Guinea Pig Interleukin-4 (IL-4) is a Th2-associated cytokine produced primarily by activated CD4⁺ T helper 2 (Th2) cells, mast cells, and basophils in guinea pigs (Cavia porcellus), 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), 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 guinea pig health and research, IL-4 is particularly relevant in models of allergic airway disease and asthma, where Th2 polarization drives eosinophilic infiltration, mucus production, and airway hyperresponsiveness. Guinea pigs are also used in infectious disease models, including tuberculosis and viral respiratory infections, where IL-4 influences the balance between protective Th1 immunity and Th2-mediated immune modulation. Excessive IL-4 expression can impair effective cell-mediated responses against intracellular pathogens while contributing to allergic inflammation and tissue remodeling. As a biomarker of type 2 immune activation, guinea pig IL-4 is important in studies of vaccine responses, allergy pathogenesis, and immune polarization. Characterization of IL-4 in this species supports translational research into Th1/Th2 immune dynamics, cytokine-driven airway disease, and development of targeted therapies relevant to human asthma and allergic disorders.