Dolphin Interleukin-6 (IL-6) is a multifunctional pro-inflammatory cytokine and a key 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 utilizing the shared gp130 subunit to activate JAK/STAT and MAPK pathways. In dolphins, particularly the bottlenose dolphin (Tursiops truncatus), IL-6 plays an important role in regulating acute-phase responses, leukocyte activation, B- and T-cell differentiation, and systemic inflammation in response to infectious, inflammatory, and environmental challenges. Elevated IL-6 expression has been associated with bacterial and viral infections, fungal disease, wound healing, and exposure to environmental stressors or pollutants, making it a valuable biomarker for immune activation and overall health assessment in both free-ranging and managed populations. In marine mammal health and comparative immunology research, characterization of dolphin IL-6 supports studies of host-pathogen interactions, stress physiology, and immune adaptation to marine environments, while also contributing to translational insights, as dolphins share similarities with humans in longevity, chronic disease susceptibility, and complex immune regulation.