S100A8 and S100A9 are major leukocyte proteins, known as damage-associated molecular patterns, found at high concentrations in the synovial fluid of patients with rheumatoid arthritis (RA). A heterodimeric complex of S100A8/A9 is secreted by activated leukocytes and binds to Toll-like receptor 4, which mediates downstream signaling and promotes inflammation and autoimmunity. Serum and synovial fluid levels of S100A8/A9 are markedly higher in patients with RA than in patients with osteoarthritis or miscellaneous inflammatory arthritis. Serum levels of S100A8/A9 are significantly correlated with clinical and laboratory markers of inflammation, such as C-reactive protein, erythrocyte sedimentation rate, rheumatoid factor, and the Disease Activity Score for 28 joints. Significant correlations have also been found between S100A8/A9 and radiographic and clinical assessments of joint damage, such as hand radiographs and the Rheumatoid Arthritis Articular Damage score. In addition, among known inflammatory markers, S100A8/A9 has the strongest correlation with total sum scores of ultrasonography assessment. Furthermore, baseline levels of S100A8/A9 are independently associated with progression of joint destruction in longitudinal studies and are responsive to change during conventional and biologic treatments. These findings suggest S100A8/A9 to be a valuable diagnostic and prognostic biomarker for RA.
Arthritis, Rheumatoid/*blood/pathology/radiography ; Arthrography ; Biological Markers/blood ; Calgranulin A/*blood ; Calgranulin B/*blood ; Humans ; Joints/pathology ; Synovial Fluid/metabolism

<b>OBJECTIVEb>To investigate the expression of myeloid-related protein complex (MRP-8/14) in children with acute Kawasaki Disease (KD).

<b>METHODSb>A total of 41 children with acute KD and 40 age- and sex-matched control children with upper respiratory tract infection were recruited. Serum levels of MRP-8/MRP-14 complex were measured by ELISA, messenger ribonucleic acid (mRNA) abundance of MRP-8 and MRP-14 in circulating granulocytes and monocytes was determined by RT-PCR, and the number of circulating endothelial cells was determined by flow cytometry.

<b>RESULTSb>When the analysis was stratified according to the presence or absence of coronary artery ectasia in the KD patient group, serum levels of MRP-8/MRP-14 complex, MRP-8 and MRP-14 mRNA abundance in granulocytes, and the number of circulating endothelial cells were all significantly higher in KD patients with coronary artery ectasia than in KD patients without coronary artery ectasia (P<0.05). Serum levels of MRP-8/MRP-14 complex were positively correlated with the number of endothelial cells in the circulation (r=0.69, P<0.05).

<b>CONCLUSIONSb>Serum levels of MRP-8/MRP-14 complex are elevated in a positive association with the number of circulating endothelial cells in KD children with coronary artery ectasia, suggesting a causative role in the development of coronary artery lesions.

Acute Disease ; Calgranulin A ; blood ; genetics ; physiology ; Calgranulin B ; blood ; genetics ; physiology ; Child, Preschool ; Coronary Artery Disease ; etiology ; Endothelial Cells ; pathology ; Female ; Humans ; Infant ; Male ; Mucocutaneous Lymph Node Syndrome ; blood ; complications ; pathology ; RNA, Messenger ; analysis