Elevated Production of Interleukin-6 Is Associated With a Lower Incidence of Disease-Related Ischemic Events in Patients With Giant-Cell Arteritis

Background— Patients with giant-cell arteritis (GCA) who develop a strong acute-phase response are at low risk of disease-related ischemic events. Methods and Results— To assess the potential protective role of proinflammatory cytokines in the development of ischemic events in GCA, we measured tissue expression (66 individuals) and/or circulating levels (80 individuals) of interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), and IL-6 in patients with biopsy-proven GCA. Tissue expression was determined by quantitative real-time polymerase chain reaction and immunohistochemistry. Circulating cytokines were determined by enzyme-linked immunoassay. We found that patients with disease-related ischemic events had lower IL-6 mRNA levels (5.9±2.1 versus 27.6±7.8 relative units, P=0.013), lower IL-6 immunohistochemical expression scores (1.5±0.9 versus 2.7±1, P=0.001), and lower circulating levels of IL-6 (13.6±2.1 versus 24±2.4 pg/mL, P=0.002) than patients without ischemic complications. No significant differen...