Rabbit Interleukin-4 (IL-4) is a Th2-associated cytokine produced primarily by activated CD4⁺ T helper 2 (Th2) cells, mast cells, and basophils in rabbits (Oryctolagus cuniculus), where it plays a central role in regulating humoral immunity, allergic inflammation, and alternative macrophage activation. IL-4 signals through receptor complexes containing IL-4Rα paired with the common gamma chain (γc) or IL-13Rα1, activating JAK/STAT6 pathways that promote B-cell proliferation, antibody production, IgE-associated responses, and suppression of Th1-associated cytokines such as IFN-γ. In rabbit health, IL-4 is particularly relevant in parasitic infections, allergic skin conditions, and respiratory inflammation, where Th2 polarization supports antibody-mediated defense and tissue repair but may also contribute to eosinophilic infiltration and chronic inflammation if dysregulated. Rabbits are widely used as experimental models for asthma, pulmonary inflammation, atherosclerosis, and ocular inflammatory disease, and IL-4 plays a key role in airway hyperresponsiveness and mucus production in allergic airway models. As a biomarker of type 2 immune activation and a functional mediator of Th1/Th2 balance, rabbit IL-4 supports translational research into cytokine-driven allergic disease, immune polarization, and development of targeted anti-cytokine therapies relevant to human inflammatory and atopic disorders.