IL-6
Pleiotropic cytokine bridging pro-inflammatory NF-κB signalling and the acute-phase response; principal downstream endpoint in inflammation research.
For laboratory and research use only — not for human consumption.
Interleukin-6 (IL-6) is a 21 kDa pleiotropic cytokine with an unusual dual identity — both a driver of chronic inflammation and a mediator of acute-phase hepatic response and regenerative signalling. It is produced by macrophages, T-cells, fibroblasts, and adipocytes in response to TNF-α, IL-1β, or PAMP stimuli, and signals through a heterodimeric receptor complex of IL-6R (membrane-bound or soluble) with the shared gp130 subunit. Downstream JAK-STAT3 signalling drives expression of hepatic acute-phase proteins (CRP, SAA, fibrinogen) and pro-inflammatory transcriptional programmes. Chronic IL-6 elevation is a feature of inflammatory bowel disease, rheumatoid arthritis, Castleman disease, and metabolic-inflammatory conditions — the mechanistic rationale for IL-6R-antagonist biologics (tocilizumab, sarilumab). In peptide research, IL-6 concentration is the second-tier NF-κB pathway readout after TNF-α: KPV, BPC-157, TB-500 fragment (LKKTETQ), and GHK-Cu all reduce IL-6 in LPS-stimulated macrophage models. Quantification by ELISA or multiplex in cell-culture supernatants and tissue lysates is standard.