Rabbit GM-CSF (Granulocyte–Macrophage Colony-Stimulating Factor, CSF2) is a hematopoietic cytokine belonging to the colony-stimulating factor family, which also includes G-CSF (CSF3) and M-CSF (CSF1) that regulate the development, proliferation, and activation of myeloid immune cells. In rabbits (Oryctolagus cuniculus), GM-CSF is produced by activated T lymphocytes, macrophages, endothelial cells, fibroblasts, and epithelial cells in response to infection, inflammatory cytokines, or immune stimulation. Rabbit GM-CSF binds to the GM-CSF receptor (CSF2R) on hematopoietic progenitor cells and mature myeloid cells, activating intracellular signaling pathways such as JAK/STAT, MAPK/ERK, and PI3K–AKT, which promote the proliferation and differentiation of granulocytes, macrophages, and dendritic cells, while enhancing their phagocytic and antigen-presenting functions. In rabbit immunity, GM-CSF contributes to innate immune responses and inflammatory regulation, particularly through activation of neutrophils and macrophages during infection. Rabbits are also widely used as animal models for studying inflammatory and infectious diseases, and GM-CSF–mediated immune responses have been examined in rabbit models of bacterial pneumonia, where enhanced macrophage and neutrophil activation contributes to improved pathogen clearance and regulation of lung inflammation, providing insights relevant to host defense mechanisms and therapeutic strategies for respiratory infections.