Mouse Interleukin-6 (IL-6) is a multifunctional pro-inflammatory cytokine and a central member of the IL-6 cytokine family—including IL-6, IL-11, IL-27, IL-31, leukemia inhibitory factor (LIF), oncostatin M (OSM), ciliary neurotrophic factor (CNTF), cardiotrophin-1 (CT-1), and cardiotrophin-like cytokine factor 1 (CLCF1)—which signal through receptor complexes containing the shared gp130 subunit to activate JAK/STAT and MAPK pathways. In mice (Mus musculus), IL-6 is produced by macrophages, dendritic cells, endothelial cells, fibroblasts, and other cell types in response to infection, tissue injury, and immune stimulation, where it regulates acute-phase responses, B-cell maturation, T-cell differentiation (particularly Th17 lineage development), hematopoiesis, and fever. Murine IL-6 plays a critical role in experimental models of sepsis, autoimmune diseases (such as collagen-induced arthritis and experimental autoimmune encephalomyelitis), inflammatory bowel disease, cancer, metabolic disorders, and viral infections. IL-6 knockout and transgenic mouse models have been instrumental in defining its roles in immune regulation, chronic inflammation, tumor progression, and cytokine storm syndromes. As both a biomarker and therapeutic target, mouse IL-6 is central to preclinical research evaluating anti-inflammatory agents, monoclonal antibodies targeting the IL-6/IL-6R pathway, and novel immunomodulatory strategies, making it one of the most extensively studied cytokines in biomedical research.