IL-6

Interleukin-6 (IL-6) is a pleiotropic, 21-28 kDa cytokine produced by T cells, macrophages, endothelial cells and fibroblasts during infection, tissue injury and inflammation. It binds the IL-6 receptor (IL-6R/CD126), and the complex associates with gp130 (CD130) to trigger classic signaling, while soluble IL-6R enables trans-signaling through JAK-STAT3, MAPK and PI3K cascades. IL-6 drives acute-phase protein synthesis in hepatocytes, B-cell maturation and antibody secretion, Th17 differentiation via induction of RORγt, and hematopoietic stem cell activation. Chronic IL-6 excess contributes to rheumatoid arthritis, Castleman disease, cytokine release syndrome and multiple cancers, making IL-6 or IL-6R blockade (tocilizumab, sarilumab) an effective therapeutic strategy.