Ferret 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 ferrets (Mustela putorius furo), IL-6 plays a critical role in mediating acute-phase protein production, fever, leukocyte activation, and B- and T-cell differentiation during infection and inflammation. Ferrets are widely used as translational models for human respiratory diseases, and IL-6 is strongly induced during influenza virus, SARS-CoV-2, and other respiratory pathogen infections, where its expression correlates with disease severity, lung inflammation, and systemic immune activation. Dysregulated IL-6 responses contribute to immunopathology in severe viral disease, making it an important biomarker for monitoring infection progression and evaluating antiviral or immunomodulatory therapies. In animal health and biomedical research, characterization of ferret IL-6 and related cytokine family members supports studies of cytokine storm mechanisms, vaccine efficacy, respiratory immunology, and host-pathogen interactions, reinforcing the ferret’s value as a key model for human infectious and inflammatory diseases.