S100A12, a granulocyte-derived agonist of both the receptor for advanced glycation end products (RAGE) and Toll-like receptor 4 (TLR-4), is strongly up-regulated in KD. This study was undertaken to investigate the potential contributions of S100A12 to the pathogenesis of KD.Methods. Serum samples from patients with KD (n = 30) at different stages pre-and post-intravenous immunoglobulin (IVIG) treatment were analyzed for the expression of S100A12, cytokines, chemokines, and soluble markers of endothelial cell activation. Primary human coronary artery endothelial cells (HCAECs) were analyzed for responsiveness to direct stimulation with S100A12 or lipopolysaccharide (LPS), as assessed by real-time quantitative reverse transcription-polymerase chain reaction analysis of cytokine and endothelial cell adhesion molecule messenger RNA expression. Alternatively, HCAECs were cultured in conditioned medium obtained from primary human monocytes that were stimulated with LPS or S100A12 in the absence or presence of IVIG or cytokine antagonists.Results. In the serum of patients with KD, pretreatment S100A12 levels were associated with soluble vascular cell adhesion molecule 1 titers in the course of IVIG therapy (r s = −0.6, P = 0.0003). Yet, HCAECs were not responsive to direct S100A12 stimulation, despite the presence of appropriate receptors (RAGE, TLR-4). HCAECs did, however, respond to supernatants obtained from S100A12-stimulated primary human monocytes, as evidenced by the gene expression of inflammatory cytokines and adhesion molecules. This response was strictly dependent on interleukin-1β (IL-1β) signaling (P < 0.001).Conclusion. In its role as a highly expressed mediator of sterile inflammation in KD, S100A12 appears to activate HCAECs in an IL-1β-dependent manner. These data provide new mechanistic insights into the contributions of S100A12 and IL-1β to disease pathogenesis, and may therefore support current IL-1-targeting studies in the treatment of patients with KD.

ObjectivesThe International League of Associations for Rheumatology classification criteria define systemic juvenile idiopathic arthritis (SJIA) by the presence of fever, rash and chronic arthritis. Recent initiatives to revise current criteria recognise that a lack of arthritis complicates making the diagnosis early, while later a subgroup of patients develops aggressive joint disease. The proposed biphasic model of SJIA also implies a ‘window of opportunity’ to abrogate the development of chronic arthritis. We aimed to identify novel SJIA biomarkers during different disease phases.MethodsChildren with active SJIA were subgrouped clinically as systemic autoinflammatory disease with fever (SJIA syst ) or polyarticular disease (SJIA poly ). A discovery cohort of n=10 patients per SJIA group, plus n=10 with infection, was subjected to unbiased label-free liquid chromatography mass spectrometry (LC-MS/MS) and immunoassay screens. In a separate verification cohort (SJIA syst , n=45; SJIA poly , n=29; infection, n=32), candidate biomarkers were measured by multiple reaction monitoring MS (MRM-MS) and targeted immunoassays.ResultsSignatures differentiating the two phenotypes of SJIA could be identified. LC-MS/MS in the discovery cohort differentiated SJIA syst from SJIA poly well, but less effectively from infection. Targeted MRM verified the discovery data and, combined with targeted immunoassays, correctly identified 91% (SJIA syst vs SJIA poly ) and 77% (SJIA syst vs infection) of all cases.ConclusionsMolecular signatures differentiating two phenotypes of SJIA were identified suggesting shifts in underlying immunological processes in this biphasic disease. Biomarker signatures separating SJIA in its initial autoinflammatory phase from the main differential diagnosis (ie, infection) could aid early-stage diagnostic decisions, while markers of a phenotype switch could inform treat-to-target strategies.