Jamaican Fruit-eating Bat (Artibeus jamaicensis) Interleukin-4 (IL-4) is a Th2-associated cytokine produced primarily by activated CD4⁺ T helper 2 (Th2) cells and other type 2 immune populations, where it plays a central role in regulating humoral immunity, alternative macrophage activation, and modulation of inflammatory responses. IL-4 signals through receptor complexes containing IL-4Rα and the common gamma chain (γc) or IL-13Rα1, activating JAK/STAT6 pathways that promote B-cell class switching, antibody production, and suppression of certain pro-inflammatory cytokines. In A. jamaicensis, a bat species known to host diverse viral pathogens with limited clinical disease, IL-4 is of particular interest for understanding how Th2-type responses contribute to immune balance, tissue repair, and regulation of excessive inflammation. Modulation of IL-4 signaling may influence the balance between antiviral Th1 responses and anti-inflammatory pathways, potentially supporting viral tolerance while minimizing immunopathology. Characterization of Jamaican Fruit-eating Bat IL-4 supports studies of bat immune polarization, host–pathogen interactions, and mechanisms of immune regulation in reservoir species. Investigation of IL-4 dynamics in this species enhances comparative immunology research and provides insight into conserved and divergent Th2 regulatory pathways relevant to allergy, chronic inflammation, and immune homeostasis in humans.