Jamaican Fruit-eating Bat FLT3 Ligand (FLT3L, also known as Fms-like tyrosine kinase 3 ligand) is a hematopoietic growth factor belonging to the cytokine family that regulates the development, proliferation, and survival of hematopoietic progenitor cells and dendritic cells. In the Jamaican fruit-eating bat (Artibeus jamaicensis), FLT3 ligand is produced by stromal cells, activated T cells, and other immune-associated cells, where it functions in the bone marrow and lymphoid tissues to support hematopoiesis and immune cell development. FLT3L binds to its receptor FLT3 (CD135) expressed on hematopoietic stem cells and early progenitor cells, activating intracellular signaling pathways such as STAT5, PI3K–AKT, and MAPK, which promote cell survival, proliferation, and differentiation, particularly of dendritic cell precursors and lymphoid progenitors. In bats, FLT3L likely plays an important role in maintaining innate and adaptive immune cell populations, including dendritic cells that are critical for antigen presentation and antiviral immune responses. Because bats are natural reservoirs for several zoonotic viruses, including coronaviruses and other emerging pathogens, studying immune regulators such as FLT3 ligand helps researchers understand hematopoietic and immune system regulation in bat species, contributing to research on host–pathogen interactions, immune tolerance, and comparative immunology in viral reservoir hosts.