interleukin8

Interleukin-8 (IL-8), also known as CXCL8, is a chemokine of the CXC family that functions as a potent chemoattractant and activator of neutrophils during the innate immune response. It is produced by a variety of cell types, including macrophages, monocytes, epithelial and endothelial cells, and fibroblasts, in response to inflammatory stimuli such as infections or tissue injury.

IL-8 is encoded by the CXCL8 gene. Its expression is upregulated by pro-inflammatory signals (for example, IL-1, TNF, and Toll-like receptor ligands) and by microbial products. The mature protein belongs to the ELR+ CXC chemokines, characterized by an NH2-terminal ELR motif that promotes receptor binding and, in some contexts, angiogenic activity. Multiple mature isoforms can be produced by proteolytic processing.

IL-8 signals primarily through two G protein-coupled receptors, CXCR1 and CXCR2, on neutrophils and other leukocytes. Receptor engagement triggers intracellular calcium mobilization and activation of signaling pathways such as MAP kinases and PI3K, leading to chemotaxis toward the source of IL-8, neutrophil activation, degranulation, and respiratory burst.

Physiologically, IL-8 concentrates neutrophils at sites of infection or injury to combat pathogens. Pathologically, excessive or dysregulated IL-8 production is associated with inflammatory diseases such as chronic obstructive pulmonary disease, inflammatory bowel disease, psoriasis, and rheumatoid arthritis, and with tumor progression through promotion of angiogenesis and metastasis. Elevated IL-8 levels can correlate with disease severity in sepsis and acute lung injury.

IL-8 can be measured in plasma or tissue samples and is studied as a biomarker in inflammation. Therapeutic approaches that target IL-8 signaling, including neutralizing antibodies and CXCR1/CXCR2 antagonists, have been explored in preclinical and clinical trials, but no IL-8–targeted therapy has become standard care.